Calculating pinhole-size

[europanorama]

Received a Polaroid MP3 with pinhole taped into board-hole.
When bellows are closed i calculared 40mm FL.
If i am holding led-light(one pin) directly onto pinhole it will be projected to groundglass.
Can the size of this projection tell me the size of the pinhole?
How ist it calculated?
pinhole-size leads to a certain FL-range i was told.

NB: Shinkphoto/skinpinhole has a copal-0-set with pinhole, Zone Plate an Zone sieve. If no shutter is used 30mm hole must be drilled into lens-board. NB; ist linhof 82.5 x82.5mm

 

[bernard_L]

If i am holding led-light(one pin) directly onto pinhole it will be projected to groundglass.
Can the size of this projection tell me the size of the pinhole?

No. LED is not a point source; even if it were, its light rays are not parallel: they diverge; and even if they did not, diffraction makes the light spot larger than the pinhole.

You can try to measure the pinhole size using a s***r [edited to meet apug requirements; hope you still understand what I mean], preferably in tranparency mode.

 

[kier]

Yeah Bernard has the right idea - best way is to use a flatbed image capture device attached to a computer (that shalt not be named on this site) and determine it that way. There's numerous resources on the web about how to measure a pinhole size in this way.

Another way is to take 2 photos - one with the bellows collapsed and one with the bellows extended. Use a pinhole calculator to determine the best pinhole size and aperture for each focal length and expose for that aperture. The assumption here is that whomever put that pinhole made it the right size for one of those focal lengths. Note that it doesn't appear that there's a "shutter" on there, so unless you afix one, you'll be exposing from the time you pull the dark slide.

 

[DWThomas]

If you have an enlarger available you could set it up for a known magnification, ideally in the 5x to 10x range. Insert the pinhole plate as a negative, measure the projected "enlarged" image of the hole, and divide the reading by the magnification. While we love to be accurate, three digit precision isn't necessary for pinhole work.

 

[pdeeh]

they mean scanner
scanner
scanner
scanner

but I have to add, I found the enlarger method very satisfactory.

 

[TheToadMen]

If you have an enlarger available you could set it up for a known magnification, ideally in the 5x to 10x range. Insert the pinhole plate as a negative, measure the projected "enlarged" image of the hole, and divide the reading by the magnification. While we love to be accurate, three digit precision isn't necessary for pinhole work.

There is an other way to use an enlarger or a lamp (without know magnification factor).

1) Take a blank piece of film and draw a line of 10 mm (with a permanent marker or so).
2) Put it in the enlarger, turn it up (then lock) and project the line.
3) Measure the projected line (= X) in millimeters (mm)
4) You can calculate the magnification factor: M = 10/X
5) Now put the pinhole in the enlarger (still locked in the same position) and project the pinhole.
6) Measure the diameter of the projected circle (= Y)
7) To get the real pinhole size (P) just calculate: P = M*Y (in mm)
8) If you want inches: 1 inch = 25.4 mm and 1 mm = 0.039 inch

Example:
The projected line is 480 mm in length?
Then the magnification factor is: M = 10/480 = 0,0208

The diameter of the projected circle (Y) is 50 mm wide?
Then the real pinhole size is: P = M*Y = 0,0208*50 = 0.104 mm (so let's just say 0.1 mm)

Transfer into inches? 0.104 mm * 0.039 = 0.004 inch

 

[MattKing]

You can try to measure the pinhole size using a s***r [edited to meet apug requirements; hope you still understand what I mean]

APUG welcomes discussions about using scanners or other sorts of digital equipment for purposes like this.

It is only discussions about that other sort of photography that are asked to move on.

The pop-up cation is just that - a caution. Check that the subject of your post isn't off topic, and then post it as is.

 

[europanorama]

I think i will shoot. with xp2-400. first i will termine FL. can be done by measuring FOV.
Then i must shoot multiple exposures. Pinhole is taped in. dont want to remove.
Only a scanner is ready but not installed.
have another standard light source with reflector here. useless to calculate? and how is calculation done? distance to Filmplane is 40mm up to 240mm.
i want a new solution by using skinkpinhole or and zeroimage. hope ZI will sell pinholes alone.
BTW: the front-lenses-hole is 47x47mm only. ok nothing to do with pinholing. lensboard is 82.3 x 82.3mm. which standard is this? Thanks

 

[NedL]

I think the film size will be 4x5 or 3.25x4.25 inches, is this right? In my opinion you do not want to waste precious and expensive film, or your time, trying to figure out the best "FL" experimentally. I suspect you will be happier using a shorter FL with a wider FOV: long FL on small negatives seem to "lose something" and somehow are not very satisfying -- it is just a part of pinhole geometry. The rail below the camera might be in the way.

Do you have a ruler with mm markings on it? Hold it next to the pinhole and estimate. You do not need to use a magnifying glass ( unless you normally wear reading glasses ) but if you have one, that's fine. Just estimate how much of a mm the pinhole is. For your use, if it is around .25 mm or ..2 mm or even less, I think if will work for you. If it is bigger than about 0.3mm then I think you will find the images too soft ( with a wide FOV ). So, just look with your eyes and guess if the pinhole is 1/5 or 1/4 or 1/3 of a mm.

 

[europanorama]

I will use 6x7 graflex RH-50 since i have a lot of 70mm film. 2x 30m xp2-400(the old version). but right i have a ruler inside a loupe but it cannot resolve more than 0.5mm.
later i will use 4x5. have also a 6x9 back vertical-the Korona. can shoot 240 images.
Would like to have a 4x5 to graphic(RB)-adapter vertical. to use mamiyas vaccum back.
Best would be a projection but inside camera, dont want to remove taped pinhole. I am on a concept using copal 0 to copal 1(dont have copal 0) from shinkpinhole/photo. 90mm
and other FL1 and shift)preshifted lensboards.
btw: i have made a graph showing which FL is related to which image-size/FOV. should transfer this to pc if i would know how to....

