Infinity Focus Adjustments for Cameras

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from rollei mailing list:
Date: Sat, 14 Mar 1998 
From: Richard Knoppow
Subject: Re: [Rollei] Infinity Focuus on Rolleiflex 2.8F

you wrote:
>>> >a good camera repair tech can use a culminator to re-calibrate
>>> >the infinity setting on your camera   

  The focus can be disturbed in a couple of ways.  One, the focus knob got
loose and the infinity stop is wrong. Two, the finder lens is out of
coincidence with the taking lens.  Three, the ground glass has become
displaced somehow.  It is spring loaded and can be pushed in a bit.  If
there is a fresnel sitting on top of it that can push the glass down enough
to disturb the focus.
  Checking what has happened requires a piece of ground glass to fit the
film gate of the camera. The coincidence of the two lenses can be checked
at any distance by seeing of the images are focused at the same time.
Setting infinity requires either a collimator or an object at sufficient
distance to approximate infinity.  For a Rollei lens 1000 feet is enough.
  Its possible for a lack of coincidence to be due to damage to the front
of the camera. It really needs to go to a specialist like H.Fleenor (who
has my beat-up 2.8E at the moment).        
Richard Knoppow
Los Angeles,Ca. 

from rollei mailing list: Date: Fri, 13 Mar 1998 From: "Harry M. Fleenor" Subject: Re: [Rollei] Infinity Focuus on Rolleiflex 2.8F >Again, another newbie question for which I beg the indulgence and >request the benefit of the experience of those wiser. > >Turning the focus knob of my Rolleiflex to the stop for infinity seems >to leave the image slightly focused *beyond* infinity. Using the >magnifier, objects at infinity seem to become snappier as I back off >from the stop just a hair. > >Is this normal? Should I ignore the finder image and just go with the >measured value on the distance scale (the stop)? Or should I focus and >go with the finder screen? Hello John, Your focus adjustment is off and needs to be readjusted. It should exactly focus the sharpest at infinity right at the stop. Thank You Harry Fleenor ------------------------------------------------------------------------ Repairing Rollei TLR, SL66, Rollei 35, A110, SL35, A26 30 years experience including 15 in the Rollei factory service center. OCEANSIDE CAMERA REPAIR 909 AVIATION BLVD. #4 MANHATTAN BEACH, CA 90266 310-374-6506 ------------------------------------------------------------------------

From rollei mailing list: Date: Fri, 13 Mar 1998 From: Scott Goodwin Subject: RE: [Rollei] Infinity Focuus on Rolleiflex 2.8F I made the same observation with my 2.8F. Showed it to my camera repair friend who pointed out that "infinity" is a lot farther away than one might think. If you point your camera at something REALLY distant, like say the moon, you will find that the object is in focus with the focus knob all the way to the infinity setting. If you find that this is not the case, a good camera repair tech can use a culminator to re-calibrate the infinity setting on your camera. Having shot 35mm for so many years, it IS kind of frustrating to have to carefully focus for a shot that would not require focusing on most 35mm's. > -----Original Message----- > From: John [] > Sent: Thursday, March 12, 1998 > To: > Subject: [Rollei] Infinity Focuus on Rolleiflex 2.8F > > Again, another newbie question for which I beg the indulgence and > request the benefit of the experience of those wiser. > > Turning the focus knob of my Rolleiflex to the stop for infinity seems > to leave the image slightly focused *beyond* infinity. Using the > magnifier, objects at infinity seem to become snappier as I back off > from the stop just a hair. > > Is this normal? Should I ignore the finder image and just go with the > measured value on the distance scale (the stop)? Or should I focus > and > go with the finder screen?

Date: Thu, 12 Mar 1998 From: Evan Ludeman To: Koni-Omega Mailing List Subject: Re: [KOML] Question on Range Finder >Is the following item an indication that my range finder needs repair >or is this an undocumented feature available for no extra charge? The >yellow superimposed image in the rangefinder will aligh left to right >with the actual image by focusing. The image will never align top to >bottom. This is not a problem standing in the way of the "Unified >Theory", but I am curious to know if this is commen. Thanks I think some vertical misalignment is pretty common. As long as it doesn't impair proper focusing it wouldn't bother me. I didn't buy my K-O for the view through the viewfinder, after all :-).

