Just Googled Optivisor - I think it exceeds my dork threshold. Bad enough to be using a view camera without looking like a Martian while you do it. I have some cheap, strong reading glasses I keep in the camera bag, and I do critical focusing with an old 7x Calumet loupe. Works fine, except for getting the lanyards tangled around my neck.
Hi Ed,Originally Posted by Ed Richards
Just googled it too...
Yikes!
LOL... Another reason for having a BIG darkcloth?
Cheers
Life in the fast lane!
I'm fortunate to be myopic - I take my glasses off to see the groundglass with nose almost touching. Of course I can't see anything else without my glasses...
At your service, Darr and Capocheny ...
Maybe a little explanation is in order. You are getting presbyopic, which is another way of saying that your eyes are losing their ability to focus on near objects. Bifocals are one way of correcting this with glasses, wherein the lower part of the glass, the little ground-in window, provides plus strength that your eyes can't exert any longer. To check focus on the ground glass, you'd have to look through this part of your bifocals, which CAN be a pain in the neck, literally. BTW, this applies even if you use a loupe. Formerly, you had glasses that corrected for far objects and accommodated your eyes to see near ones, but these glasses are not of much use under the dark cloth now. Neither are contact lenses, because they also correct for far. When I tried to fit so-called multifocal contact lenses to patients of mine, I've never met with much success or enthusiasm. They seem to not work so well.
HTH!
Christoph
Christoph -
Thank you for your very understandable explanation. My contacts are 'multfocal' and my doctor was surprised that I can read better with them than my glasses, but the distance is not so good. When I questioned him about any particular reason why I would have trouble focusing through a lens with the contacts on, he said it was probably due to the 'multifocal' lens. He also told me that more than 90% of his patients cannot wear multifocals either. I guess I am lucky here since I spend a lot of my free time reading and I can actually read the best with the contacts on, just do not ask me to drive!
Kind Regards,
One of the advantages of being highly myopic is that you can put your eye(s) very close to the gg without any glasses. After cataract surgery, my far vision is close to 20/20, without glasses, but of course I need glasses for near vision. I managed to talk my opthamologist into giving me a prescription for +5 diopter reading glasses to be used with my view camera. That allows me to get about 7 inches from the gg. Ideally I would like to be able to get about 6 inches from the gg, because the point of view would correpsond to viewing an 8 x 10 print at 12 inches, but she objected in anything stronger because of potential problems with binocular vision.
Still, I do pretty well with these glasses. I seldom need to use a loupe. I choose a near point and a far point and focus about halfway in between, although I may vary that depending on the scene and what seems most important to get in good focus. Whenever you view the gg, your eyes have an effective circle of confusion, the size of which depends on how close you are to the gg. At about 6 inches, it should be comparable to the coc you use for depth of field calculations. Since the deph of focus (distinguished from depth of field) is proportional to the coc diameter, and since you can't really distinguish one position from another within that range, there is a limit on how precisely you can focus. If you use a loupe, you reduce your effective viewing coc, which lets you focus more precisely. The interesting thing is that I appear to do very well with my method, despite the fact that my focusing error should be at best something like half a mm (with a relative aperture of f/5.6) and may be much larger. I think this is because I've developed several compensating mechanisms. Thus when I focus on the near and far points I approach them from opposite directions, which means I tend to overshoot about the same amount. The errors cancel when taking the midpoint. I may also focus several times on each and end up using an average position and that tends to reduce focusing errors even more. And of course stopping down a stop or two more than absolutely necessary will compensate for small focusing errors. On some occasions, none of this works and I need to use the higher magnification a loupe provides. This is particularly true with wide angle lens far from the center of the field.
I am pretty nearsighted, and now need reading glasses, so I wear progressives. My eye Dr. gave me a prescription for progressive glasses that has the far vision portion at the very top of the lens, and progresses to close distance at the middle of the lens, with an extra close up portion at the bottom. This is much more comfortable than trying to focus or look at the GG using the very bottom of your eyeglasses. I carry them in my backpack, and just pop them on when I start photographing. Then I leave them on until I am done with my photography. It took a little bit of getting used to looking through the top of the lens for most normal vision, but it is much easier to use these glasses under the dark cloth than my standard glasses. To save money, I used an old frame. I am happy with this solution, at least so far. I used to have to take my glasses off to look at the overall composition, and put them back on to use the loupe. Well, since composition and focusing is often an iterative process, this was a real pain. This new solution seems to work very nicely.
If you want to try this, and want to make sure that the prescription is right, bring your camera, dark cloth, a lens, and your tripod to the eye Dr. and show the Dr. how you work. That way he or she can see how far you like to be from the GG when looking at the whole scene. That will help make sure that this portion of the prescription is placed close to the center of your lenses. It would probably be a good idea to warn the Dr. that you are doing this so that they can account for the extra time in scheduling their appointments.
Elsewhere on this forum, I remember that we had a discussion about glasses that plumbers use, with the close distance on the top, and the far distance on the bottom. It might be worth searching the forum for that one if you are interested. I discussed that with my Dr., but we came up with the above idea instead.
Last edited by David Karp; 26-Jul-2006 at 07:29.
I also went the route of having my opthamologist (sp?) create a pair of glasses for looking at the gg. I can't remember now (Another by-product of advancing years) but I think I had them created with 4X or 6X; the equivalent of a loupe. Similar to Leonard, they are set up to be a certain distance away from the gg. It beats having to peer thru a loupe and frees up a hand. Expensive but I love them.
If you go this route, be aware that because of the magnification, the glasses have to be made using round-ish lenses (according to my opthamologist). So, it's a bit harder to look over the top of them. Another criteria is to pick a frame where the lenses aren't too far apart since one tends to cross their eyes a bit when looking at the gg up close. If the lenses are too far apart, you end up looking thru the edges of the lens which have less light/more distortion.
And, don't be standing on the edge of a cliff when you come out from under the dark cloth with the glasses still on
Bob,
That is interesting. I never considered having a pair of glasses made that would substitute for a loupe. Mine are more general purpose. I still have to use a loupe for critical focusing. I don't mind that, so long as I don't have to work with three systems - eyes alone, eyes and glasses, and eyes, glasses and loupe.
For 8 x 10 and larger I use 3.25 pharmacy glasses (no loupe). My eye doctor worked with me on this. He decided the 3.25s would work fine as long as I did not have any problems with convergence. I do not. If I did he said we could make a similiar set of glasses helping with the convergence.
For 4 x 5 I have to use a loupe also.
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