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Pinholethrowaway
1-May-2019, 12:04
Hey LFP forum,

A friend just gave me his old pinhole camera. I'm not sure what his Aperture is on it. I'd like to shoot hp5 400 pushed at 640. Here are the camera stats, it's all I know about it:

Lens says .018" wide-angle 8x10, but he built it inside a 4x5 box.
The lens sits approximately 5 inches away from the film plane.

I'd love to know the Aperture of this LF pinhole camera so I could properly expose!!
Cheers

BrianShaw
1-May-2019, 12:09
Measure the aperture. I don’t think there’s really any other way to calculate the exposure.

tonyowen
1-May-2019, 12:17
Lens says .018" The lens sits approximately 5 inches away from the film plane.Cheers

Best guess is 0.5mm - which is a 'so called' standard pin-hole.
Next use the program 'Pin-Hole Designer' to give info on exposure etc
Regards
Tony

Oren Grad
1-May-2019, 12:17
Based on the labeling, the opening is presumably .018", or approximately 0.46mm. With a "focal length" of 5 inches (127mm), that makes an f/stop of about 276.

Pere Casals
1-May-2019, 14:23
You also may take a set of sewing needles, find one that passes and one that does not pass, than take a digital caliper to measure the neddles.

The calculator will tell you the aperture: https://www.mrpinhole.com/calcpinh.php

Anyway you may make a bracketing by removing the slide of the film holder in several steps during exposure, like if it was a test strip under the enlarger, just guess an f/ for the band in the middle, and find what under/over exposure is the right one for the f/ you guessed.

I did that to find the ISO for paper negatives...

Pinholethrowaway
2-May-2019, 02:28
Hey everyone, I just wanted to say thank you for all the wonderful responses!!!! :)

I can't wait to use this camera now!!

Jim Jones
2-May-2019, 08:38
Best guess is 0.5mm - which is a 'so called' standard pin-hole.
Next use the program 'Pin-Hole Designer' to give info on exposure etc
Regards
Tony

Rather than use a "standard" pinhole, the best pinhole diameter should be calculated for the intended focal length. This gives a noticeable improvement in sharpness over a more randomly selected diameter. Experience has taught me to use www.pinhole.cz/en/pinholedesigner with a user constant of about 1.5, although a somewhat larger constant may be better for ultra wide angle use. If the pinhole can be laid on a flat bed scanner and scanned at the minimum exposure that gives good clean edges, the pixels across the pinhole can be counted and the diameter accurately calculated. Overexposure gives an enlarged apparent diameter.

Chauncey Walden
3-May-2019, 15:13
If that size (,018 inch) is correct with your HP5 rated at 640 in bright sun I would try 1/2, 1 and 1.5 second exposures.

Tin Can
3-May-2019, 16:14
Jim,

Do you think this program is safe to install?

I just stopped the install as WIN 10 gave a warning.

Is that program significantly better than the online, http://www.mrpinhole.com/calcpinh.php which I used a few times.

I don't know what the 'constant' means as Mr Pinhole does not use that term.


Rather than use a "standard" pinhole, the best pinhole diameter should be calculated for the intended focal length. This gives a noticeable improvement in sharpness over a more randomly selected diameter. Experience has taught me to use www.pinhole.cz/en/pinholedesigner with a user constant of about 1.5, although a somewhat larger constant may be better for ultra wide angle use. If the pinhole can be laid on a flat bed scanner and scanned at the minimum exposure that gives good clean edges, the pixels across the pinhole can be counted and the diameter accurately calculated. Overexposure gives an enlarged apparent diameter.

Jim Jones
4-May-2019, 05:17
As I recall, Pinhole Designer can be downloaded from several sites. I've used it for a long time with never a problem with the download, but don't remember which site I downloaded from. The 'constant' in Pinhole Designer is a variable that lets the advanced pinhole maker to tailor the calculation to his own preference. The Rayleigh constant of 1.9 seems a little large to me, although a good compromise for wide angle cameras. I use about 1.4 or 1.5 for slightly sharper image centers.

tonyowen
4-May-2019, 05:36
As I recall, Pinhole Designer can be downloaded from several sites. I've used it for a long time with never a problem with the download, but don't remember which site I downloaded from.

