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View Poll Results: Is it possible to do any better than this using the tools I used?

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  • No, not really.

    1 20.00%
  • Yes, but it won't really improve image quality enough to matter.

    1 20.00%
  • Yes, and a rounder, smoother hole with sharper sides would improve image quality.

    3 60.00%
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  1. #1

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    2nd pinhole attempt!

    Here's my 2nd pinhole drilling attempt. I think I actually had the hole rounder than this but I managed to screw up the burnishing at one point by letting the needle go too far in and tilt sideways. Anyway, here are the parameters I'm going on based on mrpinhole using 4.25" x 3.25" (polaroid pack film dimensions):

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    I cut a square out of a soda can using a box cutter. I tried to flatten it out by rolling it against things of various diameters but didn't do such a good job. Hopefully I got it flat enough. I then sanded off the silkscreening on the label side of the aluminum and attempted to "dimple" it with a rather blunt sewing needle. Not sure if the needle I used was still too sharp, or if the cardboard I was using was too soft but I didn't do that good of a job with the dimpling.

    I set my ancient, somewhat beat up, 1920s micrometer to 0.019" and stuck the thinnest needle I have into it. It didn't go in that far, so I put the needle in the chuck of my Dremel tool and lathed it against some 1500 grain sandpaper (which worked on it very slowly). I measured it now and then to see when enough of it had been tapered to my satisfaction. I then stuck it into the micrometer and marked the spot where it stopped with a sharpie. I decided that wasn't good enough though, and not having a pin vise at this time I put the pin in my dremel again, loosened the chuck so it would slide a bit, then stuck it into the micrometer gap so that the smallest part that wouldn't fit was right up against the chuck.

    So then I just used the Dremel like a pin vise, without turning it on, to poke a hole in my not-so-deep dimple.

    I then sanded both sides with both 600 and 1500 grain sandpaper. (The 1500 was going frustratingly slow, maybe due to my less than sharp and deep dimple.)

    Then I decided that was still going too slow so I decided to try experimenting with a grinding stone on the dremel to see what I could do. It wasn't a disaster but it probably wasn't the best idea.

    I also tried using the polishing wheel on the dremel with some abrasive compound (jeweler's rouge, basically) and that seemed to be ok but the surface was still a bit uneven. Not sure if the grindstone screwed it up or if I just didn't get the aluminum square all that flat.

    Looked at it with my standard 10x jeweler's loupe, saw some burrs, and burnished it with my lathed-down needle. Repeated the sanding and burnishing a couple of times, but the last time I did the burnishing I did a rather sloppy job. (All the burnishing was done just holding the needle by hand without using a pin vise or using the dremel like a pin vise. I just used the makeshift pin vise technique to punch the initial hole.)

    At some point I got tired of messing with it further, and in the loupe it looked pretty good. So I stopped.

    Here are photos that I took of it using my iPhone with a 10x loupe held in front of the lens. (Yea, that actually works.) I don't have a scanner handy at the moment. All of the photos are a bit oversharpened to enhance detail at the expense of aesthetics.

    xxxxxxxx
    The photo above shows the pinhole with a ruler. That's the metric side of a cheapo wooden ruler showing mm.


    Click image for larger version. 

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    The one above shows the lathed-down needle next to the pinhole with the part of the needle that the micrometer says is the right width right next to the hole. It's very faint but there's a little sharpie mark on the pin at that point. NOTE: the needle is not actually bent. Since it's not exactly photographic grade glass, the loupe isn't corrected for astigmatism and thus exhibits a good bit of barrel distortion.

    Click image for larger version. 

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    That's my attempt to compare the hole to the micrometer gap. Of course the shaft of light shining between the gap isn't the actual size of the gap, which is pretty difficult to see, and the lighting and DoF are horrible, but I gave it a shot anyway.

    Click image for larger version. 

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    That's the pin placed over the hole. Difficult to tell, but maybe the hole is actually a little narrower than it looks. The mark on the pin is the sharpie mark showing the part that wouldn't go into the micrometer gap. (That part of the pin should be a little too wide anyway, so shrug.)


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    These two are my attempts to photo light shining through the hole. I think in the one on the left I just held it up toward the room lighting, and in the one on the right I placed a paper towel on top of a flashlight (to act as a diffuser) then set the pinhole plate on top of the paper towel and photographed it.

    Not sure but perhaps these might be the photos that best show the real shape of the pinhole.

    Anyway, I'm thinking that this isn't too bad but I'm betting I could actually do a little better next time.

    What do people think? Is it possible to do better, and is doing any better beyond this worth anything in image quality terms?

