Eye glasses and manual focusing

[tkamiya]

I wonder if I'm seeing things or if this is really the way it is....

I have been having problems with manual focusing. It's not that it's impossible but it's harder. I don't see the images in view finder as crisply as I'd like making the split prism image more difficult to match exactly.

I wear bi-focal eye glasses. I have several. I also have single vision eye glasses. They are made to the same power. (the distance part anyway)

It seems single vision glasses offer more crisp view of the view finder, and more importantly, the split prism part. I can focus little easier than when I'm using bi-focals.

Do others have the similar experience?

I'm thinking, since bi-focal are two lens with varying focal length in one, and mine is progressive, which makes the transition part continuously variable. Wouldn't it make this glass more less have aberration characteristic where not all rays focus at the same point?

Anyone else notice this?

 

[Sirius Glass]

Contact lenses work well except when I am working with the LF ground glass. Then I slip on much stronger than usual reading glasses.

 

[tkamiya]

Really? Contact lens actually have softer image than glasses. My optometrist have been telling me this and I can confirm it too. My problem isn't the magnification of the images. It's really an issue with crispness, sharpness, and clear edge contrast.

 

[Bob-D659]

Ok, I have bifocals, old style lined ones. To see the viewfinder clearly, I made a +1.25 diopter lens from a pair of dollar store reading glasses and put the lens in a normal diopter lens carrier. Did this for both the F3 and the F's and Nikkormats. Works like a charm.

I just stood 1 meter away from the glasses stand and looked thru various reading glasses while wearing my regular ones to see what power was needed for a nice sharp view of the test block of text on the stand.


Most distance parts of bifocals are not set for infinity, but a much closer distance.

 

[Neanderman]

For MF, I have to focus using the built-in magnifier; for LF, I use reading glasses. It's 35mm that I don't have a good solution for. I'd buy some diopters, but they don't make them for my cameras anymore and they are pretty much impossible to find used. :-(

Ed

 

[Sirius Glass]

I see much better with my soft contact lenses that my bifocals or trifocals; distance, contrast, crispness, sharpness ... With the right reading glasses, reading is no problem. With 35mm and MF I do not need reading glasses. I do not need reading glasses with the Graflex [SLR] and the Speed Graphic. I only need strong magnifiers for the critical focus with the Speed Graphic when I am using the ground glass for focusing and shifts, raises and tilts.

Steve

 

[tkamiya]

Steve,
Do you have no-line progressive or lined ones?

 

[Sirius Glass]

Steve,
Do you have no-line progressive or lined ones?

Both. I prefer the progressives but I do not have a problem using lined glasses.

 

[Pgeobc]

Well, just having gone through this same problem, I will attempt to give you an answer. After age 40, or so, the lens of your eye loses its elasticity and, therefore, loses its ability to focus closely. That is called "Old-age Farsightedness" or Presbyopia. There is no way to tell just how farsighted one will end up, but it may be a while before it settles down to the final stage.

Camera manufacturers usually build SLR viewers with an apparent distance of 1 meter. That works fine for normal eyes that can adjust, but works poorly for eyes that are farsighted and cannot adjust/acomodate.

If you are not too farsighted, you can sometimes get cameras with adjustable dioptric correction in the viewfinder. If you are further out, or your camera is not adjustable, you can get add-on viewfinder diopters.

Another way is to go down to the Five-and-Dime or bargain store, or drugstore and buy a cheap pair of reading glasses. Take your camer with you and keep trying different corrections until you like the picture and can focus correctly. I needed to use about a +2.50 for an SLR and about a +1.50 for my Hasselblad waist-level finder. Your numbers may very well differ, but the correction will always be +, unless you are nearsighted. In addition, bifocals and continuous-change glasses suck, in my opinion.

My real break came when I had to have cataract surgery. At that time, one is expected to state how they want the final view to look. Since I had been extremely nearsighted, they offered to let me return to that since I had been so for so many years --or-- they offered to correct my vision for normal distance visions, for which I would wear reading glasses for close work. I elected to be farsighted; they installed the lenses, and I ended up very slightly closer than that. I am about 1 Diopter nearsighted and that works well on SLRs and I can use +1.50 reading glasses for my waist-level viewfinders.