Date: Mon, 16 Mar 1998 From: Kim or Adrian Diaz To: Koni-Omega Mailing List Subject: [KOML] Question on Range Finder Adjustment " ---Bob Erdman wrote: You can adjust the rangefinder yourself! On the back of the camera to thr rightof, but even with the viewfinder eyepiece there is a little flat plate that can be removed with a small spanner! The rangefinder mirror adjusting screw is behind that. It takes a small flat screwdriver. Bob." I tried this. (Kid's make sure your parents help you!) The adjustment changes the image left to right. Not exactly the direction I was looking for. Is there a way to move the image up and down without throwing off the focusing?

Date: Mon, 16 Mar 1998 
To: Koni-Omega Mailing List
Subject: Re: [KOML] Question on Range Finder Adjustment

To move the vertical adjustment screw you must take the top of the camera
off which is not hard to do.  Remove two screws on the left side (one of
which is reached through a hole in the carrying strap mounting plate),
plus one on the right side and one (pointing up) underneath the viewfinder
at the center rear (you have to remove the magazine to see it.  If I
recall correctly, the adjustment screw is just behind and to the right of
the little pivoting mirror and on mine it is sealed with a drop of paint. 
I'm not sure it's worth fiddling with.  Have you tried moving your eye up
and down relative to the viewfinder or tilting the camera a little bit
with your eye in the same place? 

Peter Caplow   

Date: Mon, 16 Mar 1998 From: David Stokes To: Koni-Omega Mailing List Subject: [KOML] Koni-Omega Rangefinder Adjustment (fwd) I'm forwarding a something I posted a while back concerning the rangefinder adjustment. I hope it helps. ---------- Forwarded message ---------- Date: Sun, 11 May 1997 From: David Stokes When I got my K-O Rapid the viewfinder's vertical alignment was off; I'm told this is not an uncommon thing. I had found a posting by Al Thompson to the Medium Format Digest that describes a method for adjusting this alignment. When he made the post, there was some disagreement about his method for adjusting the focus; however, I've made the vertical adjustment to my camera and checked the focus using this method. The rangefinder focusing is much easier to use, and the film results seem to indicate that the method for checking/adjusting the focus are accurate. This may be common knowledge, but here's Al's original post with some comments specific to the (Non-M) K-O Rapid that I've added: -David

