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Digital backs on MF Is there a point, at all, to putting a digital back on a MF camera? Jerry
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John A. Lind |
There are certain specific applications for which the buisness case could be made. One that comes to mind *could* be a major catalog or advertising studio for which the work has been traditionally done using a 4x5 technical camera and reversal sheet film. There are backs made, but they're horridly expensive . . . last I looked (less than a year ago) they were in the $15k - $20k (yes, thousands) price range. That was for the back alone. No body, lens, or anything else included. The two I looked at required something along the lines of a firewire directly hooked to a computer for download of each image as it was made. For the application I've mentioned, the user would have to be doing major production work for higher end customers for such a device to pay for itself in two to three years. As to using one for something other than large studio production work that can command a very high price per photograph rendered, I don't see how it could be justified. For the price of the back alone one could buy a medium or large format system with multiple film backs and several lenses! -- John Lind
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Thanks John. I think my question was more getting at the application of a MF digital back. Is it better than a DSLR? Is it also a larger image size than a DSLR? I could see a huge advantage if this was the case, and you need to go B-I-G! Yes, a digital back for my 6x7 MF film camera is horrendously expensive (I think it was around $15 to $20k). And, let's pretend for a minute that you had all the money, and that wasn't really a concern, even if it was a stupid business decision - forgetting about payback or ROI, and all that stuff. Is it better, and if so, what are the advantages? I am aware of some of the disadvantages, all of which you mentioned, as well as un-portability (if that's a word). But, I have not heard much on the side of advantages. Maybe there aren't any. I don't know. Just wondering. Thanks,
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John A. Lind |
Jerry, Yes, it's bigger, much bigger, and the digital files these backs create are absolutely enormous. It's the reason they're tied by umbilical to a computer . . . which makes field operation very impractical. As to advantage over using film, I really don't see much other than providing work that shortcuts some of the pre-press preparation (optically performing color separation scanning for RGB or CMYK publication printing presses). Equivalent film format still has substantially greater resolution as do optical prints from film. IMVHO film versus digital depends on the entire work flow and what the output will be. One exception would be very low light and very long exposure work with which film unquestionably still rules. CCD's and CMOS sensors choke under those conditions (I've done night work that requires exposures measured in minutes; impossible with digital). -- John Lind
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Derek Holyhead |
Hi Jerry, Hi John, I think you should both rush out and get a copy of Digital Photo Pro magazine (May/June 2004 issue). For Jerry: A good article on page 86 "Is a Medium Format Back right for you?" and for John: An article on page 79 "Photo Finish, Robert Beck is a Sports Illustrated photographer..." and I quote from that article (page 80) "A lot of the photography that appears in Sports Illustrated is made under low-light conditions where film isn't an ideal medium. Digital looked like a promising solution due to its superior low-light performance and broader latitude" So there you have it from a Pro using digital for low-light and shooting for one of the world's foremost Sports mags! But don't take my word for it, buy a copy and read it for yourself. There is also an article by Rob Sheppard called "Myth:Inkjet prints fade too quickly to be used for fine-art printing" Very interesting reading. Regards, Del
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John A. Lind |
Del, I'm working routinely with luminance levels on the order of 1/8 to 1/2 foot-Lamberts. In units of EV, this is a Brightness Value in the -6.33 to -1 range. By comparison, indoor and outdoor night sporting events have a luminance on the order of 4 to 8 foot-Lamberts. In units of EV, this is Brightness Value in the +2 to +3 range. Expand the range by an EV unit on each end, especially the lower end if you wish, as stadia are neither uniformly illuminated, and luminance can vary greatly from one to another. Professional and major university sports arenas and stadia typically have noticeably more luminance than high school or junior college. I estimate that ISO 400 would work under these conditions with fast telephotos in the f/2 to f/2.8 range although I'd want to use a monopod. Brightness Value is the luminance; Speed Value, film speed converted to EV units, must be added to that to arrive at EV: Even an EOS-1D cannot handle the luminance levels I'm working with hand held with a modest telephoto in the 85-135mm range. Using 1/30th to 1/60th second shutter speed which is risky in itself, and an apertures of f/2 to f/2.8, film speeds must be in the ISO 1600 to 3200 range to handle a Brightness Value in the vicinity of -1. That's at the upper end of the range too. -- John Lind
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
Depends on what you had to shoot. iso 1600-3200 with 1/60-1/30 is what you'd get with a one regular street light. You can do timed exposures with digital. It's another thing that's recommended to use RAW for best results. Although somebody on here said that there's a diode or some electronic part that for super long exposures, the heat from it can do something to part of the picture. Noise I think was the problem.
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- Gregory LaGrange Contact Gregory LaGrange Gregory LaGrange's Gallery |
but don't know if that's true for all cameras.
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John A. Lind |
Gregory, Yes . . . it's about the level of urban night street shooting. It's also the level of church interiors . . . I can usually shoot 1/60th @ f/2.8 with ISO 1600, but there have been times I've had to load up the TMax P3200 and shoot it at EI 3200 although I'd rather be using Fuji Press 1600 or TMax P3200 @ EI 1600. Also the approximate conditions for bands in small relatively dark clubs. Again, that's at the high end of my low light work. I also do landscapes at night with zero manmade lighting (if at all possible) . . . with exposure set for what is provided by moon and starlight. That's another 5-6 stops down in light level compared to what I've just discussed. Because it can be tripoded, slower film with significantly higher resolving power can be used (compared to the high speed stuff) and lens apertures set to the "sweet spot" in the middle range. Exposure times under these conditions are on the order of several minutes. Film doesn't have the "noise" issue and artistically the results can be slightly surreal. As I understand the technologies, there are two basic types, the CCD and the CMOS sensors. The CCD was supposedly developed by Bell Labs (???) and requires a different fab (or foundry) to make them compared to nearly all other IC's. The CCD fabs are older and don't have the yield rates of current IC fabs. Consequently they're more expensive. In addition, there's nothing built into them . . . in the industry it's called "up integrating" multiple functions into a single IC. CCD cameras require more IC's also adding to cost. It also means they'll be slower if for no other reason than the paths to other IC's containing the additional functionality required for the camera to operate are significantly longer (electronic signals travel at the speed of light). Might seem trivial, but it's not given the enormous number of processing transactions that must occur when recording a digital image from the sensor. They have the inherent capability to be more sensitive to light (compared to CMOS) but whether or not a specific CCD does greatly depends on its specific design. Even so they're still subject to "noise." There are some other issues but I don't recall exactly what they are. The CMOS sensor can be made in the same fab as other, current technology IC's and are significantly less expensive, and image recording can be done faster. This is the sensor found in nearly all digital still cameras being made. Because of the up-integration, the photo-diode does not occupy the entire pixel cell in the sensor; there's other stuff located with it on the IC wafer. This reduces its light gathering capability making it less sensitive to light compared to a CCD. Some of the newer ones have micro-lenses over the tops of the photo-diodes to help gather in some of the light that would otherwise not land on the photo-diodes, but it isn't "perfect" and there's still loss (light falling on nothing to record it). In low enough light it suffers from "noise" . . . how low depends on specific CMOS sensor design. I've seen the effects of noise in digital photographs . . . usually darker and shadow areas of night scenes and other low light situations. It isn't pretty and it's nearly impossible to fix. -- John Lind
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