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Ok I've tried to work this one out and failed and tried a few experiments and failed with them as well (though I'll admit my setup was very crude and might have hindered getting the proper result).
The basic approach is something I found a guy working on where he has a stactic camera, static focal point and a stactic thin beam of light. The subject is then move through the beam of light very slowly whilst the camera take a shot in bulb mode - the result being a shot with increased depth of field after the subject has moved through the light beam.
However I've tried to recreate this (using a flash rather than constant light source, but the single strip of light remains the same) and got what I expected - a messy mess of a shot (ok so I might have to work on the exposure part a little more). But even just considering the concept I can't see how it works as to my mind the subject should end up with blurr as the focal point remains the same whilst the subject moves through it.
So does anyone here have a better understanding that might explain why this works and how?
For additional refrence the original source I found this method on: Source
Not quite sure what you/he is trying to achieve with this somewhat complicated setup? Good DOF?
Using a tripod and the "flower" or whatever held still somehow, just stop the aperture right down - f32, and then do a time exposure. With careful lighting you'd get exactly the same result (wouldn't you?), good depth of field. In fact some of his sample shots didn't have particularly good DOF (if hat's the object of the exercise) so seems a bit of a waste of time.
It works because the subject is moved through the point of focus, the beam only illuminating the part of the subject that is in the beam/in focus. I suppose it offers precision control over the field.
I can't get my head around why moving the subject during a long exposure, even with a controlled strip of light, would not just result in a blur.
If the subject remained static and the tight strip of light moved I could understand that as it would allow a much longer exposure and therefore smaller aperture.
Anybody got any clues?
Ian
Is this just a focussed stacked approach, but moving the subject and not the focus point between each exposure.
In fact i think it can't be a single exposure.
i think this might give more detail - Stackshot and shows its not one exposure.
... but if you move the subject how do you then stack the photos? Do you have to use panorama stitching software? How does it deal with perspective (or the resultant lack of it)?
Focus stacking software deals with anomolies and distortion but that's with a subject that is static through which a series of focus points move. Not sure, though I've not tried, that it could deal with a subject where the focus point remains but the subject moves. If so, the photographer in question would be better off getting a rail. Cheaper, simpler and less of a solution looking for a problem.
If it is a focus stacking technique then it would work better than having the camera on a rail because you wouldn't have to keep adjusting the light source.
Anyway, I would like to know how this guy does it?
We use this technique a lot in photomicrography when dealing with microscopic DOF width produced by optical elements. When we run out of stage range we use scanning techniques.
The same holds for light, or TEM scopes and photon detectors. - and obviously the SEM process itself.
Far better detail can be achieved with narrow-width light stacks than traditional optical stages. - but only when the subject itself is at least partially transparent.
For instance my pictures of Human Ovarian Corpus Luteum are a multi-stack image; in regards to stage movement.
- This leaves me confused to this "bulb" exposure method - I have to assume that his light source and subject are moving as this is an entirely reflected light set-up. - and won't follow the same rules as a sample that is transparent.
Quote: Anyway, I would like to know how this guy does it?
With extension tubes, reversed lenses and a decent light source.
Just to clarify a point that I think has got overlooked by some - the user is using a stackshot to move the subject automatically, but the camera is still taking only a single exposure in bulb mode. Ie this is not focus stacking through software but a totally single exposure in the camera.
Cheddar-caveman - the problem with using such a small aperture as f32 for the depth in a single shot is that diffraction will greatly soften resulting exposure no matter how well you take the shot. Generally speaking f13 is my lowest limit with aperture on a 1.6 crop camera body and f16 is most peoples with a fullframe camera body. Thereafter that point the sharpness continues to drop quite noticeably - for websized shots you can go lower before the webresize (with sharpening of course) suffers, but the larger fullsize shot will still be suffering.
Cambirder - my thinking is that flash should work if you can narrow the light to a single thin beam - at that point a flash burst of light is no different to a slower exposure time whilst using a constant light source. Sadly in my crude tests I've not managed to get the single light beam thin enough nor under good control.
Swwils - in this method only the subject itself is moving through the static beam of light (as opposed to his previous method moving camera and light at the same rate toward the static subject).
When it comes to focus stacking software you can move the camera closer whilst taking a series of shots or you can move the subject closer to the camera - it really wouldn't matter either way so long as aside from the distance changing between the two all other parts of the subject remain still and you manage to get a full series of overlapping (depth of field) shots to stack.
You can also just adjust the focus of the camera and move the focus plane through the subject - though I've always considered this approach more limited as you can only go so far before I would expect the magnifiaction change of moving the focus plane comes into effect.
I'm glad I'm not the only one confused by how this method works, I did recall that I spoke to the photographer in question and he said this:
"You would think that things could merge but it doesn't happen as far as I can tell. Light on a part of the object behind that has part of the object closer to the lens is hidden from the sensor by that part so that the part already recorded on the sensor remains intact - if that makes sense."
though it still leaves me confused as to how it works. Be interesting if anyone can recreate the effect - might be then that we start to understand the process a little better.
Quote: Anyway, I would like to know how this guy does it?
....and a fridge
Pfft fridges are cheating
Just gotta get up early in the morning or head out after a quick rainstorm to find all the sluggishly cold bugs you could need without having to freeze their little legs off
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