From: Date: Sat, 24 Feb 1996 Subject: Koni-Omega rangefinder adjustment I've gotten a lot of queries on Koni-Omega rangefinder adjustment. I'm submitting this to MFD so I don't have to make so many individual responses. This information isn't available anywhere else that I'm aware of. If you are brave, have a lot of time, and want to check the rangefinder adjustments, here's what I did, if it will be of any help: (I am submitting this to MFD in case anyone else can benefit from it.) First, be sure you have the necessary small screwdrivers, with blade-thin driver points that will fit into the narrow screw slots. If your eyes are getting a bit weak with age, get some jewelers adjustable headband magnifiers from a jewelry supply store. You'll find they come in handy for many other things, too. You'll also need a good pair of fine-tipped tweezers to pick up and position screws. Lastly you will need a small light-colored dish or bowl to hold loose screws so they aren't lost. Don't forget to put out the cat, who will be interested in what you are doing and will jump into the middle of things at the most delicate moment. Work on a clean, flat, clear, well-lit surface. Place all removed parts in the dish or bowl when they are removed. 1) Remove the film back assembly. [ not necessary for the Koni-Omega Rapid ] 2) Using a coin or large screwdriver, remove the two large screws that secure the hand grip to the body. Removal of the grip will reveal two small screws retaining a silvered channel-shaped cover. This cover protects a flange and spring that retains the left side of the film-holder back. Remove the two small screws and the channel-shaped cover, along with the silvered left strap holder, which is also retained by the two small screws. You are now ready to remove the rangefinder/viewer cover. [ for the Koni-Omega Rapid, there is only 1 large screw that holds the grip; also, the strap is attached to a plate on the base (you don't have to remove the strap - just let it hang) ] 3) The rangefinder/viewer cover is held on by four small, black, slotted screws. With the back of the camera facing you, remove the two cover retaining screws at the left end of the cover. Now remove the single cover retaining screw at the right end of the cover, just beside the focusing knob. Lastly, remove the screw under the lip of the cover, in the center of the body. (This screw can't be seen with the film holder in place.) After removing the four retaining screws, lift up on the rangefinder/viewer cover and remove it. You are now ready to adjust the rangefinder. [ for the Koni-Omega Rapid the viewfinder cover is held on my 3 not 4 screws - (with the back facing you) 2 on the left and 1 on the right side; there is not a screw under the lip of the cover ] 4) The two screws for lateral and horizontal adjustment are on the right side of the camera body top. They should be self explanitory. The vertical screw at the outer right adjusts the vertical alignment of the split image. The horizontal one to its left adjusts the horizontal alignment of the same image, matching it to the range indicated by the numbers on the range adjustment knob and the image projected on ground glass or wax paper at the film plane. [ the two screws used to adjust lateral and horizontal alignment are not exactly as I pictured them, but if you look at the mechanism you can figure it out; the horizontal alignment screw is a set screw that runs perpendicular to the back of the camera; the vertical alignment screw runs perpendicular to the top of the camera and adjusts the angle of a mirror on the right of the rangefinder assembly; there may be an epoxy that "locked" these screws in place; I removed it with an exacto knife before adjusting the screw ] 5) Tape a ground glass across the open film plane back. If you dont have ground glass (and most people don't), you can use wax paper, taking care that it is stretched tight with no wrinkles. In a pinch you can even use a strip of wide frosted tape across the center area. It is representing what the film will see during an exposure. Turn the focus knob all the way to "infinity." (If it doesn't stop right on infinity you will have to loosten its set screws and re-position it. That's another problem, altogether.) With the shutter set on B (bulb) and the iris set wide open, cock the lens via its lever underneath, and press the firing button, holding the shutter open. Aim the camera at a distant light pole or other distant object. Observe the image projected on the ground glass. It should be sharp because the lens is at infinity. Continue to hold the button in and look at the same object through the viewer. The split images should be exactly superimposed. If they are not, turn the horizontal adjustment screw to the right or left until the images superimpose at infinity, matching the image projected on the glass/paper/tape. Make the same comparison of projected image with that in the split image viewer, this time looking for vertical misallignment. Adjust the other screw (far right) if necessary, for perfect vertical superimposition of the split image. 6) Reassemble in reverse order. Remember, small brass screws are easy to strip and difficult to replace. Don't play Sampson with them. Tighten them just enough to secure everything according to size and function, no more. Take special care not to scuff the screw heads. Treat them like jewelry. Once the camera, rangefinder, and focusing knob are synchronized at infinity, the closer settings should track OK. I had to loosten the focusing knob on my camera and re-position it to get it to read accurately. This should be done at both infinity and close-up settings, using a yard stick to measure and compare the closest indicated setting number (in feet) and the distance of a nearby object from its film plane image projection. Hope this helps any brave soul wishing to do their own rangefinder adjustments on a Koni-Omega. - Al Thompson -------------------------------------------------------------------------- _________________________________________________________________________ | David Stokes |"If the reader finds here something | | Georgia Institute of Technology | good, let him give thanks to God the | | | only Author of good. And what evil he | | (404) 876-1432 | finds, let him pardon my infirmity." | |_________________________________|___________________________ - Pascal __|

