macro photography: generating a plane of light?

[dh003i]

The thought of how much computing power would be needed to process image stacks from 4x5 (or even MF) digital back is mind-boggling. In short, you'd need nothing short of a $20,000 supercomputer!

Some of the medium-format backs are 50 megapixels. The Betterlight scanning have a 3x4in scanning area and range from 19 - 139 megapixels (for the 19MP one, those have to be the cleanest sharpest megapixels you'll ever see!). I don't know about your computer, but my computer is going to crash just thinking about doing an image stack of hundreds (or even thousands) of 19-139 megapixel images. Not to mention the size requirement: 50-400 MB per file times say 100 - 2000 stacks! That ranges from a DVD's worth of information (~5GB) to a hard-drive's worth of information (~271GB!).

I have a Q9550 Intel quad-core CPU, 8 GB RAM, and a 1TB 7,200rpm HD. Working with 4x5 files in GIMP alone sometimes can cause it to hit the virtual RAM (I forget what it is called...for he most part, with 8GB of RAM, you never hit the hard drive...except when doing significant transformations to 4x5 images).

I think that to work with many stacks of even higher end medium format digital images, you'd need a dual 12-core AMD operon machine with 256GB of RAM and a motherboard that could support that much. Price so far? ~$12,900.

These files are big, and normal hard drives are very slow (~133 MB/s)...so if you want to work with them in a reasonable manner, you'll need a very fast hard drive. The best consumer grade one at the moment is a ~$1700 400GB 270 MB/s hard drive. But that might not be fast enough! You might need something more like a 800 MB/s or even 1.5 GB/s read hard-drive: $7,500-$10,000.

Oh, and you can tack on an $200 SSD if you can't hook link your digital setup directly to your supercomputer.

[Struan Gray]

I don't know how the commercial and freeware stacking programs do their stuff, but the only reason to have the whole stack in memory at once is speed (and convenience of programming). I have squeezed a stacking program into a total memory space much less than a single frame. An efficient version might need a few times the single frame size.

One caveat with stacking is that with a wide aperture lens you can actually see behind objects. Stacking algorithms which just pick the sharpest parts of the stack can be fooled into inverting the shape of textured objects. More sophisticated routines can extract a full 3D model of the thing being imaged, and make better decisions about what should be visible from the nominal viewpoint.

[Dr Klaus Schmitt]

I would recommend Zerene Stacker, the best currently staking software of all I have ever tested and used over the years (I am not related in any way, just a satisfied customer). http://zerenesystems.com/stacker/ It is free for 30 days and if convinced only a moderate cost applies.

[Dr Klaus Schmitt]

Rick Littlefield, the developper and macro specialist is active here http://www.photomacrography.net/forum/viewforum.php?f=8 and is always available to answering technical issues.

[Dan Fromm]

Nathan,

I'm having a Micro-Nikkor 55/2.8 and Tokina AT-X 90/2.5 rigged by S.K. Grimes to reverse mount to a 4x5 board, with a Polaroid MP-4 shutter mounted on the subject side. <large snip>

You should have ordered a stepped bushing threaded male M52x0.75 (usual Nikon filter thread) at the front and male M40x0.75 (front of #1 shutter) at the rear. Screw bushing into lens, screw bushing+lens into shutter.

Putting lens on board, shutter on lens' bayonet is more expensive and costs working distance. Not the smart way.

[dh003i]

You should have ordered a stepped bushing threaded male M52x0.75 (usual Nikon filter thread) at the front and male M40x0.75 (front of #1 shutter) at the rear. Screw bushing into lens, screw bushing+lens into shutter.

Putting lens on board, shutter on lens' bayonet is more expensive and costs working distance. Not the smart way.

I talked with Adam at SK Grimes about this, he thinks "front-mounting" the MP-4 shutter on the rear of the lens, which would be reverse mounted, is the cheaper way to go. I think the way you're suggesting would be more expensive, because then I'd need to buy a #1 shutter. And a #1 shutter has about the same sized hole as the MP-4. I tested this out (by hand), and reverse mounting it to a shutter of that size at the lensboard plane cuts off a significant part of the image circle.

Screwing the front of the lens into a #1 shutter and then mounting that would seem to cut off the image circle because the front of the lens is slightly larger than the rear of the lens. Also, because the front is recessed, the shutter would have to be further away from the lens, cutting off more image circle. The same thing would happen with my Tokina 90/2.5 front mounted into a shutter: a lot of the image circle would be cut off. I think this would prevent the lenses from being used at their otherwise smallest magnification they could be used at on LF (~2.6 - 2.8x, depending on if you assume the entire 4x5 is used or only 3.75x4.75": sqrt(3.75^2 + 4.75^2)*25.4/43 - 1 = ~2.6x. sqrt(4^2 + 5^2)*25.4/43 - 1 = ~2.8x.

I think I'd need a #3 shutter to do what you're suggesting and still be able to work at the lower magnifications possible with

[Dan Fromm]

What do you think the MP-4 shutter is? It is a #1 Copal Press shutter with no diaphragm.

How do you think I use my macro lenses? They all go in front of a #1. I started with an MP-4 shutter 'cos they're inexpensive, switched to a cock-and-shoot #1 after I found one that I could afford 'cos when shooting a low magnification out-of-doors 1/400th makes it easier to overpower ambient with flash without stopping down too much.

BTW, I don't know who ran the lathe, but SKGrimes made my reversed Nikkor (with 52 mm filter thread)-to-#1 shutter adapter.

Think hard about the geometry of vignetting. Use a similar triangles model. You'll be astonished by what can be done with a #1.

A reversed Nikkor's minimum flange-to-subject distance is 46.5 mm, of which a #1 will eat 20 mm. And then there's the adapter ...

[Nathan Potter]

As Struan suggests for image stacking, all you need in each layer is that portion of the image that is in reasonable focus, which would be a tiny fraction (1/2000 for example) of the total pixel count (and memory) comprising the final image. This would require some pattern recognition on the part of the software so would need to be evaluated based on your objectives. dh003i, of course 4X5 capture is not available as you point out so your enlargement resolution requirements could not be met, I think, even with medium format capture.

Nate Potter, Austin TX.

[dh003i]

As Struan suggests for image stacking, all you need in each layer is that portion of the image that is in reasonable focus, which would be a tiny fraction (1/2000 for example) of the total pixel count (and memory) comprising the final image. This would require some pattern recognition on the part of the software so would need to be evaluated based on your objectives. dh003i, of course 4X5 capture is not available as you point out so your enlargement resolution requirements could not be met, I think, even with medium format capture.

Nate Potter, Austin TX.

Apparently, I was just made a liar out of. Canon has just developed a 8 x 8 inch CMOS sensor (no word on the resolution yet, but I doubt they're using photosites 10 times the size of other sensors)..