Bad eyes, diopter? (and Vuescan)

  • Thread starter Thread starter AAvK
  • Start date Start date
A

AAvK

I have diabetic neuropathy in my optic nerves, which is sugar crystals in there
and that messes-up eyesight. But glasses do work fine to correct my vision.

I seem to notice that my images (35 slides) look sharp under a loupe, then I
scan them and they come up fuzzy! My older 6x7 positives are alright, but not
my recent 35s, and I take time focusing.

Maybe I am getting pixel bloom in scanning from overdone settings in Vuescan?
Overworking the CCD? Settings too intense?

Or maybe I am focusing the lens to the wrong length, using the lens as like my
eye glasses, or in another term; focusing to the same prescription of my
glasses, and therefore the images are a bit fuzzy? Is that exactly what diopters
are for?

If so I need a -1.25 for my Pentax K2 and I don't know where to find one.
I would appreciate any positive advise, please.

TIA,
 
AAvK said:
I have diabetic neuropathy in my optic nerves, which is sugar crystals in there
and that messes-up eyesight. But glasses do work fine to correct my vision.

I seem to notice that my images (35 slides) look sharp under a loupe, then I
scan them and they come up fuzzy! My older 6x7 positives are alright, but not
my recent 35s, and I take time focusing.

Maybe I am getting pixel bloom in scanning from overdone settings in Vuescan?
Overworking the CCD? Settings too intense?

Or maybe I am focusing the lens to the wrong length, using the lens as like my
eye glasses, or in another term; focusing to the same prescription of my
glasses, and therefore the images are a bit fuzzy? Is that exactly what diopters
are for?

If so I need a -1.25 for my Pentax K2 and I don't know where to find one.
I would appreciate any positive advise, please.

TIA,
Click to expand...

I don't know where to get dioptors, but many cameras have diopter
adjustments built into the viewfinder. You might want to check out
something like that.
 
AAvK said:
I have diabetic neuropathy in my optic nerves, which is sugar
crystals in there and that messes-up eyesight. But glasses do work
fine to correct my vision.
Click to expand...

I'm not an expert, but that seems odd. Glasses just correct for focus
aberrations.
I seem to notice that my images (35 slides) look sharp under a
loupe,
Click to expand...

How much magnification?
then I scan them and they come up fuzzy! My older 6x7 positives are
alright, but not my recent 35s, and I take time focusing.
Click to expand...

Seems to indicate an issue with your 35s, maybe you use different ppi
settings between 6x7cm and 35mm?
Maybe I am getting pixel bloom in scanning from overdone settings in
Vuescan? Overworking the CCD? Settings too intense?
Click to expand...

The histogram will reveal scanner blooming, because it is related to
highlight clipping.
Or maybe I am focusing the lens to the wrong length, using the lens
as like my eye glasses, or in another term; focusing to the same
prescription of my glasses, and therefore the images are a bit
fuzzy?
Is that exactly what diopters are for?
Click to expand...

The camera diopters allow the eye to focus without glasses.
If so I need a -1.25 for my Pentax K2 and I don't know where to
find one. I would appreciate any positive advise, please.
Click to expand...

A camera shop?
 
Bart sorry for being late here...
I'm not an expert, but that seems odd. Glasses just correct for focus
aberrations.
Click to expand...

Eye glasses?
How much magnification?
Click to expand...

4x coated glass optic.
Seems to indicate an issue with your 35s, maybe you use different ppi
settings between 6x7cm and 35mm?
Click to expand...

Nope, whatever gives me a final 300 ppi in Vuescan, larger dimensions for
the 6x7cm films.
The histogram will reveal scanner blooming, because it is related to
highlight clipping.
Click to expand...

Thanks for that, I don't quite know how to read a histogram, much less
pick out the bloom from it.
The camera diopters allow the eye to focus without glasses.
Click to expand...

Makes sense!
A camera shop?
Click to expand...

Yep, the local cam shop can order me a genuine SMC one for $24, as I
found out. But not to my exact perscription. I can get a -1.00, my eye
is -1.25, will that matter?
 
AAvK said:
Yep, the local cam shop can order me a genuine SMC one for $24, as I
found out. But not to my exact perscription. I can get a -1.00, my eye
is -1.25, will that matter?
Click to expand...

