SLR Viewfinder Vision Corrected Vs Diopter

[walter g]

Hopefully this is a simple question. I need glasses to read. In US measurements, my glasses are +1.25.

Looking up the specs on my Canon AT-1, it is listed as .82X veiwfinder.
My Minolta X-370 is listed as .9X. My Yashica Electro X dosen't list a value in the specs. Possibly noncorrected.

So am I understanding the terms correctly. Because of the built in correction in both the Canon and Minolta, I don;t need a diopter.

Is there any way to check to see if the Yashica is corrected?
Is the values I listed above a correction value, or do they mean something else?

This is the first year I've had to wear glasses of any sort, so this is a new problem for me.

[Orio]

reading glasses value does not really apply for photography unless you do macro at closeup distance.
If you are shooting a landscape, or even just if you are shooting a model at a typical portrait distance of 3-4 meters, it is not the reading correction that you need to apply, but the long distance correction, which is the correction you would have on eyeglasses for driving a car - if you need any.

[visualopsins]

Got some close-up attachment lenses, eh?

[walter g]

I've read more on the net sense I posted this.Pretty confusing.
But here is what I got out of it.

If you use reading glasses you need + diopters. If you need glasses for distance you need - diopters.
Camera viefinders have a built in correction, So you have to take this into consideration when you buy a viewfinder diopter.

1960's cameras have a ground glass viewfinder, if you needed correction you took it to an optritian to be reground.
So my Yashica has no correction.

By what I'm reading my Canon and Minolta have + correction. Why?

Some of the new cameras have - correction and also have adjustable diopters.

So your saying that + diopters will only help out under 3 feet?

[walter g]

I tried a basic test. Using the foot bord of my bed as a camera rest, and the headboard to hold a B&H catalog, I tried testing all 3 cameras.
I used a pillow to hold the catalog so distance was 5'10".

Printing was sharp on both the Canon and Minolta that have + correction,
and distance was correct on both lenses.
Yashica trying to get it sharp was more of a problem, and distance scale didn't match. Yashica no correction.

Now this was a quick test and I used 3 different lenses.
So this could be a lens problem. 135mm lenses were used for all 3 cameras.
By the way, my distance vision is perfect.

I will retry this test tommorow with a tripod, but each camera was in the exact same spot.
I will also use only one lens a Tmount and just change the adapter.
I will also test at different distances.To see if the result changes.

Any recomendations for other test variables?

[peterqd]

My eyes are similar to yours Walter. I don't have a big problem focussing and framing a subject, although a correction lens makes it easier. However I can't focus on the information in the viewfinder itself without one.

Did you see my thread about making a viewfinder correction lens from a pair of old reading glasses?

[walter g]

[trev]

If memory serves me correctly, most if not all, Canon manual focus cameras and indeed even auto focus film cameras have a -1 built in which needs to be taken into account when ordering diotric lenses. Obviously Canon and I suppose most digital slr's have adjustable diotric built into the viewfinders.

[magkelly]

Seems some of them do. It's one of the many reasons I won't be shooting film for long when I start doing a lot more paid work. I need that adjustable diopter bit.

I have always had problems with distance and I've always had a bit of astigmatism. Lately I'm also experiencing that loss of close vision thing that most people get when they're getting older but in my case it seems to be very inconsistent. My eyes can't seen to settle down at all. One day I can't see much of anything in terms of small print, the next I can and I don't need reading glasses to do it.

My eye doctor practically had a fit trying to correct for it. (He won't even consider contacts. He says it's useless. I'd never be able to get it to work long enough.) I finally coped by grabbing several pairs of drugstore reading glasses at different strengths. Which pair I use, if any, depends upon the day and what my eyes decide they want to do. I also have a standard pair of distance glasses and paired sunglasses that's just for driving.

Being able to adjust the camera to compensate sounds like a pretty good idea to me. It would probably save me a fortune every other year in eye glasses and eye glass anti-fog spray!

