A question about eyesight

Question:

This is a very interesting thread… but there’s one thing I don’t understand: Why would Nikon build the viewing system with a -1 value? Bob Scott Whitehall, NY

Because the focusing screen is about half an inch away from your eyeball when you are holding the camera. A -1 diopter, being a concave lens, optically projects an image of the screen ~3ft away, where most (but alas not all) people can focus their eye on it. — Use address below for Email replies. Address on Header is bogus to defeat AutoSPAM. Rudy Garcia The answers I have found have just served to raise a whole new set of questions. In some ways I am as confused as ever, but I believe I am confused on a much higher level and about more important things. Author unknown

Response:

I’ve talked with my opthomologist, who is also an amateur photographer, and in my particular case he doesn’t recommend ANY viewfinder correction. I have glaucoma (worse in my right eye), an astigmatism (worse in my right eye), 20/20 corrected left eye, and 20/60 corrected right eye. On top of all that, I have a fast-growing cataract in my right eye. Now, my right eye is my predominant eye, but I’ve started focusing with my left eye. I also wear bi-focals for normal wear and a separate set of bi-focals as computer glasses (I spend 6-8 hrs in front of a monitor each day). I posed the question to my doctor, and he recommended that I do nothing – he only recommends diopter correction if you are NOT going to wear glasses when focusing (and in my case my vision is so bad that it won’t help.) I use a Canon EOS 1, a Canon A2E, and a Mamiya 645 (waist level and prism) and wear my glasses when focusing. With the exception of the cataract fuzziness (milky coloration), I can focus without any problems using BOTH eyes – right for gross focusing, and left eye for critical focusing. – Hide quoted text — Show quoted text – Hi all, This might sound like a stupid question (and perhaps it is) but i’ll ask anyway. My eyesight is not too far below the 20/20 standard and I would like to know if, when my eye sees an image as being in focus (as indicated by the split image / pixelate type viewfinder), is it actually out of focus (with my eyesight not being 20/20. I do not use a correcting view piece. Hope you can help.

Response:

– Hide quoted text — Show quoted text – This is a very interesting thread… but there’s one thing I don’t understand: Why would Nikon build the viewing system with a -1 value? Bob Scott Whitehall, NY Because the focusing screen is about half an inch away from your eyeball when you are holding the camera. A -1 diopter, being a concave lens, optically projects an image of the screen ~3ft away, where most (but alas not all) people can focus their eye on it. —

As I mentioned in an earlier post, the Nikon correction diopters are marked for the net of the built in -1 diopter optical system plus the diopter correction lens itself. Thus a +0.5 corrective lens is actually a +1.5 diopter. However, I caution the reader not to just go out and buy a corrective lens just on the above fact. There are apparently many other factors involved in determining how much diopter strength you’ll be comfortable with. For example, I am farshighted and my eyes test out as requiring a +2.75 prescription for comfortable reading and a mild +0.75 for distant viewing. Yet, I found through trial and error that, the optimum Nikon corrective lens for me is a +0.5. I never would have "backed" into that number by any math. The best way is to find a dealer who carries the corrective lenses and to see if they’ll let you try them. Good luck in finding the right corrective lens for you. — Use address below for Email replies. Address on Header is bogus to defeat AutoSPAM. Rudy Garcia The answers I have found have just served to raise a whole new set of questions. In some ways I am as confused as ever, but I believe I am confused on a much higher level and about more important things. Author unknown

Response:

This is a very interesting thread… but there’s one thing I don’t understand: Why would Nikon build the viewing system with a -1 value? Bob Scott Whitehall, NY

Response:

- Hide quoted text — Show quoted text – an optician’s +1 diopter is as marked, a lens of 1 meter focal length. A Nikon +1 diopter is not. Nikon marks its corrective eyepiece to show the resultant dipoter power, after taking into account that the optical path started with a -1 diopter correction. Thus a Nikon eyepiece marked +1 is not the same as a +1 diopter. It is a +2 diopter which when screwed into the viewfinder, nets out to +1 (-1 +2 = +1). Unfortunately, Nikon’s marking method is not well documented in their manuals (at least for the earlier manual cameras) and causes a lot of confusion and wasted money as people try to buy corrective eyepieces. This is explained in Carl Shipman’s 1986 book "How to Select & use Nikon SLR cameras" page 62. Hope this helps. AHA!!! This is EXTREMELY interesting! The reason it’s so interesting is, that I could NOT understand why, when my eyeglasses have a +2.5 correction that a Nikon +0.5 diopter would correct that! If you add -1.0 to +2.75, it turns out that a +1.5 diopter lens is what you should need, but with your explanation, it’s apparent that’s the reason the +0.5 lens works perfectly for me. Not well-documented? Hell, it’s a deep, dark secret! I have no idea why Nikon isn’t a little more free with information about their products. Well, you could still use an optometrist’s diopter lens to test with; find the one that works and subtract 1.0 from the lens value. N’ece se pas? Thanks for an extremely important piece of information, for me at least. Would you be familiar with Canon’s setup? For Canon viewfinders, a -0.5 diopter works for me. the prescription i received from my eye doctor reads -1.75. how does this translate into nikon optics? in other words, can i figure out what diopter i need from this information without another trip (and further expense) to said eye doctor? btw, i have an N70.

Add -1.0 to -1.75 and you get the total, -2.75. Now, since the diopter should be -2.75, you’d need a -3.75 diopter, if I understand this correctly. Of course, Nikon doesn’t make one like that, but the closest value is a -4.0. That should do it for you. (I think) As I understand it, ALL Nikon viewfinders are set to -1.0 diopters, no matter which camera you have. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

I think you have it backwards. I assume in all cases the question is what eyepiece correction is needed in addition to the correction of you eyeglasses – which would be true for near-sighted people who would want to have their glasses on to see when not looking through the camera. They would have some degree of minus correction in their eyeglasses. To adjust for the minus correction built into the viewfinder you need some degree of PLUS eyepiece correction. To use the viewfinder without your eyeglasses you would need some degree of MINUS correction. If my understanding is correct, the eyepiece correction needed in addition to eyeglasses that correct for distant vision would not vary with the eyeglasses but would be a constant and a function of the viewfinder optics. But if that were true, and the viewfinder was -1.0, then why would +0.5 work for both my Nikons? – Hide quoted text — Show quoted text – an optician’s +1 diopter is as marked, a lens of 1 meter focal length. A Nikon +1 diopter is not. Nikon marks its corrective eyepiece to show the resultant dipoter power, after taking into account that the optical path started with a -1 diopter correction. Thus a Nikon eyepiece marked +1 is not the same as a +1 diopter. It is a +2 diopter which when screwed into the viewfinder, nets out to +1 (-1 +2 = +1). Unfortunately, Nikon’s marking method is not well documented in their manuals (at least for the earlier manual cameras) and causes a lot of confusion and wasted money as people try to buy corrective eyepieces. This is explained in Carl Shipman’s 1986 book "How to Select & use Nikon SLR cameras" page 62. Hope this helps. AHA!!! This is EXTREMELY interesting! The reason it’s so interesting is, that I could NOT understand why, when my eyeglasses have a +2.5 correction that a Nikon +0.5 diopter would correct that! If you add -1.0 to +2.75, it turns out that a +1.5 diopter lens is what you should need, but with your explanation, it’s apparent that’s the reason the +0.5 lens works perfectly for me. Not well-documented? Hell, it’s a deep, dark secret! I have no idea why Nikon isn’t a little more free with information about their products. Well, you could still use an optometrist’s diopter lens to test with; find the one that works and subtract 1.0 from the lens value. N’ece se pas? Thanks for an extremely important piece of information, for me at least. Would you be familiar with Canon’s setup? For Canon viewfinders, a -0.5 diopter works for me. the prescription i received from my eye doctor reads -1.75. how does this translate into nikon optics? in other words, can i figure out what diopter i need from this information without another trip (and further expense) to said eye doctor? btw, i have an N70. Add -1.0 to -1.75 and you get the total, -2.75. Now, since the diopter should be -2.75, you’d need a -3.75 diopter, if I understand this correctly. Of course, Nikon doesn’t make one like that, but the closest value is a -4.0. That should do it for you. (I think) As I understand it, ALL Nikon viewfinders are set to -1.0 diopters, no matter which camera you have. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

– Hide quoted text — Show quoted text – Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass. Oh? I didn’t realize that. What would make an optician’s +1 diopter lens different than anyone else’s +1 diopter lens? This is not a belligerent question, but I am curious as to why you would say that. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography Chuck, an optician’s +1 diopter is as marked, a lens of 1 meter focal length. A Nikon +1 diopter is not. Nikon marks its corrective eyepiece to show the resultant dipoter power, after taking into account that the optical path started with a -1 diopter correction. Thus a Nikon eyepiece marked +1 is not the same as a +1 diopter. It is a +2 diopter which when screwed into the viewfinder, nets out to +1 (-1 +2 = +1). Unfortunately, Nikon’s marking method is not well documented in their manuals (at least for the earlier manual cameras) and causes a lot of confusion and wasted money as people try to buy corrective eyepieces. This is explained in Carl Shipman’s 1986 book "How to Select & use Nikon SLR cameras" page 62. Hope this helps.

