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LiquidLight
09-07-2005, 02:04 PM
i cant decide what pinhole size to use.
i want f/280.. but to get 0,25mm pinhole is just crazy!
lenox got it but too ship it too Norway will cost me $100,75 (total)

Josh
09-07-2005, 03:30 PM
You can use any size you like and it will result in an image. 0.4mm will be closer to the optimum pinhole size and far easier to make. You could go for a comprimise and round up to 0.3mm = about f230, which will give you slightly differing results. Failing that poke some holes in foil and see which works the best.

LiquidLight
09-07-2005, 03:35 PM
what is optimum pinhole size?
why are there a optimum pinhole size?
what is it? * *:-/

murrayatuptowngallery
09-08-2005, 05:22 AM
There are different theories, and they all seem to depend on wavelength of light too. Lenses are certainly wavelength dependent, but we take that for granted with many modern lenses that are optimized for different wavelengths.

If you don't like math, try www.pinhole.cz, David Balihar's downloadable calculator.

If you want to see a derivation of optimal pinhole diameter, which you can then mutate into optimal distance for a non-optimal pinhole, search for PinPlus cameras. Paul Prober has a discussion on this topic.

Basically it has something to do with two main contributions to blur in the image, each mathematically dependent on something. If the sum of the contributing equations is analyzed via calculus to find nulls in the result, minimal blur, or maximum sharpness results. He goes on to discuss how this changes with macro/closeups, analogous to correction factor for bellows extension and macro work. He claims apparent origin to this derivation by assigning his name (along with someone else), in the form of a Prober-Wellman equation. I ran in to another pinholer who says he posted info on this years earlier, however.

Anyway, I ignored it the first few times I saw it, but one day decided to see where it led. I discovered that my 35mm conversion with an aperture stuck where I could make it fit without vignetting, non-optimal per equations, is actually optimal at about 0.6 m instead of 'infinity'. This might explain why my images are always sharper for closeups.

Anyone else see this with their cameras, disproving my observation (maybe I'm rationalizing it)?

earlj
09-08-2005, 07:27 AM
My favorite optimum pinhole size calculation is from Chris Patton-http://isaac.exploratorium.edu/~pauld/summer_institute/summer_day3eye_and_brain/pinhole_optimum_size.html#mulch

The formula is d = ( 1.22*2*W*L )^0.5
where d is the pinhole diameter in meters
W is the wavelength of light in meters
L is the focal distance in meters

which gives .309 mm for a 70 mm focal length (using 560 nm as the light wavelength - an arbitrary number in the middle of the visible spectrum). My 75 mm camera uses a number 80 hobby drill, which is .343 mm (a little big by this calculation), but it seems to work just fine. It would give good results with a 70 mm camera as well.

A number 12 needle should give you .350 mm, and this will be plenty close enough also.

LiquidLight
09-08-2005, 08:17 AM
i have to say that you guys know what your doing!
thanks for the help... for now..

and i am out of here. (getting a number 12 needle)



Ole.

LiquidLight
09-08-2005, 12:27 PM
the werdest thing.. * * they dont got a number 12 needle. *:'(
and i just cant wait to try out my new camera.


Ole.

GeeFoto
09-08-2005, 01:30 PM
Don't care much about ideal pinhole size.Smaller pinhole gives better sharpness.Use very thin material, like aluminium foil, and observe the pinhole's roundness with a scanner or a magnifier.You don't have to pay much money for good results.Make your own pinhole. :)

moot
09-08-2005, 03:05 PM
the werdest thing.. * * they dont got a number 12 needle. *:'(
and i just cant wait to try out my new camera.

Needles are tapered, so even if you are working with a needle that is too large, just don't push it in all the way. If you have a good loupe, or some fairly high powered magnifier (like a Hastings triplet) you can get a pretty good estimate of hole size by just laying a millimeter scale next to the pinhole and comparing the hole to a 1 mm increment. It's crude but it works fairly well to get started. You can be more precise later if you choose.

If you still want a #12, go to a craft store and look for beading needles. The package I bought had sizes from #10 - #15.

