Just made a pinhole camera! Have a few questions.

Okay. I made a very simple pinhole camera. Am I right in thinking that a smaller hole will make a sharper image? I didn't find the smallest needle I have so will search for a real tiny one!

The negatives were really light so I'll have to leave the pinhole open longer?

Fun to make. I think that this will be a great project for my photography kids. I'll just have to practice a bit to make sure I can get a good image before I show them.

-Lori

To a point the smaller hole produces a sharper image, but eventually the sharpness becomes diffraction limited. Probably equally significant is the quality of the pinhole itself. A perfectly round, knife-edged hole is the best. Pushing a needle through something creates all sorts of turned and ragged edges. One classic method just uses the needle to raise a small pimple, then that is sanded off very carefully to open a hole. With that method, the needle diameter isn't particularly important.

There are some calculators and resource pages on the web you might find useful.

Sounds as though you need longer exposures. With some films, the reciprocity effects become extremely severe, needing 3 or 4 times (or more) exposure beyond what the exposure computed from the f-stop might predict.

It's fun stuff.

I've learnt to think of my pinhole images in terms of softness. It's like learning to see what will work in B&W. You can talk about pinholes and sharpness, it's all relative but not really worth the effort. I mean if you want sharp, use a lens. Pinhole excels at softness, you can have more or less softness but that is what you are working with. Accept the softness and you can start to consider the qualities of softness and what they offer. So the method described by DWThomas, sanding the pimple, gives a much sweeter quality than popping a hole into tinfoil. Actually, for sharpness you want to be using a laser. There are other variables to consider too, reciprocity is definitely a factor in pinhole but also there is a great difference between a paper negative and a film negative. It's all good. I think pinhole, zoneplates and the whole raft of lenseless photographic methods is a delight and I would only encourage you to do it.

Thanks everyone! It is a lot of fun! Something that was just a few pieces of cardboard and an aluminum can yesterday is a camera today! I'll try to just sand the dimple made by the pin. I sanded the hole after I made it but the hole is probably not perfectly round. I just love the look of pinhole photos. Mine were just extremely fuzzy. I think that I just need to keep it stiller! I already have 2 kids that want to make cameras for a project. Should be fun! We are just using paper so I just need to increase my time that the pinhole is open. Was my first contact print today too! Fun, Fun!

My matchbox PH's shoot at about f/90. Aperture can make a difference to a point. I think the quality in the hole edges make much more difference. If the light enters the camera through a smooth-edged hole it takes a more direct path to the film and creates a 'sharper image'. So I wouldn't worry too much about the size of the hole unless you want to know what aperture you're shooting at. But why make this thing technical, right? Kinda defeats the purpose, in my mind.

While your going to get information to your posted questions here, pop over to http://www.f295.org and go to the forums. Lot of information just waiting to be read. Good thing about PH is you can be as technical or non technical as you like and still get great and interesting results. But knowing something about the science helps get those images quicker, specially the relationship of pinhole diameter to f-stop for exposure calculations.

Ha ha! I'm glad I found this thread! I'm new to using (and making) a pinhole camera. This is what I ended up using for my pinhole camera :



And the "shutter" which is actually a magnet with a bit of paper on the back so it looks like a license plate :



Here's the image that I got from using Ilford Multigrade RC paper :



It's a bit...not exactly out of focus but extremely soft around the edges and missing some detail. (Not to mention the fact that it's way overexposed - my 3 seconds by counting one-one thousand, ect...).

I then enlarged the nail hole and placed behind it (inside the tin) a bit of black paper with a tiny tiny microscropic pinhole using on my old beading needles (I think it was a .3mm beading needle). This is what happened :



I did three tests just to make sure and they were all consistent.

I can't figure out why 1/2 of the negative is getting too much light but the upper 1/2 is fine. (That dark spot is where I accidentally dripped some Dektol on the paper before immersing it.) I took out the paper and enlarged the main hold just a bit more using a 2cm nail and in the body of the camera I placed a bit of heavy duty tin foil and resprayed the inside black.