AHA!!! This is EXTREMELY interesting! The reason it’s so interesting is, that I could NOT understand why, when my eyeglasses have a +2.5 correction that a Nikon +0.5 diopter would correct that! If you add -1.0 to +2.75, it turns out that a +1.5 diopter lens is what you should need, but with your explanation, it’s apparent that’s the reason the +0.5 lens works perfectly for me. Not well-documented? Hell, it’s a deep, dark secret! I have no idea why Nikon isn’t a little more free with information about their products. Well, you could still use an optometrist’s diopter lens to test with; find the one that works and subtract 1.0 from the lens value. N’ece se pas? Thanks for an extremely important piece of information, for me at least. Would you be familiar with Canon’s setup? For Canon viewfinders, a -0.5 diopter works for me. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

Had the same problem.so went to auto focus camara.Cannon EOS.was a little unsure in the beggining(being a pro) but ut was the best thing I ever did in photography. try it.

Response:

- Hide quoted text — Show quoted text – I know from recent experience that Nikon viewfinders are optically closer than inifinity because I am nearsighted and have vision corrected to better than 20/20 but as I have aged, the image is not sharp unless I supplement my eyeglasses with a +.5 dioper eyepiece correction lens. Anyone over 40 who thinks the image is less sharp than it should be, ought to try a +.5 or +.1 diopter and see if it helps. Nikon viewfinders are optically set to -1.0 diopters. According to this, you should be able to figure the diopter strength you need by taking this value and adding it to your eyeglasses diopter strength. For example, if your eyeglasses are +2.5 diopters (far vision), the resultant diopter strength figures to be a plus 1.5 diopter lens. Unfortunately, it doesn’t seem to work this way in real life. My eyeglasses have a +2.5 diopter lens and I need a +0.5 diopter lens to make the viewfinder image sharp. My best advice to determine what diopter strength is really needed is to go to a camera store that stocks all strengths and just try them, one at a time, until the correct one is found. This is not easy to do, since very few even well-stocked camera stores carry all strengths and sizes of diopter adjusting lenses. Second best advice, go to your optometrist and ask to try looking thru your viewfinder with different diopter lenses held between your eye and the viewfinder, thus determing the strength needed for the viewfinder; then order it thru the camera store. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass. Oh? I didn’t realize that. What would make an optician’s +1 diopter lens different than anyone else’s +1 diopter lens? This is not a belligerent question, but I am curious as to why you would say that. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Chuck, an optician’s +1 diopter is as marked, a lens of 1 meter focal length. A Nikon +1 diopter is not. Nikon marks its corrective eyepiece to show the resultant dipoter power, after taking into account that the optical path started with a -1 diopter correction. Thus a Nikon eyepiece marked +1 is not the same as a +1 diopter. It is a +2 diopter which when screwed into the viewfinder, nets out to +1 (-1 +2 = +1). Unfortunately, Nikon’s marking method is not well documented in their manuals (at least for the earlier manual cameras) and causes a lot of confusion and wasted money as people try to buy corrective eyepieces. This is explained in Carl Shipman’s 1986 book "How to Select & use Nikon SLR cameras" page 62. Hope this helps. TRUTH IN POSTING STATEMENT. Warning, the person responding to your post has never made a dime in the photography business and is therefore NOT CONSIDERED A PRO; with all the due rights, respect, and priviledges such an apellation is entitled thereof. Use the advice given with EXTREME CAUTION. All postings such as this should be considered a waste of time by the phtographic professionals that may lurk in these newsgroups. — Use address below for Email replies. Address on Header is bogus to defeat AutoSPAM. Rudy Garcia The answers I have found have just served to raise a whole new set of questions. In some ways I am as confused as ever, but I believe I am confused on a much higher level and about more important things. Author unknown