Date: Thu, 26 Mar 1998 From: "Thornton, Russ #CSR2000" Subject: RE:Messing aroung where I shouldn't... Why do you think that when you are in focus at infinity you will be in focus at portrait distance? I had a similar problem with my Bronica. I did not have any local techs that understood this either. They all said that it focused on infinity so it must be right. It would focus fine at infinity but when I took a picture of a subject at around 10 feet, the image was in focus on the viewer but the negative showed the focus to be a few inches behind. This is because the DOF is much shallower close up. Do this test to see if you are OK: Put the camera on a tripod by a well lit table. Set up a yardstick and a target(I use a box of film) such that the yardstick is extending away from the lens and the 18" mark is a few inches farther away than the closest focus distance. Place the target at the 18" mark. Now set your exposure so that the lens is wide open. Focus your camera on the target and snap a picture. Some times I focus a little ahead and snap one and focus a little behind and snap one. If you do this keep good records so you don't get confused. Now develop the film and inspect the image. If the image intended to focus exactly on the target is exactly on the target then you are OK. If not you will have to make adjustments. I can pretty much guarantee that ever Bronica S2A will fail this test. I find this a much better test of focus alignment that an infinity test. Russ Derek Zeanah wrote: I traded for a late '50's 500C a short while ago, and I got back the first few rolls of film today (portraits). In _every_ frame (36), focus is crisp and perfect about 1 foot _behind_ my subject. No big deal as far as the client was concerned (we were also shooting with Bronica gear), but I was really upset. I figured it was probably going to have to go into the shop anyway, so I might as well fiddle around and see if I could fix it myself. Symptoms pointed to the focusing screen, so that's what I played with. After a couple of tries...I think I got everything to work correctly. A checked focus at infinity and everything looked good, then I measured 3' from the =v= symbol on the 12 back to the focus target, focused, and came up with exactly.....3 feet (as indicated on the lens). Perfect as far as I can tell. The only thing that's different now from an hour ago is that all four screws are now tighter than they were (they seemed fairly loose when I started). Do the screws that hold in the focusing screen generally loosen up over time, or is this the result of a bad service (1 year ago, very few shots taken with this body since then, and those were all with flash)? Is there anything else I should check, or does good close and infinity focus mean the thing is close to dead-on now? Should I sent it in for service soon anyway (the screen in it now is a Beattie -- can't justify the Accumat upgrade as easily)? In the future, would it be wiser to pay someone else to do it, or try myself? -------------------- Russ Thornton Email:

Date: Thu, 26 Mar 1998 From: Derek Zeanah< Subject: RE:Messing aroung where I shouldn't... you wrote: >Why do you think that when you are in focus at infinity you will be in >focus at portrait distance? Actually, I assumed (wrongly) that in focus at the extremes (infinity and 3') meant in-focus at all ranges. Shot another roll and was still off... Went to the local camera shop (Peachtree Camera Repair) and borrowed a good back and tried again -- this time focus was still off, but not by a number of feet -- now it's that the eyelashes are out of focus, but the hairs on the sides of someone's head are crisp. (grins) Still trying to avoid the $120 fix, I tried again. Putting the screen in properly again meant good focus at 3' and infinity, but I discovered that minor adjustments of the focusing screen screws made a measurable difference on where focus fell in the mid-range. Originally, 9' by tape measure was 15' on the lens; after a few adjustments I've got it down to approximately 9 feet on the lens. I'll fiddle more in today's (wonderful) sunshine and try to get everything perfect. Everything is still fine at infinity, 3', and 5'. Now, I've got at least one back that needs to be fixed. Any thought on whether it's worth $85 to fix an old 12 back? What about the same to fix an old '12' back without matching inserts (the backup I'm testing today)? Do backs screw up often, or can I trust a rented A24 to function perfectly?

Date: Wed, 17 Jun 1998< From: Todd Belcher Subject: Re: [Rollei] Automat pressure plate oddity? Tom, Check the lens for shaprness by opening the f stops fully to 3.5 and locking the shutter open on "B". Open the back. Put a piece of ground glass on the film opening and set the camera to infinity. With a loupe check the ground glass for sharpness of image (rough side in). If you don't have a ground glass you can take the waist level finder off and remove the ground glass. It's fairly easy to do, quite straight forward. This will tell you whether or not the lens or lens board is the problem. As Richard notes, the front of the Rollei is only a cover, the real lensboard sits inside and may be mal-adjusted. On some Rolleis the pressure plate is removable. On old Rolleis you can see the screws on the back of the camera that hold the pressure plate on. On later cameras the screws are underneath the leather, on still later cameras the pressure plate is riveted on. I can't remember if the Automat 4 is a riveted on plate. Todd