I've not yet taken any more test photos yet. I'm just hoping that I fixed the issue with the 1/2 over(?) exposure. I'll load up the truck tomorrow and head out during my lunch hour and take a 1-2 second exposure (if bright) or a 3 second exposure if cloudy.

Here's a link for you: http://www.mrpinhole.com/calcpinh.php
With this, your exposures will be a little less guessing and a little more knowing. Photographic Paper can be assumed to have a sensitivity of about 5ASA.

Btw, I love your camera... everybody can take photos with an old shoe box, but using a little truck with the license plate as shutter? That's bordering on genius

Poking a hole directly into the metal will always give you such soft pictures. The smaller the hole, the sharper the picture (until a certain limit, see "optimal pinhole diameter") and your's was way too big and the edges are probably to uneven. The calculator can help finding out, what's best for your needs.
Using a small piece of aluminium foil or other very thin metal sheet is the usual practice for making small pinholes. Most people don't push the needle right through but use it to make a tiny dent which is then filed off. That way, you get very small and even holes. I usually just take a sewing needle, place it onto the aluminium foil with very little pressure and turn it around while placing my index finger on top (not pressing hard, just adding a little weight) and repeat that from the other side to smooth the rim... i can usually get almost perfectly round holes from 0,15 to 0,6mm in diameter that way.

As for your problem with the half-overexposed picture: It's either uneven developement (ruled out by multiple tests, I guess) or a light leak on the top of the camera, close to the film plane. Try putting a small flashlight into the box and taking it into a dark room. Does any light get out, apart from the pinhole? Then you've got a light leak that should be fixed with duct tape, a few drops of black paint or whatever you happen to have around.

I *almost* have the light leak fixed. *almost* I'm still trying to get the whole leak - and I'm using electricians tape right now. It seems to be working. The nail hole has a bit of tin foil behind it, covered for the most part, again, with electricians tape. *rolls eyes* My husband suggested duct tape but our local store doesn't carry any black duct tape. I made the pinhole with one of my sewing needles - so the picture is more clear and less soft looking. As for the uneven development, I tried out five tests and it did the same thing each time...so back to a very dark room with a flashlight! My kids think I'm nuts. (Wait...I am...but I'm not telling them that.)

As for the truck, thanks! I didn't realize I had it until I was cleaning out the basement one day.



There it is in the negative form - a 15 second exposure. I think some of that is just shadow from my front porch...and some of it may still be a light leak. I've another test or two to run just in case. The pinhole is still too big I think.



And a view of the newer, but still too big pinhole. :/ (That's one of my bjd's discovering the truck is now a camera. I've a photo shoot planned in the future of him taking a picture with it, me taking a picture with my old Brownie 2A and the two of us having our picture taken with my digital on a tripod!)

Thanks for the link and the reply! I appreciate all the help I can get because even though I took Photog. 101 in college (20 years ago), I'm just now getting back into my darkroom mode. I prefer working in darkroom (okay, the bathroom in the basement). No enlarger, yet. I'm hoping that maybe I can talk my husband into ordering one for me here in a few months.

Have you checked the f295 forum?

Ric Johnson said:

Have you checked the f295 forum?

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Yeah. I'm still waiting for approval.

I have one question, but it doesn't need a new thread. I metered f/22 4 sec. iso 5. After a lot of testing of different exposure times I ended up using 8 minutes exposure time when metering f/22 4 sec @iso5 to get a decent exposure. Is it correct that I need to calculate my exposre using about f/2800 iso5?

I read somewhere that the iso for paper is about 5, but it doesn't make sense when I needed 8 minutes exposuretime.

Grainy said:

I have one question, but it doesn't need a new thread. I metered f/22 4 sec. iso 5. After a lot of testing of different exposure times I ended up using 8 minutes exposure time when metering f/22 4 sec @iso5 to get a decent exposure. Is it correct that I need to calculate my exposre using about f/2800 iso5?