Response:

This is a good idea, too. However, I note that there is actually no perfect diopter strength, at least for my eyes. It would appear that somewhere between "0" and "+0.5" lies the correct lens for my eyes. Before someone chirps in with, "Are you SERIOUS?? That little bit of difference would make a difference??", the answer is, yes, absolutely. Especially with older eyes that can’t seem to compensate very much. Naturally, Nikon doesn’t make a diopter with a value of +0.25. – Hide quoted text — Show quoted text – The corrections lenses are hard to find — I had to order from B&H as usual. But another way to determine what diopter is right for you might be to find a camera shop that stocks the F5 or F100 with built-in adjustable eyepiece correction , much easier to find than the eyepiece lenses. Use the adjustable eyepiece as a test device, note the setting for sharpest image, and order that lens. I did not think of this technique before I bought mine, but the optician lens blank technique worked for me. I know from recent experience that Nikon viewfinders are optically closer than inifinity because I am nearsighted and have vision corrected to better than 20/20 but as I have aged, the image is not sharp unless I supplement my eyeglasses with a +.5 dioper eyepiece correction lens. Anyone over 40 who thinks the image is less sharp than it should be, ought to try a +.5 or +.1 diopter and see if it helps. Nikon viewfinders are optically set to -1.0 diopters. According to this, you should be able to figure the diopter strength you need by taking this value and adding it to your eyeglasses diopter strength. For example, if your eyeglasses are +2.5 diopters (far vision), the resultant diopter strength figures to be a plus 1.5 diopter lens. Unfortunately, it doesn’t seem to work this way in real life. My eyeglasses have a +2.5 diopter lens and I need a +0.5 diopter lens to make the viewfinder image sharp. My best advice to determine what diopter strength is really needed is to go to a camera store that stocks all strengths and just try them, one at a time, until the correct one is found. This is not easy to do, since very few even well-stocked camera stores carry all strengths and sizes of diopter adjusting lenses. Second best advice, go to your optometrist and ask to try looking thru your viewfinder with different diopter lenses held between your eye and the viewfinder, thus determing the strength needed for the viewfinder; then order it thru the camera store. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass. Oh? I didn’t realize that. What would make an optician’s +1 diopter lens different than anyone else’s +1 diopter lens? This is not a belligerent question, but I am curious as to why you would say that. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

– http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

The corrections lenses are hard to find — I had to order from B&H as usual. But another way to determine what diopter is right for you might be to find a camera shop that stocks the F5 or F100 with built-in adjustable eyepiece correction , much easier to find than the eyepiece lenses. Use the adjustable eyepiece as a test device, note the setting for sharpest image, and order that lens. I did not think of this technique before I bought mine, but the optician lens blank technique worked for me. – Hide quoted text — Show quoted text – I know from recent experience that Nikon viewfinders are optically closer than inifinity because I am nearsighted and have vision corrected to better than 20/20 but as I have aged, the image is not sharp unless I supplement my eyeglasses with a +.5 dioper eyepiece correction lens. Anyone over 40 who thinks the image is less sharp than it should be, ought to try a +.5 or +.1 diopter and see if it helps. Nikon viewfinders are optically set to -1.0 diopters. According to this, you should be able to figure the diopter strength you need by taking this value and adding it to your eyeglasses diopter strength. For example, if your eyeglasses are +2.5 diopters (far vision), the resultant diopter strength figures to be a plus 1.5 diopter lens. Unfortunately, it doesn’t seem to work this way in real life. My eyeglasses have a +2.5 diopter lens and I need a +0.5 diopter lens to make the viewfinder image sharp. My best advice to determine what diopter strength is really needed is to go to a camera store that stocks all strengths and just try them, one at a time, until the correct one is found. This is not easy to do, since very few even well-stocked camera stores carry all strengths and sizes of diopter adjusting lenses. Second best advice, go to your optometrist and ask to try looking thru your viewfinder with different diopter lenses held between your eye and the viewfinder, thus determing the strength needed for the viewfinder; then order it thru the camera store. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass. Oh? I didn’t realize that. What would make an optician’s +1 diopter lens different than anyone else’s +1 diopter lens? This is not a belligerent question, but I am curious as to why you would say that. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

