Posted by Dean on February 28, 2001 at 07:00:23:
For my shooting glasses,
I have a white cover disk and a black cover disk (to cover my non-shooting eye).
Does anyone know the conventional wisdom (if in fact there's a prevailing view)
for when one should typically use the white disk and when one should use the
black one? If it matters, I use a clear, no-power lens in front of my shooting
eye.
Thanks in advance for the advice.
Posted by Grzegorz on February 28, 2001 at 07:54:27:
I had a similar
problem (I shot air rifle). I heard many advise to use a white cover for
nonaiming eye. I reconsidered this and now I think that one should use any white
cover for pistol shooting and black one for rifle. When aiming with pistol you
have large amount of light coming to your aiming eye. If you put a black cover
on nonaiming eye there will be a huge difference between conditions at which
your both eyes work. Covered eye "wants" to enlarge a pupil whereas aiming eye
wants opposite. They are in "fight" and this is surely not we want to get
:-)
When shooting rifle there is a very small amount of light coming to your
aiming eye, so the same should be with a other - use black cover.
Grzegorz
For smallbore, esp prone, I had some success and comfort with a
black blinder. Eventually, I found that the blinder severely limited my ability
to track wind changes. My field of view was severely restricted. I compromised.
Lately I've used a dark prescription lens on the non-aiming eye. I can avoid the
gross distractions of light while still seeing the better part of the range for
wind etc.
I use adjustable shooting glasses. The non-aiming eye has a large
lens to afford better eye protection. Both lenses are clear. I attach a colored
filter to the non-aiming lens when outdoors, esp. in strong light etc. Indoors I
tend towards no filter, and prefer a white or opaque blinder. Mostly for
avoiding distractions. It seems to me that when we stop down the rear aperture
of the rifle sight we increase depth of field. This should be true for eyes as
well. Perhaps it's best to manage just enough light entering both eyes to keep
our eyes "stopped down" a bit to help improve depth of field.
After years of
shooting with the blinder hat, and a black blinder on the non-aiming eye, I came
to the conclusion that the struggles I encounter while trying to stay on top of
wind changes were a liability when compared to the minor comfort attained with a
totally black sighting area.
I must admit that I am confused about the eye
and depth of field though. When a camera lens is stopped down the depth of field
increases. When I look though a stopped down aperture I think I get a better
sight picture. However, this also means less light entering my eye and the iris
should respond by opening.
How is it then that the stopped down aperture
seems to improve my perception of depth of field while the reduction in
transmitted light should be opening my iris and reducing depth of field?
Dean
Peterson
Posted by PGFaini on February 28, 2001 at 12:03:27:
Because depth of
field, is controlled by the f-stop. This is the ratio between the focal length,
and the aperture. The iris diaphragm, or aperture sight, is acting like a lens,
in that this ratio is between it's distance to your retina, and it's diameter.
No matter how much your eye's iris dilates, it can't change this focal length,
or the light transmission (if the aperture's diameter is less than your eyes
pupil diameter). The depth of field only increases when the aperture diameter
becomes smaller than the eye's pupil diameter.
At least this is what I
think, I'd sure like other opinions.
Paul
Posted by Andy Wai on February 28, 2001 at 11:40:49:
Well, the reason why
something on a flat project image is out of focus is a single point from the
subject converges to a point either in front or behind the image plane.
Therefore, the point is enlarged to a circle at the image plane. Stopping down
the lens decreases the size of its aperture and correspondingly decreases the
size of the circle at the image plane. Eventually, the circle will be small
enough that you can't tell it's not a point. That's how you get depth of field
effect.
Now you don't actually need to reduce the size of the lens itself, as
long as the diameter of the beam from outside is reduced, you have the same
effect. In the case of the eye, you normal use as much of the lens' area as the
iris would allow. But if you put an artificial iris in front that's smaller, it
will restrict the beam width further and increase the overall dof.
Andy Wai
P.S. Wow, I haven't shot with films for quite a while now and I still
remember all these... :-
Posted by kmerrill on February 28, 2001 at 12:19:34:
Thanks for asking
this, I was about to ask the same question. The other postings explains why
after shooting when I went out side to get my dog, and it was dark, I would go
almost blind in my shooting eye for about 60 seconds, once out doors. But since
I changed over to the white disk this problem went away.
Posted by Doug White on February 28, 2001 at 19:53:14:
For pistol, the
best thing to use is neither. You want the same amount of light going into both
eyes, but you don't want to be able to see the sights/target with the
non-shooting eye. If you wear regular glasses, a small piece of Scotch tape
works fine. Fold over the last 1/4" to make a non-sticky tab, and it will be
easy to remove. The tape can be quite small, which will allow you to use both
eyes when looking down at the bench for loading & such. If you use fancy
shooting glasses, see if you can get a frosted disk.
For rifle, there is
very little light getting into the shooting eye because of the peep sight, so a
black disk si probably OK. The main thing is to try and maintain balanced
illumination between the two eyes. I've read that your eyes are cross-wired
enough that blocking all of the light into one eye can significantly affect the
vision in the other one.
Doug White
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