Talk:Pinhole camera

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Calculating the f-stop & required exposure[edit]

"The f-stop of the camera may be calculated by dividing the diameter of the pinhole into the focal length of the camera" The f-stop is the aperture, isn't it? shouldn't it say exposure time? Shouldn't it be "focal length"/"diameter"="exposure time"?

The f-stop is not just the aperture size, but rather the ratio between aperture size and focal length, if I remember right. 128.163.235.175 (talk)

== DOF clarif

The article states: The depth of field is basically infinite, but this does not mean everything will definitely be in focus. Depending on the distance from the aperture to the film plane, the infinite depth of field means everything is either in or out of focus to the same degree.

It's not clear to me why infinite depth of field doesn't put everything in focus. The depth of field page did not help on this matter. Maybe I'm dense, but perhaps this article could explain this non-intuitive concept a bit more explicitly, at least as it applies to pinholes. --Ds13 03:03, 21 April 2006 (UTC)[reply]

A pinhole camera has a optimum distance between the pinhole and the imaging plane, which is the focal length. (Although that concept doesn't really make sense for pinhole cameras, as pinholes don't actually focus light.) All infinite depth of field means is that the focus is independent of distance (every distance is equally sharp), but the image can still be fuzzy if you deviate from the optimum distance (equally sharp does not imply sharp). --69.108.112.130 19:04, 9 November 2006 (UTC)[reply]

I'm pretty sure that a pinhole camera does not have an optimum distance between the pinhole and the imaging plane. As the imaging plane is moved further from the pinhole (i.e. "focal length" increased), the image gets larger, dimmer, and sharper. A user might choose an optimum image distance that suits their needs; say some distance where the image is both sharp enough for them and bright enough for them. But I don't think this is the same thing that the above commenter wanted to mean by optimal "focal length." I think user Ds13's question is a good one, and I'm going to delete the text that lead to the confusion. 128.163.235.175 (talk)

I think my earlier comment is basically wrong, and is perhaps disproved by the formula in this section of the article, that defines the optimal pinhole size in relationship to the "focal length" (distance from image plane to pinhole, in this case). I'm assuming that this formula gives the sharpest image? So that a larger pinhole increases blur due to plain old geometry, and a smaller pinhole increases blur due to diffraction? I still think that this part of the article is not as clear as it should be. If anyone agrees with me and knows how to improve it, go ahead; I'm not sure that I'll have the time to get to the bottom of this. 128.163.235.175 (talk) —Preceding comment was added at 16:18, 25 April 2008 (UTC)[reply]

I agree. Larger pinhole diameter will increase geometric blurring and decrease diffractive blurring. I found this page while investigating how those two effects work together, and I still haven't found a complete answer. There should be some reference in here about Airy disks, the Rayleigh Criterion, and the Circle of confusion. And the explanations could use some general clean up. The fact that the focal length is just the distance from the hole any image plane should be made prominent. I think the detailed mechanics of how a pin hole camera works should get a lot of attention in this article, since pinhole cameras are more interesting for demonstrating basic optics than they are as a practical camera. Pulu (talk) 22:12, 19 February 2009 (UTC)[reply]

External links[edit]

The external links section was far too big, especially for the size of the article. Several of the links seem to be providing the same info, just on different sites. I have put all the links below, so they can be hand-picked and put back into an external links section in the article. Even better, the information in them can be used to expand the article. That is where the information should be, not in an external link. Any links not required can be deleted from the list below. Please note: anyone connected with one of the sites below should not put it back into the links section. Tyrenius 01:09, 25 May 2006 (UTC)[reply]

World's largest camera - link broken[edit]

This link seems broken. Please could someone who knows a bit more about this area correct the link please? I spotted this one: http://www.legacyphotoproject.com/ which may be correct, but I'm not confident that this is the right link. Labour Lawyer (talk) 13:28, 25 May 2009 (UTC)[reply]

A Pinhole Photographer/Wolf Howard[edit]

