Archived posting to the Leica Users Group, 2006/11/16

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Subject: Was RE: [Leica] M8 Impressions now Eye stuff
From: hoppyman at bigpond.net.au (G Hopkinson)
Date: Thu Nov 16 21:42:20 2006

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
>>>
>



Replies: Reply from rclompus at mac.com (Richard Clompus) (Was RE: [Leica] M8 Impressions now Eye stuff)
In reply to: Message from rclompus at mac.com (Richard Clompus) (Was RE: [Leica] M8 Impressions now Eye stuff)