From: Newsgroups: Subject: Re: How to check focus alignment? Date: Sat, 22 Aug 1998 > Hi Mike, > > Well, I did the repair after reading up on the innards of the > camera, doing some research, and getting Romney's part diagrams. ere are > the details of my disassembly: > > - Remove dials/shutter button, film advance assembly, rewind assembly > > - Remove top cover > > - Remove electronics and meter/metering LED piece > > - remove prism assembly (with screen attached) > > - There is a little square 'cup' that holds the screen. This slides onto > the prism and snaps into place via a pair of pins on either side of the > prism. I replaced the entire cup with a cup from another body. This body > looks like it's a slightly newer production than the one I was repairing > (both same model). > > - put everything back together. > > Now, I have a hunch that the distance from the focusing screen and the > prism may play a part in my problem. There is one square frame between > the prism and 'cup.' A pair of screws anchor the prism to this frame and > you can adjust the height of the prism. Other than these screws, I see no > way that you can adjust the position of the focusing screen - there is > only one position possible. The prism is as close to the screen as it > will go. Could it be that the prism is not far enough away from the > screen? > > I did not take anything out except the prism/screen assembly, and screwed > it back in exactly as it was. So I can't figure out what the problem > might be other than the prism or mirror being out of alignment. (or the > lens). > > I haven't done any film tests yet... I guess that is my next step in > determining whether this is a true problem. I was just hoping to discern > a problem first without wasting a roll or two of film. > > Oh yeah.... out-of-focus regions have the same degree-of-out-of-focus > throughout as far as I can tell, so it is probably not film plane > alignment. > > Thanks for your help. > C h r i s t o p h e r S. O w n The distance between the prism and the focusing screen is not critical in most SLR cameras. Unlikely to be a problem. Cut a small piece of ground glass so you can put it inside the camera resting on the film rails. Set the shutter on B and hold it open. Focus on a target of some sort in bright enough light that you can see very clearly on the ground glass. Use a loupe or magnifier. Then check focus through viewfinder to see if it is the same. If it is, then check several distances. If no problems, then you are OK and haven't wasted a frame of film. If you don't have ground glass, get some frosted mylar (drafting supply and art supply stores sell it). It is not rigid, so you will have to stretch it and tape it to make sure it is really flat. Put frosted side toward the camera lens. Bob Shell

From Rollei Mailing LIst: Date: Sun, 21 Nov 1999 From: Paul Roark Subject: Re: [Rollei] in re slight out of focus at infinity Sheldon Stokes wrote: >>In the absence of a collimator, the thing to do is put a ground >>glass on the back of the camera and check focus ... > >Actually a piece of scotch tape carefully pulled across the film guides can >work well too. I've used scotch tape on clear glass as a method for checking film plain sharpness on my Rolleis for some years. The tape has an extremely fine "grain" that transmits very high resolutions, unlike some ground glass I've used. With the plane glass as support, you can easily use an 8x loupe or even a 30x Edmund magnifier in order to see the relative sharpness of the fine detail. Paul Roark

From Rollei Mailing List Date: Mon, 22 Nov 1999 From: "G. Lehrer" Subject: Re: [Rollei] in re slight out of focus at infinity ..... Paul & RUGers Be careful to assure that the Scotch Tape is applied to the lens side of the glass sheet to ensure that it is in the actual film plane Jerry