Is it just me, or does the section about Wolf Howard's methods seem very specific? I mean, those are generic steps in the process - shouldn't the general process be reflected somewhere in the article in a more orderly fashion? The quote from him is good, but I just think that some of what is in that section should be made more generic (though I can't tell if there will be a consensus for that, so I won't touch it for now). Also, I'm going to upload a picture of some pinhole equipment later (a camera and basic developing tools) if there are no objections. Douglas Whitaker 02:29, 19 July 2006 (UTC)[reply]

Good point. I put this section in, as I thought it would be of interest to show a more detailed picture of the process in action. I've tweaked it a bit to try to bring this out. Let me know if you think it's still not right. Of course, what would be good would be to give another example or two, preferably showing a completely different approach to it.

You are of course free to edit and contribute and be bold! Just make sure any images have the right copyright tags or they'll get deleted. If you're not sure, leave a note on my talk page and tell me the basis on which the pictures are being provided.Tyrenius 02:55, 19 July 2006 (UTC)[reply]

I like the changes you made but went ahead and added another sentence to further make the process universal as well as a link to Fox Talbot. I'll work on getting a picture of the equipment later today. Douglas Whitaker 17:41, 19 July 2006 (UTC)[reply]

I've tidied that bit, but it's not quite right yet. Tyrenius 18:38, 19 July 2006 (UTC)[reply]

Yeah, I'll try and type something up a bit later (though I don't know in what direction yet). I also uploaded the photos I was talking about. I wasn't sure if I should zoom in farther on the one of just the pinhole camera to further draw attention to the pinhole, but I thought doing so might detract from how small the hole really is. --Douglas Whitaker 20:26, 19 July 2006 (UTC)[reply]

Maybe lighten the image, as it's a bit of a black lump on my screen? Tyrenius 14:45, 20 July 2006 (UTC)[reply]

Yeah, I agree. I'll take the garbage bag off from around the pinhole camera and retake the photograph. Though, it'll probably have to wait another day because my account is less than 4 days old and therefore can't overwrite any images. --Douglas Whitaker 16:09, 20 July 2006 (UTC)[reply]

Wait or just upload it with a different name. If you do that, just put {{db-author}} on the image page for the redundant one and it will get deleted. Is the garbage bag for blackout? In which case, you could have both images, to show how camera is blacked out. Tyrenius 18:09, 20 July 2006 (UTC)[reply]

I uploaded the new picture and changed the image descriptions to reflect the purpose of the black plastic. If any other pictures of pinhole camera related things (equipment, negatives, prints, etc) are needed, just let me know and I'll try and get them. --Douglas Whitaker 02:53, 24 July 2006 (UTC)[reply]

I think you probably know better than me. Tyrenius 03:17, 24 July 2006 (UTC)[reply]

Is this whole section not just a ploy to plug a book? The last paragraph reads like an advert to me. —Preceding unsigned comment added by 84.92.211.29 (talk) 22:45, 10 February 2008 (UTC)[reply]

No, that para was added onto the section later. I've removed it. Tyrenius (talk) 01:07, 11 February 2008 (UTC)[reply]

Black and White[edit]

I hadn't paid that close of attention to the introduction to this article, but the latest edit (The defect of pinholes are that the pictures come out in black and white if a CCD without color filters or a black and white film is used.) raises an interesting point: Isn't that like saying that "If you use black and white equipment, you'll get black and white photos"? To me, this doesn't seem like a defect but rather common sense. If I'm mistaken, please tell me. --Douglas Whitaker 17:54, 20 July 2006 (UTC)[reply]

Deleted till clarified. Tyrenius 18:04, 20 July 2006 (UTC)[reply]

Photo of Fire Hydrant[edit]

If I'm not mistaken, the positive should also be a mirror image of the negative and not just inverted colors. --Douglas Whitaker 20:49, 10 January 2007 (UTC)[reply]

Best to make certain (find references) first. Tyrenius 23:51, 10 January 2007 (UTC)[reply]