 

[europanorama]

Update:
FL is 63mm and pinhole size is 0.4 -0.5mm. i looked through lievview with luminar 63mm and added mm-scale. will do a shot. and compare ratios.
The selected focal length (distance between sensor / film and pinhole aperture in mm) determines the resulting angle of view. The shorter the focal length, the wider the angle of view. With the above table you can compare how wide a view you can obtain with with varying distances and film formats. The size of the pinhole aperture is always linked to the focal length. The same applies to the design of zone plates and zone sieves. Pinhole apertures in a given size can be used over a range of focal lengths without degration of image quality. With sizes 0.3, 0.4, 0.5 and 0.6 all ranges between wide-angle and tele photography can be covered. Zone plates and zone sieves however, should always match their calculated focal length as close as possible.
from here:
http://skinkpinhole.com/wp/webshop/shop/grossformat/#tab-description
He is telling that with pinhole Focallenght and size match over a range. I dont understand why he does not mention from 0.3 to 0.6. instead says:
With sizes 0.3, 0.4, 0.5 and 0.6 all ranges between wide-angle and tele photography can be covered
does he only have these size. maybe he can make inbetween.
but for zone plate and sieve FL and size must match:
Zone plates and zone sieves however, should always match their calculated focal length as close as possible.
when he mentions linhof lensboard 90mm does he mean lensboardsize?
That this mean my 82.5 x82.5mm from MP3 is special size ? or is it really linhof-standard?

 

[NedL]

I don't know about lens boards, but your pinhole between 0.4 and 0.5 mm will probably work well for FL between about 125 and 175mm.
To me, that seems a little long for the film sizes you are planning to use, but it is a matter of opinion, and depends what you like!
Have fun!

 

[europanorama]

http://mrpinhole.com/holesize.php
Its about matching what i calculated.
60-65mm . 65mm 0.34 f/191
my values 0.4- 0.5mm were guesswork. resolution was not precise enough. will lineup 0.5mm ruler.
will take a precise picture of the hole.

 

[Jim Jones]

. . . lensboard is 82.3 x 82.3mm. which standard is this? Thanks

[/QUOTE]

The lens board is 3.25x3.25 inches, 1/8 inch thick, a size used on many American press and large SLR cameras decades ago. They can easily be improvised from 1/8 inch or 3mm plywood or, for experimental use, from foamcore.

 

[europanorama]

Received a Polaroid MP3 with pinhole taped into board-hole.
When bellows are closed i calculated approx 65mm FL. CORRECTED(not 40mm)
If i am holding led-light(one pin) directly onto pinhole it will be projected to groundglass.
Can the size of this projection tell me the size of the pinhole?
How ist it calculated?
pinhole-size leads to a certain FL-range i was told. View attachment 158584
NB: Shinkphoto/skinpinhole has a copal-0-set with pinhole, Zone Plate an Zone sieve. If no shutter is used 30mm hole must be drilled into lens-board. NB; ist linhof 82.5 x82.5mm

63-65mm not 40mm min. bellows collapsed.
frame is 49x49mm approx.

 

[europanorama]

Have it now. took an 6x image with 35mm macrolens canon on contax macrostand.
pinhole is 4.54 mm
chip: 22.2mm
image-ratio 0.1056511
resulting in 4.54mm pinhole
http://www.mrpinhole.com/calcpinh.php
is telling: ideal FL 116mm f256
70.9 degr. 223mm image
on 4x5 inch 164mm diagonal
125 iso- sunny rule 2.04sec.
Pity i dont have it in shutter-could have prontor professional timer used.
but later when i have skinkpinhole(photo) copal 0(adapted for copal 1)
Shift: with shutter only +-5mm. Is it worth with 116mm 71°?
if only zeroimage would sell the shutter alone. with mentioned timer 2-32sec. exp. times possible.
Without shutter: +-19mm shift will wait until i have shinkphoto copal 1(30mm hole needed) set to see which shift is really possible with it.
but with zoneplate and sieve i need a shutter anyway. except when using ultra-low-speed-film.
first image showing mm-paper- 4.2mm horizontal shown
second image focussed on pinhole 0.455mm

 

[europanorama]

I am lucky have found a peak-loupe with multiple scales and even pinholes-on 0.1mm steps only but there is also a 0.1mm scale which is telling me that the pinhole here is right inbetween 0.4 and 0.5. could visualize by handholding against strong light! maybe on peak-site or elsewhere one can view the scales.

 

[TheToadMen]

peak-loupe with multiple scales

That's seems to be a handy tool. Could you post an image of it?
Maybe I can find one overhere.

 

[europanorama]

Will do later: Its called PEAK Scale Lupe 10x (Lupe is german). it has a transparent ring to use external light from the sides.
it should be on peak-site. I have it with the leather bag.

 

[TheToadMen]

Will do later: Its called PEAK Scale Lupe 10x (Lupe is german). it has a transparent ring to use external light from the sides.
it should be on peak-site. I have it with the leather bag.

You mean this PEAK Lupe?

 

[europanorama]

yes thats exactly mine.
http://www.peakoptics.com/index.php?main_page=page&id=1
reticles no 1(PS-1-M titled)-see also the two vertical line scales!
i could verify my pinhole being approx. 0.45mm. Its 0.455 measured from image.