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02-21-2015, 01:32 PM   #16
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QuoteOriginally posted by mee Quote
So your baseline is a cell phone camera? That is a very strange comparison.

Cell phone camera sensors are tiny.. TINY. As a result, the performance is affected negatively compared to an SLR. But the main issue, already shown in the graphic, is the OVF mirrorbox and register distance that HAS to be there for K mount.

The cell phone is without a mirrorbox. If your cellphone had a mirrorbox and K mount ring it would be the size of a Pentax K mount camera.

Besides, you're attaching a long tube (camera lens) to the end of it. Can you imagine attaching a 60-250 f/4 or other large sized lens (even the DAL 18-55 for that matter) to something as thin as your cellphone? The handling would be all wrong. You want a thick base to grip with all of that weight on the front of your camera. It makes little sense to shrink the body size as long as the lens size (and weight) remains large.


No not the camera. I mean just all the internal electronics in general. The LCD the computer chips. Basically saying the circuit board in the DSLR could probably be made to be super thin along with everything else.

---------- Post added 02-21-15 at 12:35 PM ----------

QuoteOriginally posted by mee Quote
So your baseline is a cell phone camera? That is a very strange comparison.

Cell phone camera sensors are tiny.. TINY. As a result, the performance is affected negatively compared to an SLR. But the main issue, already shown in the graphic, is the OVF mirrorbox and register distance that HAS to be there for K mount.

The cell phone is without a mirrorbox. If your cellphone had a mirrorbox and K mount ring it would be the size of a Pentax K mount camera.

Besides, you're attaching a long tube (camera lens) to the end of it. Can you imagine attaching a 60-250 f/4 or other large sized lens (even the DAL 18-55 for that matter) to something as thin as your cellphone? The handling would be all wrong. You want a thick base to grip with all of that weight on the front of your camera. It makes little sense to shrink the body size as long as the lens size (and weight) remains large.




You've completely missed my point.. what I'm saying isn't in regards to the thickness of the mirror box. I'm talking comparison of film SLR vs DSLR.

02-21-2015, 04:37 PM   #17
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Between film SLRs and DSLRs from Pentax there is no much difference.

MZ-S : x 64.0 mm (D)

K-7 : 72.5 mm (D)

K-S1 : x 69.5 mm (D)
02-21-2015, 05:39 PM - 1 Like   #18
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I have been asking this question for a long time and no one has ever provided a legitimate engineering or design answer. You can see in that great cut away above there is a huge gap between the back of the sensor and the nearest circuit board. Why does that gap need to exist or be so large?

The mirror box clearly consumes a majority of the mount to sensor/film plane distance. But my old film bodies had the film plane much further to the back so the overall depth of the camera body was less than any DSLR I've used.

Here are a couple interesting items from the manuals of the Nikon F100 and Pentax K-5II showing the difference in the location of the film/sensor plane.
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02-21-2015, 06:02 PM   #19
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QuoteOriginally posted by shaolen Quote
Basically saying the circuit board in the DSLR could probably be made to be super thin along with everything else.
The K-01 already went one better, and got rid of the circuit board entirely by replacing it with a point-and-shoot-sized board over on the grip side. That still left the sensor, SR chassis and LCD (about 13mm total). They might have shaved a couple mm off the LCD with an air-gap-less panel, but that still would have left 11mm behind the focal plane, compared to 3.5mm on a K1000.

QuoteOriginally posted by JeffB Quote
Why does that gap need to exist or be so large?
As others have said, it's probably to dissipate heat from the sensor (and circuit board). With multiple layers of glass on the front side of the sensor, the back is the only place the heat can go.


Last edited by THoog; 02-21-2015 at 10:03 PM. Reason: 49-45.46=3.5, more or less
02-21-2015, 06:16 PM   #20
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Air is a very poor conductor of heat. A solid copper heat sink mounted directly to the sensor would be much more efficient. But that probably would not work too well with the "SR" movement of the sensor.
02-21-2015, 06:21 PM   #21
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QuoteOriginally posted by JeffB Quote
Air is a very poor conductor of heat. A solid copper heat sink mounted directly to the sensor would be much more efficient. But that probably would not work too well with the "SR" movement of the sensor.
But it's a great ventilator..
02-21-2015, 06:26 PM   #22
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QuoteOriginally posted by Steve.Ledger Quote
But it's a great ventilator..
Yep, convection, not conduction, is dissipating the heat.
02-21-2015, 06:28 PM   #23
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Mine seem smarter than me most days ; )

02-21-2015, 06:41 PM   #24
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QuoteOriginally posted by JeffB Quote
You can see in that great cut away above there is a huge gap between the back of the sensor and the nearest circuit board. Why does that gap need to exist or be so large?
That space is occupied by the IBIS system. Remember that cutaway does not show what is not at center.


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02-21-2015, 06:42 PM   #25
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QuoteOriginally posted by JeffB Quote
But my old film bodies had the film plane much further to the back so the overall depth of the camera body was less than any DSLR I've used.
Hmmmm...if that is generally the case, there may well be a reason.


Steve
02-21-2015, 07:23 PM - 1 Like   #26
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QuoteOriginally posted by shaolen Quote
No not the camera. I mean just all the internal electronics in general. The LCD the computer chips. Basically saying the circuit board in the DSLR could probably be made to be super thin along with everything else.[COLOR="Silver"]
My guess is the components in DSLR are probably manufactured with older process compared to cell phones. So sizes are going to be larger and heat dissipation won't be as good. Sure they can probably throw in cell phone quality components in there but we'd have to pay more for it. This is probably an area where a traditional camera maker like Pentax have a bit of disadvantage compared to electronics/camera maker like Samsung/Sony.
02-21-2015, 09:46 PM   #27
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QuoteOriginally posted by shaolen Quote
This also occurred to me after seeing the 645 cut away where they discovered all the empty space in it.
Just definitely do not look at a cutaway of the 645. A film insert was designed to be put deep within the body. (On my phone now and can't provide image links easily.)

The cutaway shown of the K-30 is more relevant. Yes, the area behind the sensor could be miniaturized further, but there is definitely not empty space.
02-21-2015, 10:49 PM   #28
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QuoteOriginally posted by filoxophy Quote
The cutaway shown of the K-30 is more relevant. Yes, the area behind the sensor could be miniaturized further, but there is definitely not empty space.
The patent drawings for the SR mechanism can probably be found and would show the unseen parts.
02-22-2015, 12:35 AM   #29
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QuoteOriginally posted by Not a Number Quote
The patent drawings for the SR mechanism can probably be found and would show the unseen parts.
Yes, the cutaway cameras are deceptive in that they only show the components and structure at the lens axis. Just a few days ago a PF user was puzzled that the meter cells were not visible in the 645Z cutaway. The same is true for the SR stuff. Stuff moves into and out of the "empty" space during normal operation.


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02-22-2015, 06:13 AM   #30
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QuoteOriginally posted by JeffB Quote
I have been asking this question for a long time and no one has ever provided a legitimate engineering or design answer. You can see in that great cut away above there is a huge gap between the back of the sensor and the nearest circuit board. Why does that gap need to exist or be so large?

The mirror box clearly consumes a majority of the mount to sensor/film plane distance. But my old film bodies had the film plane much further to the back so the overall depth of the camera body was less than any DSLR I've used.

Here are a couple interesting items from the manuals of the Nikon F100 and Pentax K-5II showing the difference in the location of the film/sensor plane.
Part of the issue is that film doesn't need anything at all behind it, except a light tight covering.

Saying that, if you could magically put the sensor, the important expensive part of the camera, in the same place as a film camera, with just the casing between it and the outside world, would you want to?
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