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How can one capture shots like this where a long, small tube like a gun bore is evenly illuminated along its length?

In this sample the harsh reflections off the breach suggest it was illuminated from the front, but I can't imagine any means of evenly pumping light into a tube no more than .45" in diameter (and as small as .22") while at the same time having the lens centered on the bore's axis, which is necessary to get its full length.

Update: In response to answers so far I did some experiments with single exposures on a comparable barrel. I pasted details as a separate answer below.

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7 Answers 7

I can see two possible ways this shot was done:

  1. Light was injected where the cartridge would go. We can't really see what is back there in the picture. Some LEDs could have been carefully placed inside or almost inside the gun, and the wires run so that they would be obscured in the picture.

  2. A beam splitting mirror was used. The camera was looking thru a beam splitting mirror. A light source was then bounced off the mirror face away from the camera. This allows the light to be shined in-line with the view axis of the picture. You have to make sure that what the camera sees reflecting off the mirror doesn't show up in the picture. Note that the light source will illuminate whatever object you put there too. This is why you put something flat black there. A large dark open area also works since the light will have diminishing effect on distant objects.

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Ah ha: I hadn't considered #2! That sounds likely. I can't imagine how #1 would work since the breech appears to be locked, and even if it had a small gap wouldn't the light reflections fall off severely as they move down the barrel towards the camera? –  feetwet Aug 2 at 14:46
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@feet: The inside of the barrel is viewed at such a glancing angle that it largely works like a mirror. I don't think you are seeing it illuminated as much as you are seeing reflections of the back of the breach. –  Olin Lathrop Aug 2 at 14:48
    
Looks like beam splitters are frequently used by serious macro photographers. I just came across this fascinating thread: photomacrography.net/forum/viewtopic.php?t=24448 –  feetwet Sep 18 at 17:45

The photographer shows and discusses his lighting set up here: https://www.flickr.com/photos/29689383@N02/5615386358/in/photolist-9ydjJb

Also, he mentioned elsewhere that he uses focus stacking.

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Good to know he was probably using focus stacking. The lighting setup he shows here wouldn't work the same for the picture in question because here he's able to place a flashlight directly into the chamber. In the original question, because the slide is locked forward, the only access to the chamber is from the front or through the magazine well, though it occurs to me that the mag well could be polished enough that it would bounce the light up as we saw. BTW, can anyone identify the lens he's using in this setup picture? –  feetwet Aug 3 at 18:05
    
FYI, looks like he's using a simple Nikkor 35mm AF-S DX lens. –  feetwet Sep 23 at 15:21

When reverse engineering a lighting setup always apply the principal of Occam's Razor:

among competing hypotheses, the one with the fewest assumptions should be selected

http://en.wikipedia.org/wiki/Occam%27s_razor

Before introducing exotic lenses or beam splitting mirrors, let's examine the requirement for the incoming light to be perfectly aligned to the lens axis.

The bore is made of metal, and metal reflects light very well. If you shine a bright light into the barrel from any direction then it will bounce around inside illuminating the length of the barrel, removing the on axis restriction.

I don't know enough about firearms to say whether light could be introduced from the rear (presumably the same way the bullet enters the barrel), but again applying Occam's Razor, the simplest way is through the front!

The solution that seems simplest to me would be a multiple exposure with one bright light angled to illuminate inside the barrel, and a second designed to light up the front of the pistol. It's possible even that this was a single exposure, place a black plastic sheet touching the muzzle with small hole where the barrel is, hit it with a powerful strobe from and angle and whilst keeping the shutter open remove the sheet and let the ambient light burn in over several seconds. But a multiple exposure is simpler.

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This is just a guess and may not be the way these photos were created, but one way to produce such a shot would be with a mirror lens. A mirror lens is a catadioptric system similar to a Schmidt-Cassegrain or Maksutov telescope. All of these systems have a fairly large secondary mirror placed in the center of the main objective lens and all of the light entering the lens does so through a donut shaped opening around the secondary mirror in the center. A small light or flash placed in front of the secondary mirror on the center of the lens' optical axis could illuminate the barrel and the other parts fof the gun in the breech behind the barrel.

Here is one such lens mounted on a Sony Alpha 55:

enter image description here

For more about mirror lenses, please see What kind of mirror in a mirror lens?

Additionally, to get that kind of Depth of Field some form of focus stacking was likely used.