The scene was photographed directly on photo paper. This gives a photo with inverted colours, but the image is not reversed. (A little confusing, but the lens projects a rotated image on the surface of the paper. Only when looking through the lens or through a transparency is the negative image reversed.) To get the positive image, the original photo is placed (image side up) on an enlarger directly on unexposed photo paper. Using a rather long exposure time, the (still not reversed) image is exposed to the photo paper through the negative photo to produce an image with positive colors. I hope I've explained myself clearly. --Matthew Clemente 15:47, 12 January 2007 (UTC)[reply]

For example, take a standard 35mm negative. Looking at one side produces a negative-color image, but it is not reversed. Looking at the other side gives a reversed image. And the print is not reversed either (in this case because the negative is placed backwards in the enlarger and the lens then projects a reversed-reversed image). --Matthew Clemente 15:51, 12 January 2007 (UTC)[reply]

Invention[edit]

Alhazen (Ibn Al-Haytham), invented Pinhole camera around 1000, Around 1600, Della Porta reinvented the pinhole camera. They didnot invent at the same time.

http://inventors.about.com/library/inventors/blphotography.htm

—The preceding unsigned comment was added by Itsalif (talk • contribs).

There were no facts or sources to support the claim that it was invented by any one person, so the sentance that claimed it had been was deleted.

—The preceding unsigned comment was added by 71.177.249.74 (talk • contribs).

Worldwide Pinhole Photography Day[edit]

I think this section could use a citation. The "Worldwide Pinhole Photography Day" home page at this URL http://www.pinholeday.org/ seems like a good source to use. Anyone with more expertise on this area care to comment? --Smiller933 21:46, 6 March 2007 (UTC)[reply]

Citations always welcome. Do put one in. Tyrenius 00:53, 7 March 2007 (UTC)[reply]

New Worlds Imager[edit]

It doesn't seem to be a pinhole camera, but rather a sort of coronagraph. Haven't done the research to be certain, but it looks like the pinhole camera was an earlier design for the project. Sho Uemura 19:14, 15 May 2007 (UTC)[reply]

vandalism[edit]

should this page be protected from vandalism? it seems it's getting hit. 71.196.48.107 01:41, 23 August 2007 (UTC)[reply]

Fisheye or telephoto pinhole camera[edit]

I put this comment on Talk:Fisheye lens but thought it might be more appropriate here.

A generalized pinhole camera having different refractive indexes on either side of the pinhole can perform either a fisheye or telephoto lens function.

In this case, the radius from the center of the focal plane to any projected point is still $R=f\times \tan \theta$ as with any pinhole camera, where $f$ is the focal length and $\theta$ is the angle from the viewing axis to the point to be projected. In the general case, however, $\theta$ is a nonlinear function of the refractive indexes and the position of the point to be projected: $\theta =\arcsin {\left({\frac {n_{t}}{n_{f}}}\sin {\theta _{t}}\right)}$ , where $n_{t}$ and $n_{f}$ are the refractive indexes on the target and focal plane sides, respectively, and $\theta _{t}$ is the angle from the viewing axis to the the point to be projected, assuming the pinhole is at the origin.

If $n_{t}<n_{f}$ you have a wide-angle pinhole lens; if the difference is large enough it acts as a fisheye. If $n_{t}>n_{f}$ you have a telephoto pinhole lens. Only in the special case $n_{t}=n_{f}$ do you get a "traditional" pinhole camera with distortion-free straight lines.

Of course, the chromatic aberration in such a camera would be terrible, but it's obvious that fisheye or telephoto effects can be accomplished with a pinhole, and it's easy to simulate such a camera in a computer without the aberration effects.

Is this too obscure, or is it worth mentioning this aspect of a pinhole camera? -Amatulić (talk) 00:04, 5 February 2008 (UTC)[reply]

questions on pinhole cameras[edit]

How would the size and brightness of the image formed by a pinhole camera change if the camera were made longer. please help me out on this. thankx —Preceding unsigned comment added by 77.31.19.75 (talk) 14:14, 21 June 2008 (UTC)[reply]

Easy, same as if you got a normal projector and you point it at a wall, then you move the projector away, the image would get bigger but dimmer.