My optometrist was very good in helping me find the right correction for my cameras when I went there. I dragged my cameras with me to the eye exam and explained what I wanted. She understoon perfectly and, in short order, had me happy.

 

[tkamiya]

Geo,

Thank you very much for your detailed response. Much appreciated. My problem is little different. I'm near sighted but recently, I acquired some far sightedness. The latter part isn't that bad yet. With diopter corrections I can bring the view finder in focus, as well as those little indicators in the view finder. I can also bring the split prism in focus.

The real problem starts after that. Although those things in view finders are in focus, they lack clearly defined edges. When I bring two parts of split prism together to get it to focus, rather than looking like two crisp images matching, they look like two Twinkies coming together. (well, not nearly that bad, but I hope you get the idea...) Edges are soft - fuzzy - not-clearly-defined.... which makes it difficult to attain exact focus.

I was thinking for a while, and I thought - well - this looks like soft focus lens! So I started to think some more. Someone explained to me how soft focus lens actually work. Not all rays come together at a point. Well, that's exactly what bi-focal glasses do, and mine is progressive.

Then, I switched my glasses to a single focal one. It's a little better....

I was wondering if others experience the same.

 

[Bill Burk]

Hi tkamiya,

I'm a die-hard glass-only bi-focal only guy. I see something like what you describe on my OM-4. But I picked up a clean Nikon FG the other day at a charity sale and, wow, that viewfinder is clear and crisp the way a camera should be. The old Pentax is dark but still the viewfinder is crisp and focuses well.

Now I'm convinced the problem is that the OM-4 is overdue for CLA.

I've got another camera that I have to use the lower-bifocal on to see clearly. I think the problem in some cases might be different cameras have different virtual viewfinder focus distances.

 

[tkamiya]

Maybe I need a new set of eyeballs... I have this problem with every camera I own. Some of them are only few years old. I do agree, some view finders are nice and bright - which makes it quite a bit easier. I have a Mamiya M645Pro that I'm having awful problems with....

 

[ic-racer]

I usually forgo the glasses and use the appropriate diopter correction on the viewfinder eyepiece.

 

[DBP]

When I finally got bifocals, the advice from everyone here was to get the lined kind, which have worked fine. For closeup viewfinders I use the top and for waist level the bottom (and the magnifier). I often take the glasses off for large format, or at least slide them down and look over them. The only real problem has been the angled finder on my Kiev 88, which lines up with the reading lens. I have to keep reminding myself to tilt my head more.

 

[Diapositivo]

With cameras that have built-in diopter corrections, and in general when making test with corrective lenses, it is important to do every test for a fraction of a second. If you try to look inside your viewfinder and slowly turn the diopter correction until the vision is "just perfect" your eyes, during the operation, will compensate and strain. You'll find a setting which always forces your eye to compensate and strain (and one day your eye will not compensate any more that well).

The right strategy is to choose a certain compensation, let the eye rest for some seconds, look inside the viewfinder for a fraction of a second and see in a glimpse how it is. If it isn't satisfactory, stop looking inside the viewfinder, turn the dial a little, and again do have a glimpse of how it works. Evaluation must be made by immediate sensation, before the eye has the time to adapt.

Bill, the reason why your Nikon FG appears to be clearer than your Olympus OM-4 might be that the Olympus OM-4, which has IIRC a diopter correction, is not correctly set for your eyes.

 

[Paul Goutiere]

I usually forgo the glasses and use the appropriate diopter correction on the viewfinder eyepiece.

I do the same thing. I'm nearsighted.

All my cameras; Hasselblad, Nikons and Leica Ms have -2 diopters fitted.

I wear my eyeglasses on a cord that I can hang around my neck.

 

[Sirius Glass]

Maybe I need a new set of eyeballs... I have this problem with every camera I own. Some of them are only few years old. I do agree, some view finders are nice and bright - which makes it quite a bit easier. I have a Mamiya M645Pro that I'm having awful problems with....

