Designing my pinhole camera [beginner]

ilona · Apr 22, 2005

Hi all!

I'm seriously thinking of building my own pinhole camera. However, I'm an absolute beginner, so I feel I need some advice...

I'd like to go for a film camera taking 120 rolls. I had a look at the camera wizard at mrpinhole.com and I got the following values: focal 45mm; pinhole 0.28mm; f stop 159; angle of view 86.7. So, as far as I understand, I have to make sure that the film is at 45mm from the hole... Do these values seem correct?

Also, I need some knobs to advance the film, but I'm wondering how I'll be able to know how much I'll need to advance the film if I don't want the views to overlap. Any hint on how you are doing that guys???

Ed Sukach · Apr 22, 2005

I'm not sure why you chose a focal length of 45mm ..? That would be equal to a 45mm - wide angle lens for a 6x6 or 6x7 format. The limiting factor here would be "coverage" - with a 45mm focal length that would be 86.4mm (roughly - there usually is a large amount of "fall-off" - uneven exposure at the extremes of the frame) and 6x7 would probably be the largest acceptable format.

If you choose a longer focal length, the optimal pinhole diameter will be larger, and the circle of coverage larger - and the "angle of view" smaller... as it would be with a conventional lens.

"Mr. Pinhole" is a good, useful program. I would also suggest "Pinhole Designer" available from
[ http://www.pinhole.cz ]. LOTS of good information there... also, mention of a "Pinhole Enlarger ..."!!!

Film advance and framing is a problem. Many will "savage" a camera by removing its lens and substituting a pinhole, either through a "body cap" or with a cardboard/ paper mache', -- I don't know -- silly putty - jury rig.
I'm in the process of building a pinhole camera right now ... using a metal Maxwell House coffee can as a body. I'm not going to worry about precise framing - I'll just cut a length of film and tape it to the bottom of the can.
Should give me a focal length of 6" and an aperture of f/300, with a pinhole diameter of 0.020"

BTW..., WELCOME!! to APUG.

.

ElrodCod · Apr 23, 2005

ilona said:
Hi all!

I'm seriously thinking of building my own pinhole camera. However, I'm an absolute beginner, so I feel I need some advice...

I'd like to go for a film camera taking 120 rolls. I had a look at the camera wizard at mrpinhole.com and I got the following values: focal 45mm; pinhole 0.28mm; f stop 159; angle of view 86.7. So, as far as I understand, I have to make sure that the film is at 45mm from the hole... Do these values seem correct?

Also, I need some knobs to advance the film, but I'm wondering how I'll be able to know how much I'll need to advance the film if I don't want the views to overlap. Any hint on how you are doing that guys???

ilona,
Take a look at this link. There are a couple of ideas for your project. I've made two 6X9 format cameras for 120. One is 80mm & the other is 57mm; both would be considered wide angle for that format. If you're going to process the film yourself the format choice is wide open but for lab processing I'd go with 4.5x6, 6x6, or 6x7.
There's another (there was a url link here which no longer exists) here on a similar topic.

grahamp · Apr 23, 2005

I have a Zero Image 6x4.5/6x6/6x9 pinhole camera with a 'focal length' around the one being discussed (40mm). With a good pinhole the fall off on monochrome negative is negligable. It is very wide - something like a 20mm on 35mm format - aperture around f/235. I have some results here: Dead Link Removed
Film was Delta 400.

Using 120 film means that film advance is done using a red window to look at the frame marks on the backing sheet. If you make a camera capable of 6x9, you can set internal masks to work smaller.

Zero Image is at http://www.zeroimage.com/

k_jupiter · Apr 25, 2005

Well, the easiest way to do this is to modify an existing 120 camera, either a folder or, as I did, a camera with a lens that pops out on a tube. If the shutter is still working, all you do is replace the lens with your pinhole medium, sheet brass or the like. The aperture is approximately the aperture of the lens you replaced, i.e. 75/80mm for 6x6 or 105 for 6x9. If you take your time, use the correct methods for making your pinhole, you will be amazed at th clarity of the images you get out of this type of camera. The spacing is done through existing red panl holes on the back of the caamera.

tim in san jose

ilona · Apr 25, 2005

Hi!

Thank you all for your useful tips and links!

As far as I understand, the 45mm is actually a bit wide for 120 film; that is to get a good image quality over the whole surface of the film. (I didn't really choose 45mm, that's what mrpinhole.com gave me when I typed the film dimensions. But such a wide angle looked pretty nice at first sight.) So, the 'coverage' value is quite important it seems to make sure I get a constant image quality.

Also, the regularity of the hole will have an influence on the quality of the image at the edges, right? As I'm going to make the hole by hand (read: no precision tools here), I guess I'd better take a narrower angle and a larger coverage.

So for example, if I take 85mm as focal length, the coverage would be 163.2. That would produce an image that would be large enough for my film, right?

Also, I'm wondering what would be the diameter of the "useful" image for a given hole size. I mean: for a given hole size, there should be a circle in which the image is sufficiently good. And I expect the "edges" of the image diameter to be of less quality (blurred, lighter...).
Is there a formula to calculate that too?