Date: 03 Aug 1999 From: (FLEXARET2) Newsgroups: Subject: Repairing focus on Agfa folder This is one simple repair. Don't fret. Most simple folders that focus, have front element focusing. Usually a round ring is attached to the front turning element with very small screws around the side circumference. You will need a strong but tiny bladed screwdriver to unscrew these. Then the front ring should come off. You will need a channel wrench pliers to grasp the metal mount around the front element. Turn gently but firmly counter-clockwise. (Check front ring and focusing scale to see that is the direction to turn it to unscrew the front element. Once you get it off you may want to clean the lens elements with regular alcohol and Q-tips. Get a very light oil and put some drops in the screw threads and re-assemble the front element into the lens. Turn it back and forth to let the oil soften the dry lubricant and get it turning right. Put the shutter at B or T use a ground glass at the focal plane and a magnifier and focus sharply at an infinity target outside. One this is set re-assemble the front ring and set it to the infinity setting. The re-tighten the ring's screws and you are back in action able to set the lens at all focus settings. (If the front ring does not come off with three small screws around its outer circumference, there is some other simple way to get it off). This is one of the easiest camera repairs - old front cell focusing folders with frozen lubricant. For your efforts you can be rewarded with nice sharp medium format photos if you do it right! - Sam Sherman

Date: 03 Aug 1999 From: (Zxcvbob) Newsgroups: Subject: Re: Repairing focus on Agfa folder I can unscrew the front element once I remove the infinity stop, and I cleaned out the green grease with trichlorethane and replaced it with just a speck of silicone grease (high voltage dielectric grease, actually). Now the focus knob turns silky smooth, with just *exactly* the right amount of resistance. But, the front element only moves in and out a small fraction of a millimeter, and a ground glass shows that the camera stays focussed at infinity throughout its focus range. I can't detect any change in the focus. I would expect the front cell to move in and out several millimeters when rotated through its focusing range. bob

Date: 03 Aug 1999 From: (FLEXARET2) Newsgroups: Subject: Re: Repairing focus on Agfa folder You have probably cleaned and lubricated the screw in portion that is not supposed to turn. That probably has fine threads and should remain screwed into the shutter body. The focusing helix is coming out attached to the front element. The threads that move are coarse not fine. If that is the case when you remove the front element you will have to unscrew the focusing helix which is still attached to the back of the front element. Then you will see the larger threads and it will focus correctly. Be sure to clean any lubricant from the fine thread and screw that portion in tight into the shutter before replacing the movable front element into the focusing helix. - Sam Sherman

From camera fix mailing list: Date: Tue, 03 Sep 2002 From: "jonyquik" Subject: Re: Checking 35mm infinity focus Your questions are very good, but not so easy to answer in an email. My missives here have been getting quite long, and I am not looking to break any records. I will prepare a file with pics of me doing an optical alignment on a Canon FTb in the very near future, and it will take you step by step through a fool proof precedure to make sure the camera is perfect, including the only sane procedure to align the Flange Focal Distance of any camera. If that factor, which needs to be considered first in any setup of a 35mm camera, is out beyond the allowable tolerances, this camera CANNOT BE USED TO CHECK THE INFINITY SETTING of any lens. I would sooner trust the infinity setting on a lens, than the FFD of any camera. In the manufacture of 35 mm cameras, the lenses are set to infinity to a certain tolerance to assure interchangeability on 99% of all cameras. I cannot vouch that this is so with third party lenses, but with most of the manufacturers this is a standard. If the infinity setting is out on a lens, usually it is best to look for loose elements or seperations, with loose elements being the most common. --- In camera-fix@y..., "stuey63au" madfamily@b... wrote: > Hi. I suppose I should have explained myself. The reason for the use > of the ME focussing screen was because I'd noticed that no lens would > focus correctly at infinity on a particular Spotmatic F. So, to > determine whether it was the lens to film plane that was 'out', or > the focussing screen adjustment, I thought I'd use the method I > described. If my lenses (that focus correctly to infinity on my other > Spotmatic F) also focussed correctly on the test camera, I thought I > could reasonably assume that it was the screen or mirror that needed > attention - most likely the screen, as the screws do look like > they've been touched. Is this procedure flawed? > > I wasn't actually checking the lens, in other words, but the camera. > By the way, I have checked the lens to film plane distance with a > vernier (as discussed on another thread a while back) but the > procedure didn't feel like it was accurate, relying on a tentatively > poised vernier jaw *just* contacting the lens mount. Someone else on > this forum suggested using the depth gauge of the vernier through the > lens throat, too, but I haven't done this yet... >> Regards, and thanks for all the advice. > > Mark > > --- In camera-fix@y..., "ned99992001" nedsnake@e... wrote: > > All the factory service manuals will give the flange to film plane > > distance. If one does not know this distance then you can't align the > > lens mount, assuming it needs to be aligned. To check or adjust the > > infinty focus of a lens a simple piece of ground glass will work just > > fine. Many factory test set ups on both 35mm and medium format use a > > piece of ground glass. Of course the most accurate way to set the > > infinity focus of a lens is with a collimeter. > > Don't give camera's more credit than they are do, they are not the > > fine engineering marvels people some times think they are. > > Just my opinion. ...