Screw getting piece part replacements! Each time you have to go through recovery and then rehabilitation!


I am going for a full body replacement with an 18 to 21 male hard body! Only one recovery and only one rehabilitation! :w00t:

 

[jeffreyg]

Ditto for the diopter correction for the viewfinder eyepiece. You might add a removable rubber eyecup to block extraneous light.

http://www.jeffreyglasser.com/

 

[Bill Burk]

Bill, the reason why your Nikon FG appears to be clearer than your Olympus OM-4 might be that the Olympus OM-4, which has IIRC a diopter correction, is not correctly set for your eyes.

OM-4 does have diopter correction, and I will try your advice ... after I get the CLA done.

But it really is dirty on three surfaces. But wait, it gets worse. The diopter lens is out of its bracket! So I'm lucky I can see through it at all.

On viewfinder brightness, OM-4 sends some light through the semi-silver meter path. The SEI photometer tells me I lose two stops of light through the OM-4 viewfinder but I lose only one stop of light through the FG [and OM-1].

So as much as a stop may be going through the semi-silver path of the OM-4. Some of my measured light loss is due to dust.

 

[Bill Burk]

I am going for a full body replacement with an 18 to 21 male hard body! Only one recovery and only one rehabilitation! :w00t:

Ha, it's called having kids.

You have to buy cameras for all these replacement bodies.

But there is some good news. My replacements don't need glasses!

 

[Chan Tran]

You just need a single focal eyeglass that is optimized for 1m viewing distance than it would work fine with just about any camera. Progressive works but only for a very small portion of the glass that is right for the 1m distance. Your single focal is a little better but may be optimized for reading distance which is nearer than the 1m. I asked my optometrist but he didn't give me answer. You have problem even when using the spit image then your viewing is very poor. You should have a crisp enough image to focus without the split image.

 

[Pgeobc]

"I'm near sighted but recently, I acquired some far sightedness."

That was my problem, too. Initially, I started using an SLR with progressive lenses. Well, that just didn't cut it. Unless I let my F100 autofocus, my pics would always be near misses. Next try was to use a waist-level finder in my Hasselblad with the progressives and that was a wash, too. I did make a little progress by getting a screen for the Hasselblad that had a split-image, but they are not the answer to everything, either. Then my wife and I went to the "Dollar" store and tried cheap reading glasses and that was when I got the first real break. Cheap reading glasses can be used with a glasses tether so that they can be off and on and are, that way, more convenient. Even if you are nearsighted, this can work because the beauty of diopter measurement is that is is just plain additive or subtractive.

What I did not realize was that the far-sightedness had put an overlay onto my nearsightedness--again, by subtracting--and changed my correction and that the distances involved with viewfinders were not covered correctly with the progressive lenses. In addition, the progressive lenses only have a small area through which you can look to get any specific correction and it is easy to get it wrong.

I started using a prism finder on my Hasselblad and paid big money for add-on diopters and found, sure enuff, that if I figured a decrease from the standard +6.50D that it took to correct my nearsightedness and used, say a +4.00D lens, then the prism finder looked and worked well. The difference is the number of diopters that my lens had gone toward farsightedness. It was an expensive tinkering project that could have been done more easily with the help of my optometrist.

If you have a good optometrist friend, say one to whom you have gone for a number of years, ask to borrow their set of "try lenses." Every optometrist on the planet is trained using them and will, somewhere, have a set. You can then go home, and try the various corrections with your cameras, taking care to note the numbers, and see just what you need.

About the "Twinkie" problem: I really do not think that you are having any more problem than simply not getting the correction really right. The advice about looking only for a short time, looking away, and looking back is good advice and I use that often in focusing rifle scopes, too. Some of these focusing screens nowadays, especially the ones that are very bright, have a rather indistinct area of sharp focus, too. I noticed that when I bought a Beattie Intenscreen for my 4x5 and had no end of trouble getting really good, tight focus.

Hope that helps.