ElrodCod · Apr 25, 2005

85mm will cover 6x9 format edge to edge. It's the equivilant of about a 35mm lens on a 35mm camera. You can buy a .014" jewelers drill bit and a pin vise at your local hobby shop for around $5-10. It will be about f/ 225. Go toPinhole Designer,it's a quick download and will calculate what you need.

Ed Sukach · Apr 25, 2005

Ilona-

If you check Mr. Pinhole, under Pinhole size calculator, the "Image circle diameter" is displayed when you enter the focal length. For 85 mm - the Image circle diameter will be 6.43" / 163mm, with a "best" pinhole diameter of 0.015". That should be easily sufficient to cover any 120-sized frame.

ilona · Apr 25, 2005

Thanks Ed! I didn't realize until I read your message that this 85mm film dimension was the diameter absolutely needed by the film. But of course, the diagonal is also the diameter...

However, my previous question was also about "what is a safe margin between the diameter absolutely needed by the film (or diagonal) and the diameter of the image produced by the hole (or coverage)": 1cm, 2cm, 4cm extra on each side???

So, indeed, I saw that the coverage would be 163.2 and would probably be sufficient taking 120 film. But I was more wondering about the quality of the image at the edges of the circle (coverage) and to what extend the quality is degrading (it seemed to be a problem with my 45mm tentative design where the film was barely covered by the pinhole image).

Actually, I'm just wondering how much I can safely decrease the focal length and still ensure a good image quality including in the corners.

Sorry if I wasn't that clear in my previous message (I hope this one helps!).

ilona · Apr 25, 2005

Actually, looks like it doesn't really make sense to go under 50mm focal length with 120 film (according to mrpinhole.com)...

Ed Sukach · Apr 25, 2005

ilona said:
Thanks Ed! I didn't realize until I read your message that this 85mm film dimension was the diameter absolutely needed by the film. But of course, the diagonal is also the diameter...

You lost me here. The diagonal of a "6cm x 6cm" (actually a lot closer to 5cm x 5cm ... measured it) frame is about 70mm and that would be the necessary image circle. An 85mm focal length, with an image circle of 163mm is considerably more than necessary. OK to have more than you need, not good - at all - to have less.

However, my previous question was also about "what is a safe margin between the diameter absolutely needed by the film (or diagonal) and the diameter of the image produced by the hole (or coverage)": 1cm, 2cm, 4cm extra on each side???

I don't have an answer to that. It depends on how much "fall-out" (dimness at the extremes of the frame) you consider to be acceptable. Some will tolerate - or even WANT more than others.

I can only suggest that you try it - and see what happens - which is pretty much what is necessary in pinhole photography anyway.

ElrodCod · Apr 25, 2005

Ilona,
This image was taken with my 80mm rollfilm pinhole camera. The lab cropped the sides a bit to make a 4x5 print but the negative doesn't show any fall off. The 57mm camera works just as well. I'm sure that if your camera's "focal length" falls within the two you'll be satisfied with the coverage. I'm planning on building a new camera as wide as the physical limits allow. The diameter of the film spool is about an inch; plus 1/8" for clearance makes it in the 30 to 35mm range. If there's fall off.....who cares? It's a pinhole camera.

ilona · Apr 26, 2005

I'm going to give that 85mmm focal length a try and we'll see! As you said, it's pinhole photography ;-)
I'll be curious to get news about your new camera, ElrodCod. You'll post updates in the forum, I guess.

Thank you all for your useful tips and input!!!

Donald Qualls · Apr 26, 2005

FWIW, I've seen pinhole images done on 8x10 film with a focal length under 30 mm, which cover the whole frame (albeit with light fall-off in the corners like a Holga, but still printable and with detail recorded over the whole frame). The field of view limitation for a well-made pinhole is more likely to be from vignetting by parts of the camera than by light fall-off; most negative film will let you overexpose the center by one to two stops, and underexpose the edge by one stop, and still produce an image that just needs a little dodging and burning; with reduced EI, low-contrast development, darkroom manipulation and the right film (like 400TX), you can get away with still one more stop of difference, which would be equivalent to a 4:1 path length difference between center and corners of the frame.

On 6x9 cm, you could probably get away with a 35 mm pinhole, if the camera were carefully made to avoid vignetting. 45 mm isn't at all uncommon, and though the exposure will vary too much over the 6x9 frame for slide film, not many folks shoot 6x9 slides anyway.

ElrodCod · Apr 26, 2005

I agree with Donald. I've read (can't remember where) that the image circle formed by a pinhole is three and a half times the focal length. The image circle calculator on the Mr.Pinhole site uses a factor of 1.92 which, IMO, is quite conservative.

ilona · Apr 26, 2005

Indeed, I noticed that the results given by mrpinhole.com and the Pinhole Designer software were quite different.

ilona · Apr 27, 2005

I found another calculator on the web: http://www.stanford.edu/~cpatton/pinhole/calculators.htm (for Windows).

I didn't try it yet.

ElrodCod · Apr 27, 2005

ilona said:
I found another calculator on the web: http://www.stanford.edu/~cpatton/pinhole/calculators.htm (for Windows).

I didn't try it yet.

I have that one too but I don't find it as useful or as easy to use as the Pinhole Designer.

Designing my pinhole camera [beginner]

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