Archived posting to the Leica Users Group, 2006/11/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Thanks very much, Richard, that's very helpful and interesting. I like to understand as much as possible. Did I read you correctly that the uncorrected camera requires me to focus to + 0.5 to see objects at infinity as though they were two metres away? Pardon me if I am being dense. I am actually 51. My master eye is quite dominant and the habit of putting eyepieces and sights up to there is strongly ingrained. For non-optical systems, I need the focal point to be just at arms length, of course. I do need distance correction with both eyes. A -1 and a -1.5 camera eyepiece are progressively worse for me, as you predicted. The smallest correction that I can obtain off the shelf from Leica is -.50. The bare camera seems to be a little sharper for me. I have the -.50 on hand so perhaps I need to look again more carefully. I've never been comfortable using glasses with any eyepiece. I like to scrunch that eyeball hard up against the eyepiece to see the full frame and also help seal out light from the sides. The trouble these days is that my near vision makes the controls less than sharp as well. Another reason why LCD screens and fiddly controls on digitals are difficult for me! Thanks again for taking the time to provide your response. I shall delve into the archives on this, as well. Cheers Hoppy -----Original Message----- From: lug-bounces+hoppyman=bigpond.net.au@leica-users.org [mailto:lug-bounces+hoppyman=bigpond.net.au@leica-users.org] On Behalf Of Richard Clompus Sent: Friday, 17 November 2006 14:54 To: Leica Users Group Subject: Re: Was RE: [Leica] M8 Impressions now Eye stuff Hoppy, let me try to shed some light on this subject. :-) If your dominant eye is -0.50 diopter, that means you have a mild amount of nearsightedness (myopia) in that eye. This will create a very mild amount of distance blur in that eye. If you're other eye is fine (no blur), you probably won't notice any blur when using both eyes together. Your brain will automatically use the clearer of the two eyes so that your "perception" of the world is clear. I've seen many patients over the years that had quite blurred vision in one eye but were not aware of it until you have them cover the clear eye and ask them read the eye chart. Then they seem shocked. Brains tend to adapt well to blur in one eye which helps with survival. Also keep in mind that a little blur looking straight ahead has no impact on your peripheral vision. Peripheral vision is always blurred and is essentially there to detect motion - like noticing the saber tooth tiger sneaking up on your left side. Many camera systems are designed so that the user must accommodate (or focus) a little bit to see the distance. Human visual systems seem to prefer this minimal focus requirement. In many cases, just putting something close to your eye stimulates your visual system to focus a little. If you are less than 40-45 years old, your eye will focus this small amount automatically without you being aware. The camera's optical system presenting infinity at a virtual point 2 meters in front of the camera. You eye must focus 0.50 diopter to see this point in space clearly. When you combine the mild nearsightedness (-0.50 diopter) in your viewing eye with the -0.50 diopter focussing requirement of the viewfinder, you might think you would need a -1.00 diopter correction lens. Well, it's not that simple. You would be way over-corrected with a -1.00 diopter eyepiece lens and although the viewfinder might seem clear when first viewing through it - you would not be comfortable. Your eye's focussing system would be working too hard. If you're over 45 years old, you would definitely be uncomfortable. If the rangefinder is blurred when viewing without your glasses, I'd recommend you start with a -0.25 diopter (if available) or -0.50 diopter corrective eyepiece lens to produce clear vision through the camera's rangefinder. Use the least amount of minus lens power to clear the image in the rangefinder. Many eyepiece corrective lenses only come in 0.50 diopter increments. You have probably been selecting lenses that are too strong for you. Better to be under corrected than over corrected. Weaker is better. Fortunately you don't have astigmatism. That's another 3 paragraph explanation. :-) I know this is a long winded answer but I hope it helps understand some of the aspects of vision and photography. All the best, Richard On Nov 16, 2006, at 7:26 AM, G Hopkinson wrote: > Hi Richard, firstly my apologies if this is an imposition. Can you > provide a basic summary of how M viewfinders and eyepieces relate > to eye glasses corrections? > Each time I have an eye check up or new glasses, I try to quiz my > optometrists, however, it is evidently out of their normal area. I > understand that the uncorrected viewfinder on an M7 is -.5 dioptre. > There are a number of (expensive) corrective lenses but I am > steadily going broke having to buy them untested to try out. Should > the total of correction (camera plus correction eyepiece)equal > the glasses distance correction for the master eye? Or do I have it > all muddled? I'm told that my master eye prescription is -.5 > with no astigmatism. I need correction for both reading and > distance. I use progressives. I have never been able to use glasses > with > cameras and so would like to have the same correction through the > finder, as though they are on. > Cheers > Hoppy > > -----Original Message----- > From: lug-bounces+hoppyman=bigpond.net.au@leica-users.org > [mailto:lug-bounces+hoppyman=bigpond.net.au@leica-users.org] On > Behalf Of > Walt Johnson > Sent: Thursday, 16 November 2006 22:03 > To: Leica Users Group > Subject: Re: [Leica] M8 Impressions, Pro and Con, correction > > Richard > > I had a lens replacement as you described several years ago. First > thing I noticed was the world's exciting colors and clarity when view > with my right eye. There was noticeable difference between my new > right > eye and the vintage left one. I was concerned about judging colors > accurately but solved the problem by going back to Tr-X. :-) > > Walt > > Rockledge, Fl...(where is Ponte Vedra Beach?) > > Richard Clompus wrote: > >> Tina, as an optometrist, I've had many patients over the years that >> had your exact complaints. Glad to hear your eyes are healthy. You >> are explaining the effects of mild changes in the clarity of the >> crystalline lens in each eye. As we grow older (and wiser), the >> protein in the lens slowly loses its transparency. Things are not as >> bright or clear even though your vision may still be 20/20 with >> glasses. This is perfectly normal. Over time, the lens can become >> dense enough that it decreases vision and it can then be removed >> surgically and replaced with a new one made of plastic. After >> surgery, Its amazing how patients report how bright colors are before >> commenting how clear things look. The cloudy lens that is removed is >> called a cataract. Lenses don't become cataracts overnight - it >> takes years. Night driving and glare often worsen as the lens >> becomes more cloudy. >> >> Fortunately, rangefinder focusing is easy and autofocusing is even >> easier. Glad to hear you're doing fine. Your photographs and >> enthusiasm for photography are something to be admired. >> >> Richard >> >> Richard Clompus, OD >> Ponte VEdra Beach, FL >> >> >> On Nov 15, 2006, at 3:25 PM, Tina Manley wrote: >> >>> LUG: >>> >>> Disregard this comment that I made about the M8: >>> >>> "Either the viewfinder is dimmer than my M7's or my eyes are >>> getting >>> worse (a possibility!) It's harder to get the focus right than >>> with >>> the M7." >>> >>> I just got back from having my eyes checked and the vision in my >>> left eye has decreased 20% since my last check-up! The doctor >>> checked for glaucoma, cataracts, macular degeneration and all kinds >>> of stuff and found nothing. I'm going back next week another test >>> and some new glasses. My focusing with the M8 should improve >>> immensely when I have glasses that match my new decreased vision. >>> Getting old sucks but it's better than the alternative!! >>> >>> Tina >>> >>> Tina Manley, ASMP, NPPA >>> http://www.tinamanley.com >>> >