Just my two bobs worth on this issue after about sixty years of experience with
these issues and 35 mm cameras.
Good reflex viewfinders are expensive to make and are no longer made but as a
rule of thumb, the better (dearer) the camera the better will be the viewfinder.
The last viewfinder that I am aware of that had a proper spiral focusing
eyepiece that showed you the full frame was the Leitz Visoflex II reflex
attachment for Leica M cameras. That was probably about 50 years ago and the
diopter adjustment ( which allows for how long or short-sighted you are) would
have been in the order of minus two to plus two. This is sufficient for most
westerners. If you need more than this you need to attach an accessory dioptre
adjusting lens to the outside, or wear glasses.
Oriental eyes are different, they tend to be short sighted and this is
reflected in the cameras they make - the modern viewfinders have less
adjustment and tend towards the negative. In addition, in my experience the
quality of the optics in modern viewfinders is very basic, often the viewing
lens is a simple plano-convex element which is cheap to make.
A good quality viewfinder should have the following characteristics.
1. What you see is what you get i.e. it should show you 100% of the field (your
picture). Cheap viewfinders usually only show about 90% and crop the rest off.
2. Should show you a large picture (easier to see) up towards 1x. The
professional cameras like the Canon 1D series or the Nikon D5 have the best
viewfinders. That's one of the reasons they cost more.
3. They should have a wide dioptre adjustment. This is best achieved by a
spiral focusing lens, very rare these days if they even exist. The systems I am
aware of (small sliding or rotating knobs) belong in the toy class and have a
relatively small adjustment, sometimes only up to +1. Unfortunately this is the
case now even with professional cameras.
4. Better viewfinders have a long eyepoint. This is the point where your eye
can focus and still see the full frame of view. Long eyepoints are more
expensive to achieve, but allow the viewer to wear glasses. Usually when
wearing glasses you won't see the full frame of view.
If you have to wear glasses and are not sure whether your subject is exactly in
focus, my advice is use autofocus and trust it. For many years I stuck with
manual focus but when I finally decided to go with autofocus it was a
revelation. Mind you if you are super critical, autofocus does have an order of
accuracy. Often if you take several exposures one after the other, one will be
in sharper focus than the others.
I have just invested in a Nikon D500, a camera that has been DESIGNED for
wildlife photography - the autofocus is absolutely amazing. So far I have found
only one negative. Whilst the viewfinder is large and accurate it still has a
"toy" focusing system ( -2 to +1 ) and a short eyepoint. I notice from
looking up the Canon 1DS camera the dioptre adjustment built in is from -3 to
+1 , not enough for many westerners, however by and large Canon viewfinders
have a longer eyepoint than Nikon.
For an excellent article on this subject have a look at
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