Very little gravitas indeed (talk) 18:09, 3 October 2008 (UTC)[reply]

Example image[edit]

The example pinhole camera image "A photograph taken with a pinhole camera using an exposure time of 2 seconds" is extraordinarily murky and poor quality, and not at all representative of the photographs that competent operators can produce from a pinhole camera. Please consider replacing it with a better one.

Example images, for comparison with the one here, include:

http://www.flickr.com/groups/zeroimage/pool/ http://www.flickr.com/groups/pinholers/pool/ http://www.flickr.com/groups/pinholephotography/pool/ —Preceding unsigned comment added by 91.195.142.1 (talk) 13:51, 15 August 2008 (UTC)[reply]

Pinhole Camera a camera without a lens?[edit]

Reading the article it seems weird to say that "A pinhole camera is a camera in which the lens is replaced by an extremely small hole"

A pinhole camera doesn't replace a lens with an aperture. It is a camera without a lens, cameras with lenses have apertures. Reading the article it makes it seems like a pinhole camera was a development from a camera with a lens when it is in fact the other way around, the pinhole camera being one of the first kinds of cameras.

As such if no one disagrees within the time it takes me to drink this cup of tea and smoke a cigarette I propose to edit the article so it sounds less weird.

Very little gravitas indeed (talk) 18:16, 3 October 2008 (UTC)[reply]

Light emission[edit]

Your article states that the ancient Greeks believed that light was emitted by the eyes. I can hardly imagine this. How would they have explained the lack of light without a source like the sun, torches, lamps or whatever?

I don't think they did. They believed that the eyes sent out some kind of visual rays, which were able to sense the objects of vision, but the objects did also need to be illuminated by a light source.109.150.75.67 (talk) 11:48, 30 April 2016 (UTC)[reply]

In a way this idea is much closer to sonar (by making sounds and waiting for the echo, like a bat does) than to light. —Preceding unsigned comment added by 80.141.175.42 (talk) 20:51, 4 October 2008 (UTC)[reply]

Strange calculation of pinhole size[edit]

Under "Selection of pinhole size" there are some strange calculations where in one example for focal length inch is used and in the other example cm is used. In reference 14 and 15 there are links how the calculations are done. --83.85.49.156 (talk) 02:12, 14 July 2016 (UTC)[reply]

pinhole image projection direct viewing[edit]

Pinhole camera
Camera obscura
Solar_eclipse#Viewing
Pinhole (optics)
Pinhole camera model (Redirected from Pinhole projection)
Magic lantern

Some readers come to WP seeking info about direct viewing of pinhole projected image, such as for eclipses. There are many related WP articles, perhaps most relevant Pinhole camera, but none that do a great job of discussing the subject. (Also, a good discussion might mention that with care and fiddling ordinary hand-held binoculars can do quite a good job of projecting a clear and sizable image onto a safe surface.)-71.174.177.142 (talk) 21:44, 21 August 2017 (UTC)[reply]

Linear magnification[edit]

Is the ratio of the image distance to the object distance m=v

m=hi

     h. Sarfo809 (talk) 21:28, 21 January 2019 (UTC)[reply]

Selection of pinhole size needs rework[edit]

Reference 14, Rayleigh (1891) refers to Joseph Petzval’s formula as: „2r² = fλ, where 2r is the diameter of the aperture“. Mind: 2*r² and NOT (2r)² ! If you substitute r = d/2 you get for the diameter of the aperture/pinhole: 2 * (d/2)² = d² /2 = f*λ and d = √2 * √(f*λ) or d = 1.41 * √(f*λ) Where d is the pinhole diameter, f is the distance from pinhole to image plane („focal length“) and λ is the wavelength of light. This is so in every system of measurement – metric or US/imperial – only all the parameters must have a dimension of the same system.