Look for a variable diopter. I see them going to -2. Google "variable
diopter".

LD
 
AAvK said:
Bart sorry for being late here...

Eye glasses?
Click to expand...

Yes. They correct for focal distance limitations caused by the shape
of the eye ball or the inability of the eye lens to change shape
enough.
4x coated glass optic.
Click to expand...

You'll need something like an 8x magnification to judge critical
sharpness of 35mm film. A 4x magnification is good for a full image
view, but not good enough to check for defocus and such.

SNIP
Thanks for that, I don't quite know how to read a histogram, much
less pick out the bloom from it.
Click to expand...

If there is an abundance of signal counts in the highest bin, there is
an increased chance of charge spilling over to adjacent sensels, thus
causing blooming.
I can get a -1.00, my eye is -1.25, will that matter?
Click to expand...

Well, it won't be perfect. Wearing glasses is a bit of a compromise,
it can correct for most focal deficiencies, but it will be physically
in the way when trying to look through the viewfinder.
 
Bart van der Wolf said:
If there is an abundance of signal counts in the highest bin, there is
an increased chance of charge spilling over to adjacent sensels, thus
causing blooming.
Click to expand...

That's much clearer now ;-)
 
AAvK said:
Yep, the local cam shop can order me a genuine SMC one for $24, as I
found out. But not to my exact perscription. I can get a -1.00, my eye
is -1.25, will that matter?
Click to expand...

FYI, if your eyeglasses have anything beyond basic adjustment, the
diopter may not help. E.g., it won't correct for astigmatism (which has
a specific axis).

The difference between -1.00 and -1.25 would keep you from seeing sharp
vs. tack-sharp focus.

Depending on how much you want to sink into this project, you could find
an eyepiece adapter and have a prescription lens ground to shape and
inserted. But if you have astigmatism or other axis-specific
correction, you won't be able to rotate the camera from landscape to
portrait and still see through it. :-) (An easy test for this is to
rotate your eyeglasses 90 degrees and look through them.)

Cheers,
Richard
 
Richard H. wrote:

Depending on how much you want to sink into this project, you could find
an eyepiece adapter and have a prescription lens ground to shape and
inserted. But if you have astigmatism or other axis-specific
correction, you won't be able to rotate the camera from landscape to
portrait and still see through it. :-) (An easy test for this is to
rotate your eyeglasses 90 degrees and look through them.)
Click to expand...

Oh dear...

Why does the world not do that when I take mine off and rotate my head?
 
Some Pentax cameras, came with a -1.00 (ME Super) and -0.50 (MX) diopter
lens in the viewfinder.

You may want to check the K2 specifications in your user manual before
you order.

Jim
 
AAvK said:
I have diabetic neuropathy in my optic nerves, which is sugar crystals in there
and that messes-up eyesight. But glasses do work fine to correct my vision.

I seem to notice that my images (35 slides) look sharp under a loupe, then I
scan them and they come up fuzzy! My older 6x7 positives are alright, but not
my recent 35s, and I take time focusing.
Click to expand...

When you say "recent" do you mean that at some time in the past you were
getting acceptable results and now you're not? If this is the case then
possibly there's a problem with the scanner or a software setting. You might
try changing the unsharp mask setting.

Or maybe I am focusing the lens to the wrong length, using the lens as like my
eye glasses, or in another term; focusing to the same prescription of my
glasses, and therefore the images are a bit fuzzy? Is that exactly what diopters
are for?

If so I need a -1.25 for my Pentax K2 and I don't know where to find one.
I would appreciate any positive advise, please.
Click to expand...

There are viewfinders that offer continously variable diopter settings in
the range you need
but they don't fit your camera. Here's one for the Pentax LX:
http://www.bhphotovideo.com/bnh/con...ls&Q=&sku=41085&is=USA&addedTroughType=search

I don't know if you can use contacts but if so that might be a useful aid to
focussing. I don't think focussing is the problem with your scans not unless
you only shoot wide open and never stop down your lens. DOF latitude
provided by stopping down should compensate for minor errors in focus.
Good Luck,
photog
 
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