I read somewhere that the iso for paper is about 5, but it doesn't make sense when I needed 8 minutes exposuretime.

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Not sure I am reading the question correctly -- was this with a pinhole camera? Pinhole cameras typically have an aperture up around f/200 or smaller.

The typical way to deal with pinhole exposures is to make a chart using the shutter speed from a reading for f/22, then multiply it by a factor that relates the pinhole f-stop to f/22. For an actual pinhole aperture of f/220, the exposure relative to the exposure at f/22 would be the ratio of 220/22 squared (I made it easy for myself ) = 100. As such, a reading of 4 seconds would be multiplied by 100, 400 seconds, is 6 minutes, 40 seconds which is in the general order of magnitude of 8 minutes.

With film, these long exposures are affected by reciprocity failure, often quite drastically, as in requiring 3 or 4 times the metered length. For that one can make charts to include the reciprocity compensation. There is a Windows program called Pinhole Designer that can do some of these calculations and generate a chart for a number of films.

A little more detail about what you were actually doing might help.

DaveT

An enlarger is a good way to check your pinhole for hole size and roundness -- just put it in the negative carrier (cardboard and tape usually needed) and crank the head up to project a 10x or so image of the hole.

Pinhole focal length Vs negative size isn't something much talked about but is key to getting good results. The optimum is to use a focal length that is as short as possible while covering the media. Setting the focal length at 50% of the normal focal length is usually the limit. Naturally, at a wide angle the thinness of the pinhole is critical - the metal should come to a razor edge. Emery cloth should be used as the final abrasive to polish off the hole.

The bread truck camera, if it took 3x4" film (guessing at its size) would need a focal length of 2.5" or so; instead it looks as if it may be 6" - more suited to an 8x10 camera.

Using a long focal length is equivalent of blowing up the central 1/6 or so of the negative to make the final print - not a good thing when you are starting out at fuzzy.

Nicholas Lindan said:

The bread truck camera, if it took 3x4" film (guessing at its size) would need a focal length of 2.5" or so; instead it looks as if it may be 6" - more suited to an 8x10 camera.

Using a long focal length is equivalent of blowing up the central 1/6 or so of the negative to make the final print - not a good thing when you are starting out at fuzzy.

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It's a decorative tin - and the body where the pinhole and paper sits is about 3.5 inches long and the paper is around 2.5 inches wide and approx. 3 inches tall.

DWThomas: Yes it was with a pinhole camera, made out of a cardboard box. I metered with my normal lightmeter @iso5 f/22 so I would now how the light was, the reading was 4 seconds.

I used Ilford Multigrade RC IV deluxe as negative. ( developed in Agfa Neutol 1+9 for 1 minute)
Then I started out testing exposures, first 1 minute exposure, then 2 minute, then 4 minute and then 8 minutes. 1 and 2 minute was way too dark, 4 minutes I was getting there and 8 minutes was a maybe a minute too much. So 6 minutes 40 seconds like you suggest sounds perfect.

Do I understand you correct that if I use this method each time for this pinholecamera I can just multiply my lightmeter reading @iso5 f/22 with 100?

Regarding converting a meter reading to one's pinhole camera's f-stop:

(Fc/Fm)^2 * Tm = Tc

Where:
Fc = f-stop of camera
Fm = f-stop used on meter
Tm = exposure time recomended by meter
Tc = converted exposure time

In your example, Grainy, I didn't see where you gave us the f-number of the pinhole camera, but let's guess at a number like f/200. So here's the hypothetical calculation for the values you provided:
(200/22)^2 * 4 = 330 seconds, which is 5-1/2 minutes.

Provided that you keep using the F/22 reading on your light meter, and provided that the f-stop of your camera doesn't change, you can perform part of this calculation ahead of time, thus:
(200/22)^2 = 82.6

So, you would write down this multiplier of 82.6, take it with your camera, and multiply it by the meter reading (in seconds) to arrive at your corrected exposure time. Keep in mind that this formula does not account for reciprocity failure. In my experience, paper has very little issues, whereas film does.