– Hide quoted text — Show quoted text – I know from recent experience that Nikon viewfinders are optically closer than inifinity because I am nearsighted and have vision corrected to better than 20/20 but as I have aged, the image is not sharp unless I supplement my eyeglasses with a +.5 dioper eyepiece correction lens. Anyone over 40 who thinks the image is less sharp than it should be, ought to try a +.5 or +.1 diopter and see if it helps. Nikon viewfinders are optically set to -1.0 diopters. According to this, you should be able to figure the diopter strength you need by taking this value and adding it to your eyeglasses diopter strength. For example, if your eyeglasses are +2.5 diopters (far vision), the resultant diopter strength figures to be a plus 1.5 diopter lens. Unfortunately, it doesn’t seem to work this way in real life. My eyeglasses have a +2.5 diopter lens and I need a +0.5 diopter lens to make the viewfinder image sharp. My best advice to determine what diopter strength is really needed is to go to a camera store that stocks all strengths and just try them, one at a time, until the correct one is found. This is not easy to do, since very few even well-stocked camera stores carry all strengths and sizes of diopter adjusting lenses. Second best advice, go to your optometrist and ask to try looking thru your viewfinder with different diopter lenses held between your eye and the viewfinder, thus determing the strength needed for the viewfinder; then order it thru the camera store. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass.

Oh? I didn’t realize that. What would make an optician’s +1 diopter lens different than anyone else’s +1 diopter lens? This is not a belligerent question, but I am curious as to why you would say that. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

Unfortunately the Nikon diopters factor in the fact (as you rightly explained) that the optical system is set for -1 diopter. This causes a problem with your last sugestion. Namely, a Nikon +1 diopter, for example, is not the same as an optician’s +1 diopter glass. — Use address below for Email replies. Address on Header is bogus to defeat AutoSPAM. Rudy Garcia The answers I have found have just served to raise a whole new set of questions. In some ways I am as confused as ever, but I believe I am confused on a much higher level and about more important things. Author unknown

Response:

Nikon viewfinders are optically set to -1.0 diopters. According to this, you should be able to figure the diopter strength you need by taking this value and adding it to your eyeglasses diopter strength. For example, if your eyeglasses are +2.5 diopters (far vision), the resultant diopter strength figures to be a plus 1.5 diopter lens. Unfortunately, it doesn’t seem to work this way in real life. My eyeglasses have a +2.5 diopter lens and I need a +0.5 diopter lens to make the viewfinder image sharp. My best advice to determine what diopter strength is really needed is to go to a camera store that stocks all strengths and just try them, one at a time, until the correct one is found. This is not easy to do, since very few even well-stocked camera stores carry all strengths and sizes of diopter adjusting lenses. Second best advice, go to your optometrist and ask to try looking thru your viewfinder with different diopter lenses held between your eye and the viewfinder, thus determing the strength needed for the viewfinder; then order it thru the camera store. — http://www.enteract.com/~ckross/ Digital and Film-Based Photography

Response:

I know from recent experience that Nikon viewfinders are optically closer than inifinity because I am nearsighted and have vision corrected to better than 20/20 but as I have aged, the image is not sharp unless I supplement my eyeglasses with a +.5 dioper eyepiece correction lens. Anyone over 40 who thinks the image is less sharp than it should be, ought to try a +.5 or +.1 diopter and see if it helps. – Hide quoted text — Show quoted text – Hi, My understanding is that most SLR viewfinder systems are calibrated to be seen at infinity focus. If your eyesight cannot see at infinity unaided (such as mine, I am myopic – near-sighted), you will not be able to get a true focus on the film EVEN if the image appears in focus in the viewfinder. If this is your condition either wear your prescription glasses or use, as someone else suggested, a diopter lens appropriate to your eyesight. If, however, you are hyperopic (far-sighted), where you do NOT need glasses to see far (such as to drive a car), then you may be able to use the viewfinder unaided and get the focus on film as you see on the finder. HTH, Dirk Bakker Hi all, This might sound like a stupid question (and perhaps it is) but i’ll ask anyway. My eyesight is not too far below the 20/20 standard and I would like to know if, when my eye sees an image as being in focus (as indicated by the split image / pixelate type viewfinder), is it actually out of focus (with my eyesight not being 20/20. I do not use a correcting view piece. Hope you can help.

