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Author Topic: OVF's for people who need reading glasses  (Read 2148 times)
NigelC
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« on: March 20, 2013, 06:21:30 AM »
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Surely there must be people out there who need reading glasses who are using optical viewfinders?
I want to get the Sigma VF21 for the DP2, but there is no dioptre adjustment - does this mean I have to use it with my reading glasses on? - this takes away one of what I thought would be the advantages.
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SangRaal
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« Reply #1 on: March 21, 2013, 11:08:14 AM »
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I really don't get what you want to accomplish? Reading glasses are for close up you can't use an optical viewfinder for close up on the sigmaDP cameras (nor any similar camera) because of framing parallax errors. Only at mid range and longer can you use an optical viewfinder. You might want to check some of the other brands of OVF's before you buy the sigma (voigtlander is well made and should be less expensive).
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NigelC
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« Reply #2 on: March 21, 2013, 12:16:50 PM »
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I really don't get what you want to accomplish? Reading glasses are for close up you can't use an optical viewfinder for close up on the sigmaDP cameras (nor any similar camera) because of framing parallax errors. Only at mid range and longer can you use an optical viewfinder. You might want to check some of the other brands of OVF's before you buy the sigma (voigtlander is well made and should be less expensive).

You obviously haven't reached the stage in your life were you need to deal with this! The distance from the camera to the subject is irrelevant - it's the focus point of the viewfinder. If there is no dioptric adjustment it is fixed - normally an optical (or an EVF for that matter) viewfinder will have a small range of dioptric adjustment to accommodate differences in individuals sight. For example, with my 5D or GH2 if I turn the dipotric adjustment to the wrong setting for my eyes everything, at any subject distance form the camera, appears slightly unsharp. Wearing my reading glasses is unsatisfactory because it affects the framing. My sight is such that I cannot focus unassisted now on anything under a metre away.

BTW in the UK the Voigtlander is no chepare than the Sigma which I've ordered anyway - I'll have to send it back if it doesn't work
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Greg D
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« Reply #3 on: March 21, 2013, 12:45:22 PM »
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I've been a bifocal wearer for about 10 years, and trifocal for the last two.  I might be misunderstanding the problem here, but I think that it is in fact the camera-to-subject distance that matters.  For reasons (physical, psychological or both) unknown to me, it is not the viewfinder image an inch or so away that your eye focuses on (or at least that your eye "thinks" it focuses on).  My eyes certainly can't do that.  You can demonstrate this by placing an object a meter or so away from a mirror, then focusing on the image in the mirror.  You will find that you can focus on the mirror image from just inches away, though you couldn't possibly focus that close on the object itself.  I don't know why this is, but it's clearly the case.  If you're trying to use your VF with reading glasses that may be the source of the problem.  Try it with whatever glasses you use, if any, for distance vision.  Again, excuse me (and clarify) if I'm misconstruing the problem.....
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Colorado David
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« Reply #4 on: March 21, 2013, 12:55:31 PM »
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People with presbyopia do need a diopter adjustment to get the most out of an optical viewfinder.  Just for fun, take your diopter equipped DSLR and rack the diopter adjustment all the way one way or the other and look for yourself.
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rgs
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« Reply #5 on: March 21, 2013, 01:17:28 PM »
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I am extremely near sighted for which I wear contacts. I am also old enough to need reading glasses but don't use them most of the time. I have what a monovision prescription for my contacts which means one is set for distance and one for close vision (in my case a medium distance good for reading music and computer screens). Still, if I need really good vision up close, I use some weak reading glasses. The viewfinders on my cameras also have the diopter adjustment I need to see up close.

I don't know the optics involved well and the mirror example seems to make sense. Yet I know that if I use an uncorrected viewfinder, I can't see well enough. The OP is right. If you need reading glasses, you need a correction in your viewfinder.
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AFairley
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« Reply #6 on: March 21, 2013, 01:55:14 PM »
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For a SLR/DSLR, the apparent viewing distance of the screen is usually in the 1 to 3 meter range, so anyone who is either near- or far-sighted enough will need diopter correction.  But I don't know what the story is with see-through OVFs.  The OP might be able to get a diopter lens for a DSLR and figure out a way to attach it to the eyepiece of the VF, but I expect picking the strength would be trial and error.  BTW, the way the manfacturer's diopter lenses can be misleading.  For example a Nikon lens marked +2 is not +2 strength, rather, it will give a total +2 correction when combined with the camera optics at the default setting (which is not 0, but I don't remember what it is).
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NigelC
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« Reply #7 on: March 21, 2013, 03:22:17 PM »
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For a SLR/DSLR, the apparent viewing distance of the screen is usually in the 1 to 3 meter range, so anyone who is either near- or far-sighted enough will need diopter correction.  But I don't know what the story is with see-through OVFs.  The OP might be able to get a diopter lens for a DSLR and figure out a way to attach it to the eyepiece of the VF, but I expect picking the strength would be trial and error.  BTW, the way the manfacturer's diopter lenses can be misleading.  For example a Nikon lens marked +2 is not +2 strength, rather, it will give a total +2 correction when combined with the camera optics at the default setting (which is not 0, but I don't remember what it is).

Thank you finally someone who gets it! The camera to subject distance is irrelevant - its the apparent viewing distance of the screen which determines how much correction is needed.This can be easily demonstarted by someone who has perfect vision - set the dioptre adjustment to its extreme and the image through the viewfinder will have the same degree of "unfocus" whether the camera is focussed on close objects or infinity. You put your finger on the my real question (obviously badly phrased) which is do external V/F s behave the same way as the reflex viewfinder on a DSLR?
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AFairley
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« Reply #8 on: March 21, 2013, 03:48:12 PM »
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You put your finger on the my real question (obviously badly phrased) which is do external V/F s behave the same way as the reflex viewfinder on a DSLR?

My reading indicates that the image you see with a "see-through" VF is an aerial image, which therefore has an apparent distance, but I don't know what that distance is. 
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maxgruzen
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« Reply #9 on: March 21, 2013, 04:05:12 PM »
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maxgruzen
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Re: Sigma DP2 Merrill Experiences
Reply #855 on: March 20, 2013, 04:16:08 PM
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Lainer, I use a DP2M with the Vf21. I need glasses to read,-250 to 275, and have no problem with the viewfinder. The viewfinder is so small I don't even know its there but it's great in bright sun. The Voitlander finder is a better optic, but is a bit bigger. My 2 cents on the L bracket and grip is this....I love the merrill because it is small and light, so why put a big heavy RRS bracket and grip on it. Richard Feneric makes a grip that is small ,light and works great. I walk around all day with the Merrill just hanging on my finger, and even with bad arthritis I don't even feel it. I have his grip on all my cameras. For an L bracket I use the fabulous JTEC bracket. Again small and light. Just some other options for you to Google and check out......Max
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theguywitha645d
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« Reply #10 on: March 21, 2013, 04:55:07 PM »
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These are Galilean finders. They project a virtual image, not a real image of a DSLR. Diopters are really not needed--I have reading glasses and no problem using add-on OVFs.
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NigelC
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« Reply #11 on: March 22, 2013, 03:32:19 AM »
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These are Galilean finders. They project a virtual image, not a real image of a DSLR. Diopters are really not needed--I have reading glasses and no problem using add-on OVFs.

Thank you - I'm hoping it will come in the post today so we'll see how it works for me.
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