[peterqd]

When you're long-sighted you need to wear glasses to read the shutter speed/ASA/frame counter/aperture scale settings on an SLR and the LCD on a DSLR. So when a correction lens is fitted in the viewfinder, or when the dioptric adjuster is set, you have to take the glasses off to take the picture. You can't win!

[Orio]

Canon DSLR cameras have built in correction in the viewfinder for both - and +

The viewing matter is not always as simple as being short or long sighted.
For instance my right eye looks almost correctly in the distance but fails at reading distance. My left eye does exactly the opposite.
You of course use only one eye for focusing so this would appear simple, but some eyes do couple astigmatism, short sight and long sight to various degrees at various distances.
My eyesight is such and for this reason I needed to find (and pay) an excellent eye doctor to measure my sight carefully and that took more than two hours of all existing tests.

Basically you need to make a choice and set the camera for the most common use.
I for instance would not set viewfinder for infinity because lenses do stop at infinity on their own (you need to check accuracy of the lenses to infinity though)
Also I do rarely macro so I do not set for close distances either.
My viewfinder is corrected for aiming at a target of about 4-5 meters, which is the typical portrait distance and for me the most critical.

One way to cut it short would be to always focus with liveview, in which case of course you would only need your reading eyeglasses...

[fish4570]

all I know is this: my photos look far, far sharper since I began using my readers to focus; the images from my 400/6.3 suddenly became sharp when I wore my readers to focus.
I generally use +2. Distance vision is still stinking good for 59-yeaR-old eyes ...

[nemesis101]

I am now at the stage where I look like a nodding dog!

I have varifocal lenses in my specs.. and find that I need the top bit to see the scene, the middle bit to view through the lens and the bottom bit to see the picture on the LCD.. This results in my constantly moving my head up and down giving myself a headache! lol

I wish they could develop an auto-focus lens that adjusted itself to what I was looking at.. some kind of meniscus maybe manipulated by magnets like the old CRT screens were? lol

Doug

PS I got a bit confused by the x86% etc. that was being mentioned. That's the magnification (or reduction) of the image seen in the viewfinder compared with the image seen with the naked eye surely, and not connected with the dioptre adjustment that allows one to compensate for fault focusing of the eyes?

[Nesster]

I'm scratching my head as well... the viewfinder magnification doesn't have to do with diopters, it has to do with the size of the image vs. real life through a 50mm lens.

In old camera reviews I've seen mention of 'apparent viewing distance' as well - often the viewfinder indicators, e.g. match needles, aperture read outs etc, are at a different apparent distance than the focusing screen itself.

Like Doug says, the diopter is to aid the eye to focus on the screen and/or indicators, if they appear to be at a different distance.

The difference with the Canon, Minolta and Yashica focus-ability lies in some combination of: view finder contrast and 'snap', the apparent distance to the focus screen (ie. at what distance does your eye need to focus to see the image), viewfinder brightness, and a few other variables.

If your eye has difficulty in focusing to the screen you need a diopter.

The adjustable diopters as implemented in many dslr's are a pain, as they easily slide off adjustment, which is something you don't always notice immediately.

One reason they introduced microprisms and split prisms is to help with this overall problem. You may see the glimmer of the microprism disappear as you focus, while the view remains a bit fuzzy overall to your eye.

[walter g]

I was gone most of the day so I didn't get to retest with a single lens.

But the results came down to this. With the Minolta and Canon at 5'10"
I was able to read the text on the page and get focus whithin seconds. So
no vision diopter was needed.

With the Yashica the words were smaller and I was squinting trying to read the words. It took 3 to 4 times as long to get focus, and I'm not 100% sure I had it.

So I would need a vision diopter, with this camera.

[Nesster]

Yes, I would think that was correct. Easy way to test, try to focus using reading glasses.

[walter g]

It seemed okay with reading glasses, but I prefer to retest with one single lens to remove any variables.