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01-09-2013, 05:29 AM   #1
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Digital sensor back for 35mm

This is not exactly related to Pentax Film SLR but hopefully it's not a wrong forum too.

Nikon patents digital sensor back for old-school 35mm film cameras

Nikon patents digital sensor back for old-school 35mm film cameras

Earlier there were a few attempts but nothing from biggies like Nikon. So do you think Nikon has some serious ideas here?

01-09-2013, 05:42 AM   #2
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See this thread:
https://www.pentaxforums.com/forums/general-photography-industry/208884-nikon-beat-us.html
01-09-2013, 07:59 AM   #3
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Oops. I missed it, thanks & sorry for the duplicate thread.
01-09-2013, 09:16 PM   #4
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I will believe it when I see it.

The main issue is sync'ing the shutter and wind mechanism with the digital back. For cameras that support an active data link between the back and the camera body, this is possible. For other, more simple models...


Steve


(...perhaps it makes a difference that Nikon still makes pro-level 35mm film cameras?)

01-10-2013, 12:21 AM   #5
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QuoteOriginally posted by stevebrot Quote
The main issue is sync'ing the shutter and wind mechanism with the digital back. For cameras that support an active data link between the back and the camera body, this is possible. For other, more simple models...
Steve
For other, more simple models, one can use the flashbulb synch.
01-11-2013, 08:44 AM   #6
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QuoteOriginally posted by asaru Quote
For other, more simple models, one can use the flashbulb synch.
This is true. I had forgotten that as a work-around. Though I am not sure that it would work The X-sync fires immediately AFTER the leading curtain completes its travel, so there would be a millisecond or more lag depending on the system. It would also be limited to x-sync speed or slower. What is unclear to me is how a flash sync system would signal the sensor on trailing curtain close? (I.e. exposure done...time to process capture...)


Steve


(there are so many reasons why this has never been done...)
01-11-2013, 06:02 PM   #7
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QuoteOriginally posted by stevebrot Quote
The X-sync fires immediately AFTER the leading curtain completes its travel, so there would be a millisecond or more lag depending on the system....

You would use the FP sync, as described here.
01-11-2013, 07:15 PM   #8
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QuoteOriginally posted by asaru Quote
You would use the FP sync, as described here.
Yes, FP would work to signal (fires just prior to leading shutter launch). Again, there would be no mechanism to tell the sensor when the shutter is closed. There is also the issue that FP sync is relatively rare. It sort of disappeared at the end of the bulb flash era.

I have a number of 35mm film cameras (about 20 at last count) and only my SV, Spotmatics, Mamiya 1000 DTL, and Pentax KX support FP sync. The others support X-sync only and in one case (Singlex TLS) X and M-sync. That last case was fortuitous back-in-the day since FP bulbs were more expensive than M bulbs and I did not have the cash for an electronic flash. You had to be careful though with M-sync. Compatible shutter speeds varied according to bulb type!

I may be wrong, but I believe that the LX and MX were the last 35mm Pentax bodies to support FP sync.

As I mentioned above, the task is not impossible, but would work best with cameras that support data backs. The exposure done signal is supplied by the write command to the databack (fires immediately at the end of exposure).


Steve


Last edited by stevebrot; 01-11-2013 at 07:32 PM.
01-11-2013, 07:33 PM   #9
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As I understand it, the FP sync closes the connection between the inner and outer receptacles of the PC socket at leading shutter launch, and reopens it at trailing shutter completion. In other words, there's no "impulse signal", but the effect is to close (and reopen) an external circuit connected through the PC socket. Which is what you'd expect. given that the FP sync belongs to wholly mechanical cameras without any internal circuitry whatever.