The optimum pinhole size can be derived from Fraunhofer’s approximation of the diffraction pattern behind an aperture. If an optimum is found where the pinhole diameter equals the diameter of its image on the image plane (the Airy disc, the central peak of the distribution of light intensity), then: d² = 2 * 1.21967… * f * λ or d = 1,5618 * √(f*λ) (The factor 1.21967… , commonly rounded to 1.22, is the value of the first zero of the intensity function and marks the border of the central peak which is called Airy disc)

Matt Young (1989), Reference 18, deducts on p. 650 correctly for the „best pinhole“ in an equivalent form to the formula above - where s is now the pinhole radius and r the radius of the image/Airy disc: r = 0.61 * λ * f / s = s and therefore s² = 0.61 * λ * f or f = (1/0.61) * s²/λ But then he writes: „… or, roughly, where f = s²/λ“ In my opinion, to ignore the factor 1/0.61 is not just „rough“ but simply wrong! Unfortunately he furtheron only uses f = s²/λ when he continues to draw his very misleading Fig.7 with his experimental data. This results in an incorrect graph for the Fraunhofer diffraction. Without knowing details of his experimental data it is impossible to know if his data points have the same 1/0.61 bias or not. In my opinion, Fig.7 is pretty worthless! Lei-Fidelity (talk) 08:39, 5 July 2021 (UTC)[reply]

No. If you look at the graph, you will see that the optimum pinhole diameter is exactly f = s²/λ, that is, where the pinhole is a Fresnel zone plate with a single zone. Petzval's estimate is wrong. Have you read Young's papers?

Theopticist (talk) 22:07, 15 July 2021 (UTC)[reply]

Or, to put it another way, the experimental measurement takes precedence over a theoretical estimate. Theopticist (talk) 00:15, 16 July 2021 (UTC)[reply]

Yes, I have read Young’s paper (The Physics Teacher, 1989). Yes, Petzval wasn’t absolutely correct. But Fraunhofer was correct and Young derives his formula correctly as s² = 0.61 * λ * f (p.650, left column). Only then he ignores the factor 0.61 to arrive at f = s²/λ, which is incorrect.

If I look at Fig.7 I do see the optimum at exactly f= s²/λ, but only because he has drawn the graph that way. The curve, representing farfield diffraction, should have its minimum at f = (1/0.61)*s²/λ = 1.64*s²/λ and not at f=1 of his units.

I do not doubt his experimental measurements, but I can’t see a way to verify them. If he has repeated his error when transferring his measurements into the graph, then they certainly fit a likewise erroneous curve. So I still believe that Fig.7 is not a good illustration with respect to the optimal pinhole diameter. Kind regards Lei-Fidelity (talk) 12:33, 16 July 2021 (UTC)[reply]

I will look at the paper later on, but I can reasonably assure you that the graph is correct: The experimental values of s²/λ are simply calculated by measuring the diameter D of the pinhole, and calculating D²/4λ. That has nothing to do with diffraction, Fraunhofer or other. That the result is correct is attested by the fact that the pinhole, as I noted above, occupies a single Fresnel zone, as we might have predicted if we had thought of it (as far as I know, no one did). Any other calculation of the optimum pinhole diameter is an estimate and apt to be off by a substantial factor.

As for Fraunhofer diffraction, remember that Fraunhofer diffraction is an approximation, and the optimum pinhole diameter is within the Fresnel or near-field region. The diffraction pattern there is not an Airy disk. Any approximation based on 1.22 λ f/D is bound to be in error. It is not *exactly* true that the optimum pinhole diameter is found where the 2 curves cross.

That said, I will get hold of the paper and try to figure out why you think the x-axis scale should be s²/0.61 λ.

Theopticist (talk) 22:14, 17 July 2021 (UTC)[reply]

I quit! I’ve now been spending hours to try to understand Young’s paper (has been raining all day;-)) and found only more questions and hardly any answers.

(1) When he introduces a normalized resolution limit (p.650, right col.) this is a transformation of the coordinate system: r -> y=r/s. Likewise, the normalized focal length implies a transformation: f -> x=fλ/s². Thus his new y-axis shows the relation of image size r and pinhole size s, which is dimensionless and not “in units of s”. The new x-axis shows the dimensionless quantity fλ/s² and not “units of s²/λ”. The line representing far-field diffraction and the one for ray optics are drawn correctly.