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Interesting idea! But could that possibly work for a macro picture like this? All mirror lenses I've seen are very telescopic. If there is such a thing as a macro mirror lens I can't imagine how it would be able to focus down a tube with a diameter smaller than its center mirror. –  feetwet Aug 2 at 14:49
    
With the high resolution of today's DSLRs one could crop significantly to get there instead of using a true 1:1 macro lens. I couldn't find a way to look at the EXIF info to see the resolution at the link on Flickr. –  Michael Clark Aug 2 at 15:56
    
Since the interior diameter of a .45ACP bore is about 11.4mm, with a true 1:1 macro the inside of the barrel would be roughly half as wide (short side in portrait mode) as the frame using a 36x24mm FF sensor. With a 24x16mm (give or take) APS-C sensor the barrel would be over two-thirds the width of the short side. –  Michael Clark Aug 2 at 16:01
    
WRT the center mirror: Remember, rays from all point sources of light in the field of view strike every point on the surface of the front lens. That de-focused light is then focused at the film/sensor plane. There is no "blind spot" in the middle of a lens or telescope with a secondary mirror in the optical path but rather an overall reduction of brightness for the entire scene, not just the middle of the scene. –  Michael Clark Aug 2 at 16:07
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@feetwet from a bit on an older 500mm f/8 Reflex Nikkor lens - " Overall, the lens is much more compact in size than earlier version of the Reflex-Nikkor but a significant improvement was its close focusing ability which has improved down to just 1.5m (4.9ft.) from the 4m (13ft) range found on earlier version. Another amazing feat was its reproduction ratio which stands at 1:2.5 at its closest focusing distance." - that isn't too far away and a rather nice reproduction ratio. –  MichaelT Aug 2 at 17:56

Another possibility is that it could be actually two exposures edited into one. For the hole, a long exposure could be used that captures the ambient light and from the tip outside is a regular exposure.

It could also be a very long lens with two or more light sources on opposite sides of it to avoid shadows, again with two exposures, because the rest of the gun does not seem to be illuminated by them.

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The trick in any case is to get even illumination down the bore. Ambient light doesn't do that (I've tried). And based on the reflection from the breech it appears he has managed to get a light shining straight down the bore. I have considered the possibility of a very long lens that allows something like a ring light to be close enough to the bore axis. I'll try it, but I'm skeptical it will work. –  feetwet Aug 3 at 15:02
up vote 1 down vote accepted

I did some experiments on a 9mm pistol barrel, which is 20% narrower than the .45 used in the reference photo. The barrel I used was potentially 1 inch longer than his (I used a 5.3"; he may have used a standard 5" 1911 or a 4.25" Commander-length).

I used a 300mm lens placed at the minimal focal distance (5 feet) and ran it with minimal aperture (f32-f40). Even with that aperture the focal plane is not quite deep enough to get the barrel in focus from breech to muzzle, suggesting that focus stacking is necessary.

Anyway, using ambient light a single 30s exposure produces this: 30s exposure at ISO 200, f/32, 300mm, ambient light

Using two flashlights held as close to the lens barrel as possible produces this 1s exposure: 1s exposure at ISO 200, f/40, 300mm, dual illumination

Update: I went back to this with a new 90mm macro, illuminated through the chamber from above with the slide open, and stacked three shots taken at f/22 in Photoshop. I'm satisfied that with a lot of careful tuning one could produce something like what was proposed. Here's the result:

3 images focus stacked in Photoshop

Another Update: I got a 35% reflective beam splitter and tested the following setup with a 60mm macro lens:

enter image description here

This does indeed seem to be a viable solution to coaxial illumination, producing the following image at f/20:

enter image description here

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Rather than focusing on the front of the barrel (so that half of your DoF is wasted in front of the subject) did you try focusing halfway between the barrel and the breech? –  Michael Clark Aug 3 at 19:36
    
I tried to focus halfway. Obviously I ended up front-biased. I have a really hard time visually nailing a focal point with the Sony A300 I'm using. Is there some trick I don't know? –  feetwet Aug 3 at 20:25
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I think the photo you're trying to imitate is a composite, for the simple reason that the face of the closed bolt in a M1911 sits a bit further away from the muzzle than the trigger guard. There is no way the muzzle, the face of the bolt, and the entire bore could be in sharp focus, while the front of the trigger guard is not.

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Yes, there seems to be a consensus that the reference image was produced via focus stacking. –  feetwet Sep 16 at 14:36
    
It could be more than just that. What about the difficulty of lighting the bore that way? I don't see any reason to assume the gun was assembled when the photos were taken. –  Kevin Krumwiede Sep 16 at 17:09
    
Ah, I see what you mean about compositing. Well, he does say flickr.com/photos/zorin-denu/7700482780/in/photostream that the gun was fully assembled and slide forward for the photo. Given the light color and reflection I'm guessing he has a snoot on an LED light resting on his camera at about 2 o'clock. I'm also going to assume he was using the same lens as in this photo: flickr.com/photos/29689383@N02/5615386358/in/photolist-9ydjJb Can anyone identify that lens? –  feetwet Sep 16 at 21:19

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