  2. #2
    SMBooth's Avatar
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    Put it in your camera and take some photos....

  3. #3

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    Ok, here's the camera and first photo

    Here's the camera I made using the Tektronix C-50 series Polaroid pack film back:

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    I took this brass light stand adapter stud thing, drilled some holes in the film holder, then bolted it onto the holder using a 5/8" bolt and some washers to distribute the force. The other side on the adapter is a standard 1/4-20 tripod hole so it bolts on nicely to the arca-swiss compatible plate that came with the ball head for my Gorillapod. I glued that wide fender washer to the tripod side of the stud with some silicone glue. It should help distribute the force on tripod plates, stabilizing the camera more and avoiding damage to tripod plates that don't deal well with the small base of the stud.

    The Polaroid back also has a slot for a darkslide, but the actual darkslide was missing. So I made a new one using, guess what? The metal front plate from an old metal Polaroid cartridge! Though the darkslide was no doubt originally intended to allow you to switch backs on your osciliscope camera without exposing the film, I decided that I'd just use it as a shutter for the pinhole for now.

    I used the Gorillapod because my real tripod is sort of occupied at the moment. Then I just created a really simplistic test photo setup like this and tried to align the camera best I could:

    Click image for larger version. 

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    The pinhole is supposed to be f/276 and since my light meter only lets you set it no smaller than f/90, it seems that I essentially have to divide the film's ISO by 10 (how convenient) in this case and use that as the ISO in the light meter. Since I don't want to wait forever for this low light photo I put some Fuji FP-3000B in the thing.

    The light meter said something like 2.6m and I had to guess at the reciprocity failure for such a long exposure. I guessed +3 stops, so I estimated the exposure at about 20 minutes. Looks like I guessed right on the first try. Here's the whole print from the shot, "scanned" using a "scanner" iPhone application (one of those ones that corrects for perspective distortion etc):

    Click image for larger version. 

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    That's with no adjustments other than the scanner app's guess at the correct contrast.

    I'm pretty happy with that, expect that I'm wondering where the heck that black line came from. It seems like something was covering the negative the whole time, somehow. I'm wondering if it just got misaligned in the cartridge or something when I pulled the masking paper out of the new film pack. I can't really think of anything else that might cause it except maybe I didn't fully push the film pack in or something, or it's a random film alignment problem. I guess I'll just see if this keeps happening.

    Now I just need the sun to come up so I can take some real photos!

  4. #4
    Joe VanCleave's Avatar
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    Of course, pinhole photography images are always going to be softer than refractive lens images, and while "embrace the softness" might therefore be a good working philosophy there's nothing wrong with attempting to eek out as much resolution as possible from your pinhole system.

    Pinhole size and quality is only one factor affecting overall resolution, another major factor being format size. For equal angles of view, a larger film format will require a longer focal length and thus (by Rayleigh's formula) a commensurately larger focal ratio, which will produce images less affected by diffraction. There is also the advantage afforded by larger film formats of needing less enlargement, further reducing image degradation.

    But if you're going to find the optimal pinhole, and don't want to purchase commercial electron microscope apertures (which are the best one can find) then do yourself a favor and choose a material a bit better suited than soda can metal. You want to make your pinhole as close as possible to a two-dimensional hole, not a three-dimensional tunnel. The more tunnel-like your pinhole, the more off-axis vignetting and loss of resolution, especially if you are after wider angles of view.

    I might also mention that a sturdy tripod is also very important to sharp images, more so than with glass-lensed LF cameras, since your typical pinhole exposure time will be much longer. Another important thing with these long tripod-mounted exposures is not moving your feet anywhere near the tripod during the exposure, especially on soft ground where such movement can slowly but perceptibly move the camera.

    Wind-induced camera movement is also an important image degradation factor, a good reason to have both a heavy tripod and heavy (like plywood) camera that can't easily shake in the wind. In this regard, adapting a bellows fitted LF camera for pinhole is probably the worst idea as far as image sharpness in real-world wind conditions. Making a solidly overbuilt MDF or plywood box camera is better, plus you will come to learn to appreciate the camera as a hand-built crafted thing.

    Another equally important factor is the shape and roundness of the hole. Uniformity and smoothness can only come through lots of practice making pinholes, which you should do before settling on a final version.

    Of course, they all will form an image, it's really a matter of how good of an image will you achieve.