(2) The image size is determined by two opposing effects of ray optics and diffraction, and ALWAYS by the two of them. This can be expressed as: r = r_RAY + r_DIFFR and the formula r = s + 0.61*fλ/s. Differentiating dr/ds and setting to zero gives the minimum at s = √(0.61) * √(fλ) = 0.781 * √(fλ). This is the same as the formula in the article, where it is only expressed in terms of the pinhole diameter: d = 1.562 * √(fλ).

Well, this actual image size is the only thing that can be observed or measured in a photograph. For the optimal s, the corresponding actual image size can be found by the original formula as r =2*s. Nothing he has measured can be smaller than twice the pinhole size. In his graph the minimum of the normalized resolution limit must be “2” and NOT “0.61”.

Moreover, I believe the least thing Fresnel diffraction will do is to focus the light waves, not even: “there is a (weak) focus” at fλ/s²=1 (p.651, right col.).

Anyway, I will spend no more time on a paper which does have a lot of truth in it, but combined with so much fog, that it’s hard to see through. Nevertheless, Theopticist , thank you for your valuable comments and your time. Do use this Fig.7 as a historic attempt to reveal the mysteries of pinhole cameras – but don’t trust in it too much!

Kind regards Lei-Fidelity (talk) 10:28, 18 July 2021 (UTC)[reply]

I do not know why you are having so much trouble with that paper. I am busy right now and will note only that your (2) plainly shows that you do not understand. The image radius is *not* given precisely by r(ray) and r(diffraction). Fraunhofer diffraction pertains only in the far field, and s²/λ is not located in the far field. Things are very much more complicated in the near field than you think, and Fresnel diffraction, not Fraunhofer, pertains there. Your adding the 2 radii is a good start, but it is imprecise and should not be taken seriously. (It is an error that has been made before, but I forget where it was published, so you are in good company. I do not intend to be condescending, but think I also made the same error as an undergraduate, so I remember it well. It results in an image diameter well larger than the experimental value at s²/λ. The image diameter in the near field is simply not given by the pinhole diameter plus a contribution due to Fraunhofer diffraction, though it is initially tempting to think that. You are mistaken in claiming that the image can never be smaller than the pinhole radius.)

As for Fresnel diffraction not being able to focus, I direct you to the Wikipedia entry on the Fresnel zone plate, which focuses entirely by diffraction. As I have noted, when the image distance is s²/λ, the pinhole is a Fresnel zone plate with 1 zone, and it creates a weak focus. Indeed, the figure explicitly shows the resolution limit dropping from ~1.5s to perhaps ~0.7s before increasing as Fraunhofer diffraction takes over.

Regarding (1), I think that the graph in the Wikipedia article is substantially the same as in Young's 2 papers, and the axes are both labeled correctly: the x-axis probably should have been called "object distance," but it is indeed expressed in units of s²/λ. Likewise the y-axis is expressed in units of s. Normalized variables are very common in physics; I do not know why you have difficulty understanding them.

As a fan of and occasional contributor to Wikipedia, I want to thank you for the effort you are apparently putting in, but I am afraid that you will need to brush up on diffraction theory before you will have any hope of understanding the paper in as much detail as you seem to want. Counting the Applied Optics paper, the work has probably been reviewed by at least 4 referees, and I can reasonably assure you that it is correct.

Regards and best wishes,

Opticist

Theopticist (talk) 22:28, 19 July 2021 (UTC)[reply]

Pinpoint=Pinhole??[edit]

The description of a scheme to rapidly put very small images on a cylinder ascribed to Edison seems unlikely to have used a pinhole camera. lenses were available, and speed is described as a problem. Is the pinpoint size of the images being confused with a pinhole used to make them, and the material better placed on another page? Midgley (talk) 23:28, 26 November 2022 (UTC)[reply]