I'd take Josh's advice, punch a small hole and try it. You might be surprised how well any small hole will work.

ImageMaker
09-08-2005, 05:00 PM
Don't care much about ideal pinhole size.Smaller pinhole gives better sharpness.

Actually, it's pretty easy to see the loss if you make the hole a lot too small -- diffraction spreads the light and puts a "fuzz" over everything, a general softness that's a little different from the minimum visible feature size introduced by a too-large hole. OTOH, you have to be quite a bit too small to see this -- 20%, at least, maybe more if the optimum hole is relatively large.

taco
09-08-2005, 07:34 PM
I also work with all kinds of shoe boxes, coffie tins etc and even if the pinhole size is not optimal, I try to make them all using more or less the same f-stop. It's just easier when you run around carrying a lot of boxes loaded with paper: One small calculation fits for all
taco

taco
09-09-2005, 12:43 PM
I also work with all kinds of shoe boxes, coffie tins etc and even if the pinhole size is not optimal, I try to make them all using more or less the same f-stop. It's just easier when you run around carrying a lot of boxes loaded with paper: One small calculation fits for all
taco
Forgot to mention: f/170
taco

LiquidLight
09-10-2005, 12:46 PM
My favorite optimum pinhole size calculation is from Chris Patton-http://isaac.exploratorium.edu/~pauld/summer_institute/summer_day3eye_and_brain/pinhole_optimum_size.html#mulch

The formula is d = ( 1.22*2*W*L )^0.5
where d is the pinhole diameter in meters
W is the wavelength of light in meters
L is the focal distance in meters

which gives .309 mm for a 70 mm focal length (using 560 nm as the light wavelength - an arbitrary number in the middle of the visible spectrum). My 75 mm camera uses a number 80 hobby drill, which is .343 mm (a little big by this calculation), but it seems to work just fine. It would give good results with a 70 mm camera as well.

A number 12 needle should give you .350 mm, and this will be plenty close enough also.




how small is a number 16 needle?

earlj
09-10-2005, 05:58 PM
My size chart for needles does not go smaller than #12. That is a pretty small needle. I posted needle sizes previously:

http://f295.tompersinger.com/cgi-bin/Blah/Blah.pl?,b=cm,v=display,m=1108331510,s=1,highlight =needle#num1

I think that when you need holes smaller than .35 mm, you might be better off ordering the laser - drilled holes.

But this discussion has reminded us all, over and over, use whatever hole you can get. Make the best hole you can, and use it. I think that all this fuss over the perfect hole for a given focal distance is a bit overblown. I have found that the bigger the negative, the better I like the results. If you are making contact prints, then you will be happy with whatever hole you have, as long as you can calculate the exposure accurately.

Nick
09-12-2005, 02:45 AM
I bet for 0.3mm

taco
09-12-2005, 03:46 PM
I think that when you need holes smaller than .35 mm, you might be better off ordering the laser - drilled holes.
Laser drilled pinholes are expensive ::)
Long ago (1997) I bought a set of "micro-drilled" pinholes , at that time distributed by the pinhole resource of E.Renner, but they stopped with the distribution. Just had a look on the leftover and found the name of the manufacturer back and also a link to him::

bubba@mail.wiscnet.net
This is the email address for a guy in Wisconsin who makes custom drilled apertures, pinhole camera body caps and aperture material. His address is:
Christiansen Gallery
Minute Aperture Imaging
7586 County H
P.O. Box 313
Maplewood, WI. 920.856.6842
(link: http://www.hastings.k12.ny.us/PDI/pinhole_links.htm)
Can't remember exactly what I paid for them, but somewhere between 20 and 30 US$ for a set of 8 holes!
Slightly cheaper then Lenox ;D
taco

LiquidLight
09-12-2005, 05:09 PM
thank you taco!!



Ole.

taco
09-13-2005, 07:26 PM
Forgot to mention: f/170
taco

o.k. I said more or less So my f/170 is similar to the f/175 :)
We are not in Florida here, last votes still have to be counted, but I believe that the coalition 175+170 is winning ;D
taco