But in this case this is precisely what we want and need to actuate and turn off the electronic sensor. Any lead or trail times can, I suppose, be dealt with by automatically adjusting the light sensitivity (effective ASA) of the sensor.
01-11-2013, 07:49 PM   #10
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QuoteOriginally posted by asaru Quote
As I understand it, the FP sync closes the connection between the inner and outer receptacles of the PC socket at leading shutter launch, and reopens it at trailing shutter completion.
Some may work this way, but that would not be required unless the camera supported extended-burst electronic flashes. (You need to tell the flash when to stop.) In the Pentax lineup, that would be one 35mm, FP-sync model...the LX and I am not sure that feature is supported through the FP socket. In general, support for extended-burst flashes would be the exception rather than the rule and often enough was/is a dedicated and proprietary feature mediated through the hot shoe.

FP sync was originally intended for use with flash bulbs that supplied consistent light for about 1/100s and their purpose was to allow for faster flash sync (> 1/100s) with focal plane shutters. (The total dwell time of the slit was usually about 1/100s for a horizontal run shutter.) The trick was to have the bulb lit and at peak output before the first curtain opened and to sustain that output until the trailing curtain finished. There was no need to signal the flash to stop or to keep the circuit closed once the bulb filament was lit, though it may be that the contact may remain closed on some models until trailing shutter finish as an accident of design. (Remember that for FP the trigger event is fired 5 milliseconds BEFORE the shutter is released and is independent of the shutter cycle itself.)


Steve

(I will get out my continuity tester and see what the behavior is for the supporting bodies that I have.)

Last edited by stevebrot; 01-11-2013 at 07:59 PM.
01-11-2013, 08:03 PM   #11
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QuoteOriginally posted by asaru Quote
need to actuate and turn off the electronic sensor.
That is only part of the task. More importantly is the need to capture the image to memory and do initial image processing before storing it on the flash card.


Steve
01-11-2013, 08:14 PM   #12
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QuoteOriginally posted by stevebrot:
That is only part of the task. More importantly is the need to capture the image to memory and do initial image processing before storing it on the flash card.
Yes but that is just circuit design and/or (micro)coding. Nonetheless, we've passed the first real hurdle, and that is, how to drive the electronics using the existing mechanics. Even if the FP synch is just the leading-edge burst, that's enough: as long as the sensor is activated, having it shut off when there is no light in the light box is a simpler task, and in the darkness is not so time-critical. The fact that the start-event happens before light begins to enter actually works in our favor.

Some interesting electrono-mechanical-interface questions remain. For example:

(1) How to make the existing film-rewind button at the bottom double the exposure with the next shutter release, like on the old cameras?

(2) How to set ASA with the existing setting?

(3) Is there any use whatever to be made of the film rewind?

Question (1) can be solved in a pretty straiughtforward manner. Number (2) doesn't seem possible at all. Number (3) is so open, I can't wrap my head around it.
01-12-2013, 12:27 PM   #13
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QuoteOriginally posted by asaru Quote
Is there any use whatever to be made of the film rewind?
It could be used as a hand crank generator, for charging the batteries.

Last edited by Ex Finn.; 01-13-2013 at 02:59 PM.
01-13-2013, 08:41 PM   #14
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QuoteOriginally posted by stevebrot Quote
I will believe it when I see it.

The main issue is sync'ing the shutter and wind mechanism with the digital back. For cameras that support an active data link between the back and the camera body, this is possible. For other, more simple models...


Steve


(...perhaps it makes a difference that Nikon still makes pro-level 35mm film cameras?)
I wonder if the answer lies within this camera, which (I think) is not far off from a mechanical camera with a digital back.

Image from Wikipedia
01-13-2013, 11:00 PM   #15
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When you have control over the shutter release, the shutter, and the timing, you have the means to control the sensor as well. The RD-1 is based on the Cosina/Voigtlander electronic shutter, aperture-priority AE rangefinder platform. Viola! The means to integrate are readily at hand...assuming, of course, that you are building the camera and not trying to adapt by simply swapping backs.

Pity that Mr. K. (Cosina's chairman) has no desire to produce any additional digital rangefinder cameras.


Steve
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