    I therefore recommend thin brass sheet metal, no thicker than 2 mil, and use the dimple-and-sand method, using fine emory or a wet stone to sand the tip of the dimple down to ultra-thinness, then barely pierce with the tip of a needle, then continue to sand and ream out the hole until you have the correct diameter and a smooth, clean aperture. With this method I inspect periodically using a loupe, and measure the diameter with the pinhole placed adjacent to the edge of a machinist's scale, marked in millimeters, with the aperture half exposed at its widest point and sufficiently backlit for proper viewing; you can easily estimate the pinhole diameter to within a quarter of a millimeter using this method. You need to practice this method on a dozen or so pinholes until you arrive at the cleanest, roundest, thinnest hole of the correct size for your camera's focal length.

    Regarding film, though panchromatic sheet film yields shorter exposure times, don't discount the use of paper negatives, especially graded paper whose image contrast is less affected by the color of the light than with multi grade paper. There's also a theoretically sharper image possible with paper, due to it being sensitive to light of a wavelength shorter and narrower in spectrum than panchromatic film; though in practice you will lose this added sharpness if contact printing your paper negatives.

    Like with everything else, there's a science to deriving the best possible results. But it's also possible to over analyze the details. My best advice is to shoot a lot of film or paper as you go along, because experience can teach you much, plus you won't be burdened as much by the prima donnas who eschew the primitive pinhole camera as something they did in school as a kid, but now they're beyond that. You will find through experience that there are only a few things that can truly improve the sharpness of your images (or, more exactly, prevent further degradation), and that also having a powerful artistic vision to you work is at least as important to the audience as is sharpness, which is often over-rated. In this regard, studying the work of other pinhole photographers can give you much inspiration creatively.

    -Joe
    Last edited by Joe VanCleave; 07-09-2012 at 07:23 AM. Click to view previous post history.

  5. #5
    Joe VanCleave's Avatar
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    Regarding long exposures under dim lighting, you will find that under certain circumstances, like for instance dimly lit daylight, that paper negatives can provide shorter exposure times than sheet film, due to paper's lack of reciprocity failure.

    Conversely, working under artificial lighting with sheet film is typically better, due to paper's lack of sensitivity to the longer wavelengths. Since I work almost exclusively with graded paper negatives, my still - life work is done in the daytime using indirect north-facing window light, which at least is of a color usable for paper.

    -Joe

  6. #6

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    Thanks for all the good advice here.

    Quote Originally Posted by Joe VanCleave View Post
    Of course, pinhole photography images are always going to be softer than refractive lens images, and while "embrace the softness" might therefore be a good working philosophy there's nothing wrong with attempting to eek out as much resolution as possible from your pinhole system.
    Like you say, I'm not aesthetically antithetical to softness, but I also like to push the envelope on technical things like this just to see what can be done. Similarly, I don't have a religious preference for film vs. digital.

    Pinhole size and quality is only one factor affecting overall resolution, another major factor being format size. For equal angles of view, a larger film format will require a longer focal length and thus (by Rayleigh's formula) a commensurately larger focal ratio, which will produce images less affected by diffraction. There is also the advantage afforded by larger film formats of needing less enlargement, further reducing image degradation.
    So given that I'm using 4.25x3.25" film, does the mrpinhole calculation of 136mm and 0.49mm seem optimal? From reading something elsewhere, I seem to remember that his calculator's assumption of ideal is "maximum sharpness" vs. "maximum resolution". This actually has me wondering if it would be better in both softness and sharpness terms to optimize for resolution and then use sharpening algorithms after scanning if sharpness is that important. (In other words, will "better resolution" images sharpen better digitally while being higher resolution than "better sharpness" images would be in terms of both?)

    But if you're going to find the optimal pinhole, and don't want to purchase commercial electron microscope apertures (which are the best one can find) then do yourself a favor and choose a material a bit better suited than soda can metal. You want to make your pinhole as close as possible to a two-dimensional hole, not a three-dimensional tunnel. The more tunnel-like your pinhole, the more off-axis vignetting and loss of resolution, especially if you are after wider angles of view.
    I've thought about just buying electron microscope apertures, but I figured that I'd try doing this myself first. I'll see if I can find some suitable brass. (Wonder if the hardware store has brass stock that thin?)

    Speaking of film and long exposures, it kind of seems like this Fuji FP-3000B stuff has a pretty bad tone curve for long exposures. The chart in the following photos, when photographed using a Mamiya 645 using the same FP-3000B film with a polaroid back and relatively "normal" exposure times, will show a clear difference between all of the patches when the middle gray one (big patch in the middle) is exposed properly. Each of these patches is +/- 1/6th EV from the ones next to it.

    However the same chart photographed with my pinhole using the same FP-3000B with a 30 second exposure (the light meter said 15s and I added a stop for reciprocity failure) looks like this:

    Click image for larger version. 

