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07-04-2008, 01:46 PM   #16
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QuoteOriginally posted by KungPOW Quote
FA Lens - Full Frame 25-35 mp (1:1 crop factor), no SR function
645D lens - full sensor use, 25-35 mp, (1.6 crop factor), full SR function

Pentax have already patented SR with FF sensors. No reason to not implement it. And what does full sensor use (FF) with 1,6 crop factor mean? Either you use the whole sensor or you don't.

07-04-2008, 09:40 PM   #17
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i think they're saying, with a FF sensor, and a 645 lens, there is a crop of 1.6 compared to the 645.
07-04-2008, 10:25 PM   #18
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69,7/43,27=1,61
07-05-2008, 01:14 AM   #19
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Who has any doubts about idea to use AF645 and FA lenses in one body,
I can offer to visit
Sinar
Sinar


Last edited by ogl; 07-05-2008 at 04:10 AM.
07-05-2008, 01:29 AM   #20
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QuoteOriginally posted by Pål Jensen Quote
Pentax have already patented SR with FF sensors. No reason to not implement it. And what does full sensor use (FF) with 1,6 crop factor mean? Either you use the whole sensor or you don't.

What I mean is that with FF and a FF lens, the image circle is not large enough for the sensor to move without losing the image off the edge. So they crop the edges, and you get a crop factor of 1.25 or so. And to use the entire sensor, SR is turned off, and there is no lost sensor surface due to sensor movement.

I would be much happier to see FF lenses used with the entire FF sensor, SR, and no cropping, but I do not know that it can be done.

What I mean by the 1.6 crop with the 645 lenses, it is the same as with a 135 format lens used on a APS-C sensor. The 135 lens gives a crop of 1.5 on the aps-c sensor, the 645 lens gives a crop of 1.6 when used on a digital FF (135 format) sensor. I understood the sensor for the 645D prototype is more or less the same size as a 135format sensor.
07-05-2008, 01:39 AM   #21
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QuoteOriginally posted by ogl Quote
Who has any doubts about idea to use AF645 and FA lenses in one body,
I can offer to visit
Sinar
YES! That I could see pentax doing. Not as many parts, but that type of modular camera.

It didn't occur to me that they might also make the sensor interchangeable. But then I did see a photo of a 645D prototype that the sensor-back hinged open. It's not a long streatch to imagine it being interchangable.

Could the camera still be weather sealed? Would it come with an allen key (hex wrench) like an Ikea bookcase?
07-05-2008, 10:12 AM   #22
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QuoteOriginally posted by KungPOW Quote
What I mean is that with FF and a FF lens, the image circle is not large enough for the sensor to move without losing the image off the edge. So they crop the edges, and you get a crop factor of 1.25 or so. And to use the entire sensor, SR is turned off, and there is no lost sensor surface due to sensor movement.

I would be much happier to see FF lenses used with the entire FF sensor, SR, and no cropping, but I do not know that it can be done.

What I mean by the 1.6 crop with the 645 lenses, it is the same as with a 135 format lens used on a APS-C sensor. The 135 lens gives a crop of 1.5 on the aps-c sensor, the 645 lens gives a crop of 1.6 when used on a digital FF (135 format) sensor. I understood the sensor for the 645D prototype is more or less the same size as a 135format sensor.
of course it can be done, it only needs a few centimeters total, to reduce shake, which translates to a mere centimeter or so of travel, per side. sony is releasing a FF camera with their SSS in it, this year
07-05-2008, 11:46 AM   #23
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Major factors in my mind

2 key factors to consider in all these speculations is 1)Lens to flange distance 2)Mirror size.
Both are of course related to each other. 2) is obsolete IF Pentax goes with a total EVF (electronic viewfinder) which I consider unlikely.
Next major thing to consider is it is anti-pentax to make things bigger than they should.
Sooo this leave only a few full frame possibilities from these "assumptions"
1) FF sensor in a typical SLR sized body. Adapters for 645 lenses as usual.
2)FF sensor in a 645 size body (unlikely due to above considerations). Only 645 lenses need apply
3)FF sensor in a modular back 645 body w/ full frame and mf sensors available.
4) MF only in a smaller body (645 lenses need adapter, ff/aps lenses still don't fit)
The aps-c and full frame lenses have the same lens to flange distance. VERY unlikely.
645 ect. are much longer so they fit on a dslr w/ adapter.
Unless Hoya changed their mind, a ff is directly fighting w/ C/N/S, which from their prev statements they ar trying to avoid.
My bet still rides on a 645 w/ modular back. Full frame sensor standard equip. (I'm a terrible gambler)

07-05-2008, 11:53 AM   #24
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QuoteOriginally posted by KungPOW Quote
What I mean is that with FF and a FF lens, the image circle is not large enough for the sensor to move without losing the image off the edge. .

No. The image circle is large enough anbd a solution is already patented by Pentax and shown by Sony.
07-05-2008, 11:55 AM   #25
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QuoteOriginally posted by OniFactor Quote
i think they're saying, with a FF sensor, and a 645 lens, there is a crop of 1.6 compared to the 645.


But it is pointless using a 645 lens on a 35mm FF sensor if 35mm system lenses are available. And they are. They are called K-mount.
07-05-2008, 11:58 AM   #26
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QuoteOriginally posted by Pål Jensen Quote
But it is pointless using a 645 lens on a 35mm FF sensor if 35mm system lenses are available. And they are. They are called K-mount.
so then why does pentax make an adapter to use 645 lenses, on k bodies? ;-)
07-05-2008, 12:19 PM   #27
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QuoteOriginally posted by OniFactor Quote
so then why does pentax make an adapter to use 645 lenses, on k bodies? ;-)


That is something you do if happen to own the 645 lenses in the first place. So far Pentax haven't been stupid enough to make an 35mm film camera with 645 lens mount. It doesn't make sense!
However, what makes sense is to make a 645 digital camera (with matching sensor 2xFF) that will take K-mount as well, but then with cropped image circle (FF). If such a beast was possible, something I doubt, it would grossly increase the market for Pentax MF digital; but it would be a very expensive FF camera.

Last edited by Pål Jensen; 07-05-2008 at 12:31 PM.
07-05-2008, 01:52 PM   #28
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Assuming the image circle of the lens is at least 53mm, and the sensor only needs to shift 5mm (diagonal) then SR on a FF sensor would be no problem.

An image circle less then 43mm, or a shift of more then 5mm would require the image to be cropped.

With my "google-fu" I was not able to find image circle values for pentax lenses. I did not try to find sensor shift dimensions.

I also cannot find the sensor dimensions for the 645D. I thought it was to be only 36mm x 24mm. Does anyone know?
07-05-2008, 02:07 PM   #29
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5mm travel is HUGE, Kungpow. here's an article that explains most of the math of how to figure out how much travel you need

Super Steady Shot with Full Frame Sensors
07-05-2008, 04:44 PM   #30
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QuoteOriginally posted by OniFactor Quote
5mm travel is HUGE, Kungpow. here's an article that explains most of the math of how to figure out how much travel you need

Super Steady Shot with Full Frame Sensors
Thanks for the link. I added a comment over there.

This info is both pessimistic and optimistic, though.
Pessimistic, because 0.5mm travel is already enough to gain 4 stops -- for any focal length. I did the math myself.
Optimistic, because much more travel is required since you can't keep the sensor centered BEFORE the shutter is actually pressed. How much isn't known from sources I know. And ignored by the source you mentioned.
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