From camera fix mailing list: Date: Tue, 03 Sep 2002 From: "leighamvale44" Subject: Infinity check Hi, I've started a new thread because the previous one was getting a mite long. Look forward to seeing the set-up with the FTb. Something was niggling me about this discussion, and I found what it was in the factory repair manual for the Exakta Varex IIb. I quote - and the translation from German is by my good friend and chairman of the Exakta Circle Tom Ackermann. "Adjust and check the distance between the lens mount and the film-way. Check along the film-way with a dial gauge. The distance between the lens mount and the film-way is 44.72mm plus or minus 0.01mm." So I have found a tolerance. What's interesting is that the manual says to check the lens flange distance from the film-way - presumably the flat plane of the film rails. This would seem to suggest that if any allowance is made for film curvature then this is 'built-in' to the quoted distance from the lens flange to the rails. In other words, the actual focus point of an Exakta lens is 44.72mm plus whatever that tiny allowance is. It goes on to say that the angle of the mirror must be checked with the collimator set to infinity. At infinity, if the image on the viewing screen is not at its sharpest, the angle of the mirror is adjusted by bending a small stop plate in the side of the mirror box, down if the maximum sharpness is obtained before the infinity mark, and up if the maximum sharpness is not reached at the infinity mark. This check should be made whenever a mirror or mirror carrier is changed. This must assume that the viewing screen is positioned accurately (?). I checked a few other cameras. On a Zenit, there's an adjustable screw stop for the mirror angle. On a Canon A1 there's stop nut (eccentric??). On a Canon F1 it looks as if the stop is adjustable but I don't feel like experimenting because both Canons focus accurately. I also see from Schneider's website, under Vintage Lens Data, that the 'Back Focal Length' (without any tolerances) is quoted for a range of lenses. Can we assume that this is the lens flange to film rail distance? If this is right, and holds good for other makers, then if we set the distance to the maker's figure, and use a lens which is known to have an accurate focus scale, then if it doesn't focus on the screen at infinity either the mirror angle or the position of the screen must be at fault ?? Is my reasoning sound, or am I missing something? Regards, Peter Wallage

From camera fix mailing list: Date: Wed, 04 Sep 2002 From: "jonyquik" Subject: Re: Infinity check Peter you are on the right track, but your reasoning fails you when you presume that the focus point of a lens is the FFD of the camera. It is not!!! The reason for the FFD adjustment is to assure interchangability with lenses of that mount, and the parallel setup allows corner to corner sharpness. The focus point of the lens is beyond the point where the filmway, as you call it, ends. In a multiple layered emulsion, the center layer is the desired point of focus. Talk to the folks at Nikon or Canon.

From camera fix mailing list: Date: Wed, 04 Sep 2002 From: Mario Groleau Subject: Re: Re: checking 35mm focus Hi, I use the method of the Scotch tape with success, be sure to use MagicTape, it is frosted, the image is form at the tape surface, like a ground glass and like on film emulsion. I use a 10x magnifier to verify focus, and it work very well. You have to verify 3 points, Infinity (very far object), 3m and 1m. For the two last you can mesure them with a mesuring tape and chez if the distance marking on the camera match with the real one. After, the adjustment method is different depend for each lens. If you have an SLR camera verify if the focus match with the one you make in the finder. For some bumped SLR the two focus do not match. Best regards Mario