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    (I had the camera on a little tripod on the carpet and was sitting and moving around a foot or two away, so I wasn't exactly expecting sharpness here, just an exposure test.)

    Then again maybe this particular film is just more sensitive to development time than the FP-100C. (It's actually supposed to be 15s for 80F rather than 30s.) Fuji's newer films are supposed to have "self terminating" chemistry or something, but I haven't really looked at it carefully with the FP-3000B. Anyway, to me a lot of these patches don't look very distinct. (They seem to look more distinct in this cropped but otherwise unmodified photo of the print, but something in the iPhone OS might be applying some sort of adaptive tone curve when processing the sensor raw or something.)

  7. #7

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    Because they don't fit the Dremel that well consider going to your dentist. The round burs he/she will have are of specific diameters and are usually tungsten-carbide which should handle your metal. Also consider contacting a dental lab that may have a milling machine or drill press that handles those burs.

    http://www.jeffreyglasser.com/

  8. #8
    Jim Jones's Avatar
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    Quote Originally Posted by aterimagery View Post
    . . . does the mrpinhole calculation of 136mm and 0.49mm seem optimal? . . .
    Optimal pinhole diameter is a matter of taste, like seasoning on food. I prefer Pinhole Designer with a user constant of 1.4 when determining pinhole size. This yields a diameter of .383 for a 136mm focal length on film. This choice is based on many resolution tests. Some adjustment of the diameter for pictorial photography might suit others better. The shorter the focal length (and thus the smaller the pinhole) the sharper the image. Pinhole cameras are more suited to wide angle photography than normal or longer focal lengths. Larger pinhole cameras can record more detail for a given angle of coverage. There is a wealth of information on http://www.f295.org/Pinholeforum/forum/Blah.pl

    Hardware stores sell brass shim stock in thickness from .001 inch up. .002" is a good comprovise between thinness and ease of working. A few dollars spent on brass shim stock should last a lifetime.

  9. #9
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    You can do a lot of testing, and photograph charts and such, but until you get out there and actually expose some film, using the pinhole as intended, you will never know whether you'll be satisfied or not.
    I have seen pinhole photographs that I could have sworn were photographed with a lens; that's how sharp they were. But then again, what's the point of using a slow and impractical pinhole?
    My own experience with pinhole is with a simple Zero Image 2000 medium format pinhole camera. It doesn't have the absolutely best pinhole in the world, but it's good enough to make 14" square prints from 6x6 negatives, where if enough attention is paid to the printing values, contrast, toning, etc, sharpness isn't really an impediment.

    Have fun!
    "Often moments come looking for us". - Robert Frank

    "Make good art!" - Neil Gaiman

    "...the heart and mind are the true lens of the camera". - Yousuf Karsh

  10. #10

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    My dentists (two married to each other) like me so I bet they'd give me some old drill bits to mess with. I've got the Dremel variable diameter chuck so hopefully that would work for holding them.

    I went to the local Lowes and asked the hardware guy for brass shim stock. He claimed they didn't have any. I don't think he knew what shim stock was. I got out my phone and looked it up on their web site, and found one entry for a 4x5" 0.01" thick sheet. After pointing this out to the hardware clerk he said something like "oh yea, we have that over here. I thought you wanted a BIG sheet of brass." Eh, ok. I believe I told him I only needed a small amount. Apparently it also didn't occur to him to tell me about what they did have just on the off chance that it was sufficient. Probably the best place to go would have been this chain of hobby stores in the area, but they went out of business. I'll have to try a less mass-market hardware store in my area. (I was going to Lowes anyway to return something, and would have been surprised if they'd had 0.002mm brass.)

    This small brass sheet was something like US$4.50 and was in a drawer with "hobby" type parts... not in the rack with the usual welding stock, metal strips, rods, rebar, etc. It's a bit thick but I intend to experiment with using my dremel with the drill press type holder I have anyway, so thickness may not matter too much if I can do most of the "sanding" with a power tool and then polish up the crudeness with sandpaper.

    I also bought a tin sheet of the same size because it was a little thinner and only like $2, so I figured it might be worth experimenting with. It's probably too soft for pinhole-making but I figure I might try it anyway and it'll come in handy for something regardless.

    I wanted to make some fuzzy photos yesterday so I drilled my painstakingly made 0.49mm hole out to about 0.8mm (1/32") with a common drill bit in about 2 seconds without even deburring it. I'm planning to make another more precise pinhole with the brass anyway, so I didn't really care about mangling it. (Yea, the photos were fuzzy enough though I don't think the f number is really what it should be for 0.8mm at this focal length. Probably the fault of the tunnel-like hole and the burrs.)

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