NOTE 1: In the above example I assumed your camera's f-number was 200. You need to measure the diameter of your camera's pinhole, in millimeters, and divide that number into the camera's focal length, also in millimeters, to arrive at an accurate figure for your camera's actual f-number. Then, plug that number into the formula to get your actual working correction factor.

NOTE 2: I'm assuming that you're shooting paper negatives in daylight illuminated scenes. Remember that paper is, for the most part, only sensitive to UV and blue, and a very slight amount of green. Thus, if you meter an indoor scene that's illuminated by artificial lighting, the meter reading will not be accurate (because the meter's spectral response is much wider than the paper's), and you'll have to manually figure out how much extra exposure to use. For this reason, I recommend using panchromatic film (rather than paper) for artificially lit scenes.

NOTE 3: I've found that for using paper negatives you should try to be more exact with developer temperature and dilution (and freshness) than you might when using paper for prints. For instance, I use Freestyle's Arista brand grade 2 RC paper for negatives. I use Ilford's Universal paper developer, freshly mixed at a 1+15 dilution, and develop the negatives with the chemistry at 68f. That being said, once you start using the formula for converting your meter reading, and once your development process is consistent, then you should run a series of calibration tests to find out your paper's actual working exposure index; the value of "6" you provided may or may not be accurate.

To do these tests, mix up your chemistry at the proper dilution and temperature, in the daytime, and then shoot a series of exposures of a day lit outdoor scene that has a mix of shadows and highlights, using different exposure indexes for each shot. Start at about EI=2, working up to EI=12, making the calculation from the above formula for each shot. Write the metered exposure index on the back of each paper negative with a Sharpie marker. When you're done processing the negatives, you'll be able to review them and easily figure out the best exposed negative, and its corresponding exposure index.

Good luck, keep us posted.

~Joe

Grainy said:

....
Do I understand you correct that if I use this method each time for this pinholecamera I can just multiply my lightmeter reading @iso5 f/22 with 100?

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Assuming your f-stop equivalent is f/220, yes. But I was just guessing a typical number. Joe VanCleave in the post above has shown you the accurate way to do the math, and pointed out some possible pitfalls re: tungsten lighting. The smallest f-stop I can set on my Gossen Digisix is f/32, the meter has a ring you set and then read off combinations of shutter speed and f-stop. Using f/22 and a multiplier is just a handy way of extending that scale to the teeny tiny apertures.

In my first response at the beginning of this thread I posted two links that get you to a bunch of information about all sorts of pinhole considerations.

lorirfrommontana said:

Okay. I made a very simple pinhole camera. Am I right in thinking that a smaller hole will make a sharper image? I didn't find the smallest needle I have so will search for a real tiny one!

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Would a 0.4mm diameter hole be of any use to you ?

Thanks a lot for informative reply Joe. I will defently try this. I haven't measured the size of my pinhole yet because I don't have anything to measure it with. The only thing I know is that it's less than 1mm.

I uploaded a couple of test shots at my website:
http://www.sveino.no/blog/2011/02/11/lag-ditt-eget-pinholekamera-del-1/

For the nightshot I used 80 minutes exposure, the picture of the rock I exposed about 8 minutes. I don't know if it's possible to capture any more detail in the nightshot by increasing the exposuretime even more? It was complete darkness.

When I have time I will take more pictures and fine tune the exposures.

Grainy said:

I uploaded a couple of test shots at my website:
http://www.sveino.no/blog/2011/02/11/lag-ditt-eget-pinholekamera-del-1/

For the nightshot I used 80 minutes exposure, the picture of the rock I exposed about 8 minutes. I don't know if it's possible to capture any more detail in the nightshot by increasing the exposuretime even more? It was complete darkness.

When I have time I will take more pictures and fine tune the exposures.

Click to expand...

It's gorgeous. Beautiful.