From camera fix mailing list: Date: Wed, 04 Sep 2002 From: "jonyquik" Subject: Re: checking 35mm focus Gentlemen!!! We are talking about controlling the rays of light to form a picture within an emulsion chemically. A light wave can be measured and it is equal to 1/50,000,000ths of an inch. It can be seen, thus it can be controlled. The business of taking a sharp photograph is the business of splitting hairs. If not for that then why do we strive here to make these mechanical machines work??? In offset printing you have said it all, you are using large format film held flat by vaccums. This is the method used also in mapping cameras where the film is large enough to where it has much less natural tendency to curl. And you use a ground glass to focus the image, and that ground glass was placed into that position by someone who engineered that camera, not you. 35mm and 16mm film do not conform to the rules of large format film. Helping me to make my point quite ellegantly is the tolerance of 0.01mm given in this Exacta manual. Can any of you imagine 0.01mm??? Can you imagine 0.01 inches? We all know what an inch is. Do we know what a mm looks like??? It is 1/24ths of one inch. Less than 1/16th our more familiar American measurements. To measure 0.01mm, one needs to use a very sensitive, range limited dial indicator. I have a Swiss one that can measure in increments of 1/200mm. I also have a Swiss micrometer that can measure to 0.001mm. That is thousandths of a mm, not thousandths of an inch. All of my instrumentation is far more sensitive than this tolerance, so I am capable of setting it and reading it if I am skilled enough to use these instruments, which I can assure you 40 years of repairing optical equipment has given me that. To answer that bit about scotch tape, I have found that scotch tape measures pretty much from roll to roll is about .004 or 4 thousandths of an inch in makes quite good shim material. The thickness of this Fujicolor Super HQ film is 0.014 or 14 thousandths of an inch, it also makes good shim material. How many thousandths of that film do you suppose is emulsion. Remember that's inches your talking about, not mm. Yes call yourselves fixers, but optical repair is really the business of a camera repairman. Been there done that!!! --- In camera-fix@y..., "camfix55" camfix@w... wrote: > Hi Guys; > I have a background in offset printing. We used large sheets of film on a vacume back. I would focus the copy on a ground glass to get the sharpest image I could. close the back and shoot. I don't recall any allowance for emulsion thickness and while I don't question that this is a valid concerne I do wonder if we are splitting hairs here. If you could get a camera perfectly adjusted and aligned I would think that that adjustment would change with a different lens. Vincent, Wouldn't 1 layer of Scotch tape be far thicker than the emulsion on the film? A very confused. Everett

From camera fix mailing list: Date: Wed, 04 Sep 2002 From: "jonyquik" Subject: Re: Checking 35mm focus I am sorry I made a mistake measuring that Fuji film. It is 0.006 inches also. The mistake you continue making though is trying to lay a 35mm camera into the same design as your large format camera. Your 0.006 inch film is rattling around in a channel almost twice its thickness that is created by the difference in the height of those rails, the old Pressure Plate Rails, and the Film Rails. To the best of my reconning without dragging out the granite surface plate and the dial indicator, that distance on my depth vernier caliper is somewhere around 0.013 inches, and I think a layer of frosted scotch tape might just lay that focus in the right place. Your reasoning is flawed if you continue thinking that the film is layed perfectly flat against the film rails, it is not, but in the dead center it is rather relaxed back against the pressure plate, 0.006 minus 0.013, leaves about 0.007. Are we getting any closer to this kind of thinking here??? Perhapos a single layer of tape isn't enough. LOL!!! --- In camera-fix@y..., "camfix55" camfix@w... wrote: > Hi Vincent; > I would be the last person here to question your talent or experience. You have been a great contributor and I only ask out of ignorance not arogance. I measured the thickness on a roll of Kodak G100 with emulsion it measured .006. I then dug out some negs and measured a unexposed frame (slight tint) I came up with .0058 from this I surmised that the emulsion was .0002 thick. > so my question is wouldn't a piece of .004 scotch tape move you too far beyond the film plain? by my math this is 20 times thicker than the emulsion. Second question, considering that the Fuji film is thicker wouldn't this change the curvature or would it remain close enough to call it a constant? Respectfuly. Everett

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