Before I posted this reply I googled pinhole designer and was offered version 2.0. [for both windows and mac]
My program - running on win7 - is version 2 and it's hyper-link is http://www.pinhole.cz

As Jim Jones says there are many variables, but the KISS principle applies for testing.

regards
Tony

Tin Can
4-May-2019, 05:38
I found this explanation.

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/Raylei.html

My takeaway is sufficient light as controlled by aperture, apparent aperture and bellows extension.

A concept that may be tested with a set diameter pinhole by varying distance to capture sensor.

Mr Pinhole helps define image circle.

I will not install Pinhole Designer.

tonyowen
4-May-2019, 07:06
Mr Pinhole helps define image circle. I will not install Pinhole Designer.

Its personal choice.
I found Mr Pinhole too complex and required too many variables to be entered before an answer is displayed.
By contrast, Pinhole Designer can be setup with just the chosen/assumed/estimated pinhole diameter and the chosen/assumed/estimated focal length/bellows extension, and the scene exposure reading at f22.
For the OPs setup Pinhole Designer gives f287 and a exposure index of 159.7 at f22

However, neither program is more right or wrong - just different

Regards
Tony

Jim Jones
4-May-2019, 18:26
We should keep in mind that Lord Rayleigh was perhaps more of a scientist and mathematician than a photographer, and therefore inclined to create formulae that would communicate concrete data rather than nebular diffraction limited pinhole photographs to his fellow scientists and mathematicians. Even experts on optics sometimes rely on theory rather than on experimenting when it comes to talking about pinhole imagery. For example, C. B. Neblette in Photography: its principles and practices (3 ed., 1938) stated that it was impossible for a pinhole to resolve line pairs in a chart like the popular Air Force chart if the pinhole diameter is smaller than the line pair spacing. Obviously he hadn't tested this. Diffraction usually degrades camera images at small apertures, However, a pinhole that has a diameter close to the size usually recommended for sharp pinhole photography can actually increase resolution above what basic theory claims. So, in addition to the term, "diffraction limited" we now have a term, "diffraction enhanced." Some LFPF member who is also a student of optics or photography is welcome to take this idea and write a dissertation on it. Beware, the phenomena may be masked when image forming is cluttered up by adding lenses.

tonyowen
5-May-2019, 00:45
For completeness I've attached three screen dumps of Pinhole Designer program with the OPs info.
On the second one I've chosen a film from a dropdown list
190955 190956 190957

regards
Tony

Jim Jones
5-May-2019, 06:26
Wow, Tony. although I've used Pinhole Designer for decades, I'd never thought to look at some of those features. Some of the information they contain is intuitive, some already familiar through experience. The program is still my favorite because some of the others assume the user lacks the experience or the inquisitive nature to explore the potential of pinhole photography on his own.

Tin Can
5-May-2019, 06:36
Both programs posted here do very similar things.

I simply prefer an online version.

More accessible and my computer is less at risk.

Google also says the the CZ site is 'Not Secure'.

So both Win 10 and Google are saying don't download...

Jim Jones
5-May-2019, 19:07
I just now downloaded Pinhole Designer, and Kaspersky didn't flag it then or in a quick scan afterwards. However, two out of three is more convincing.

pepeguitarra
5-May-2019, 19:23
As a reference, this is the 8x10 pinhole camera I built:

https://live.staticflickr.com/890/41469589422_9f8570ff40_c.jpg (https://flic.kr/p/26bwua5)20180416_200336 (https://flic.kr/p/26bwua5) by Palenquero Photography (https://www.flickr.com/photos/palenquero/), on Flickr