Response:

Hi, My understanding is that most SLR viewfinder systems are calibrated to be seen at infinity focus. If your eyesight cannot see at infinity unaided (such as mine, I am myopic – near-sighted), you will not be able to get a true focus on the film EVEN if the image appears in focus in the viewfinder. If this is your condition either wear your prescription glasses or use, as someone else suggested, a diopter lens appropriate to your eyesight. If, however, you are hyperopic (far-sighted), where you do NOT need glasses to see far (such as to drive a car), then you may be able to use the viewfinder unaided and get the focus on film as you see on the finder. HTH, Dirk Bakker – Hide quoted text — Show quoted text – Hi all, This might sound like a stupid question (and perhaps it is) but i’ll ask anyway. My eyesight is not too far below the 20/20 standard and I would like to know if, when my eye sees an image as being in focus (as indicated by the split image / pixelate type viewfinder), is it actually out of focus (with my eyesight not being 20/20. I do not use a correcting view piece. Hope you can help.

Response:

As one who has had eyes go bad. If your eyes can focus on any marking in the viewfinder you are OK. If not, nothing will appear in focus on the ground glass, even when properly focused. Even then you can focus properly, by going for the best you can see, but is very slow process. Focusing with the split image should always be correct, unless your eysight is so bad that it looks fuzzy to you. Hi all, This might sound like a stupid question (and perhaps it is) but i’ll ask anyway. My eyesight is not too far below the 20/20 standard and I would like to know if, when my eye sees an image as being in focus (as indicated by the split image / pixelate type viewfinder), is it actually out of focus (with my eyesight not being 20/20. I do not use a correcting view piece. Hope you can help.

- – * For God so loved the world that He gave his only begotten Son, * * that whoever believes in Him should not perish… John 3:16 * * W. Paul Mills * Topeka, Kansas, U.S.A. * * Bill, I was there several years ago, why would I want to go back? *

Response:

The actual distance of the viewfinder image is usually not specified and probably varies from camera brand to brand. I found through trial and error that a +.5 was what I needed for my Nikon 90s and also for my FE-2, so at least with Nikon, perhaps it is a set distance. The F5 and F100 have built in adjustment which is ideal. The problem is that your eyeglasses will correct for distance of twenty feet and beyond, and if you have bifocals you will have correction for reading distance, but the viewfinder image is in between, and as you age your eyes may not be able to focus enough to get a sharp viewfinder image. This is where AF really helps, but it is still nice to see what you are photographing. If you do not have a shop nearby that carries the eyepiece correction lenses, you can experiment by checking with a camera that has the correction adjustment or you can visit your optician and borrow a +.5 and +1 lens blank to hold in front of your viewfinder to see if it improves the image for you.

– Hide quoted text — Show quoted text -20/20 vision is not necessary for properly focusing an SLR with a split-image focusing aid on the focus screen. What is important is that you are able to focus on the screen itself. In most SLRs, the focusing screen appears to be 1 meter away which is a difficult distance for critical focus, especially for older users. The simplest solution is to attach a plus 1 diopter to your viewfinder which will make the screen appear to be at infinity. This is a more comfortable distance to focus on than 1 meter. Some manufacturers offer a range of plus diopters for their cameras so that you can pick the one that works best for you.

Response:

From what I was told by my optician, if you don’t have 20/20 vision, what you actually see as "in focus" is a range rather than a point. Anywhere in this range is perceived as "in focus" and may or may not be the true focus point.

My guess is that as long as you can see the split image/micro-prism collar clearly (including the two halves of the image) you can focus correctly, focussing via the ground glass surrounding it might be different. — John Preston, Lancs, UK.

Response:

20/20 vision is not necessary for properly focusing an SLR with a split-image focusing aid on the focus screen. What is important is that you are able to focus on the screen itself. In most SLRs, the focusing screen appears to be 1 meter away which is a difficult distance for critical focus, especially for older users. The simplest solution is to attach a plus 1 diopter to your viewfinder which will make the screen appear to be at infinity. This is a more comfortable distance to focus on than 1 meter. Some manufacturers offer a range of plus diopters for their cameras so that you can pick the one that works best for you.

Response:

Hi all, This might sound like a stupid question (and perhaps it is) but i’ll ask anyway. My eyesight is not too far below the 20/20 standard and I would like to know if, when my eye sees an image as being in focus (as indicated by the split image / pixelate type viewfinder), is it actually out of focus (with my eyesight not being 20/20. I do not use a correcting view piece. Hope you can help.

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