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09-29-2013, 05:14 PM   #61
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The FA and earlier K mount telephotos were full frame. I have a sigma telephoto that is full frame. K mount was a full frame film mount for decades. The SR may be an issue, I'm certain all of us have lenses that work on a film body, hence full frame. The DA560 was designed for aps-c sensors, so isn't full frame. Lens design, not mount design.

Those A telephotos and teleconverters with the lens element protruding into the body worked on film.

09-29-2013, 05:44 PM   #62
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QuoteOriginally posted by derekkite Quote
..The DA560 was designed for aps-c sensors, so isn't full frame. Lens design, not mount design.
.
To correct you, DA560 works okay of Pentax film cameras. Shows some vignetting wide open, which disappears later when stopping down.
It's the same behavior found in many Nikon's and Canon's long telephoto lenses.
Thus I presume we can say DA560 will be usable on an FF digital camera from Pentax, but will work best on APS-C DSLR. It doesn't have that extra FF 'oomph' that would make it even bigger, and most likely, more expensive.
09-29-2013, 06:10 PM   #63
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QuoteOriginally posted by Pentaxosaurus Quote
Don't know what you call “normal image stabilization”. The Pentax APS-C sensors can move by ± 1 to 1.5mm; a larger format needs larger movements as the same field of view is projected onto a larger area. Therefore the pixel movement is amplified by the crop factor and, accordingly, the sensor has to move more for the same effect: ± 1.5 to 2mm.

It's somewhat unfortunate that a larger sensor, which is heavier anyway, needs larger movements, and explains why there is no IBSR for the 645 format (although the lenses do cover a large image circle of about 75mm while the sensor only measures 55mm diagonally).

I really don't want to spoil the fun, but we shouldn't entertain any hopes that Pentax can do anything that is physically impossible. And whine if they don't.
Not that I want to cut you off, but we've been down this particular rabbit hole several times over, here, and there are two schools of thought, one of which agrees with you, and the other doesn't. The former says (as you do) that the sensor moves a certain amount, and therefore all (or, maybe, most) of that movement is required for image stabilisation, while the other says that it's only been shown (by Falk Lumo - google his website, if you want to see more) that a few pixels are required for it, with the rest of the movement being taken up with acceleration and deceleration phases for the IBIS function. Of course, the full movement is exploited for the astro-tracking function with the GPS unit.

However, without engineering proof either way, we're all only speculating. Not that speculation isn't popular around here...
09-29-2013, 07:10 PM   #64
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QuoteOriginally posted by Mistral75 Quote
Not that thinner, except for the grip.
From the other side, yeah it's the grip (and the popup flash) and probably around 2~3cm thicker than the K-5.

Still can't get over the round design of the top LCD though. It looks outworldly (though personally I think it looks cool) and uhm, very late-90's. I wonder if Pentax will ever keep anything from this prototype...

09-29-2013, 10:19 PM   #65
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QuoteOriginally posted by Alizarine Quote
(...)
Still can't get over the round design of the top LCD though. It looks outworldly (though personally I think it looks cool) and uhm, very late-90's. I wonder if Pentax will ever keep anything from this prototype...
They kept plenty, including the round top LCD, fo the MZ-S .

09-29-2013, 10:35 PM   #66
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How on earth can anyone understand the translated text?
09-29-2013, 11:34 PM   #67
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QuoteOriginally posted by Pentaxosaurus Quote
Don't know what you call “normal image stabilization”. The Pentax APS-C sensors can move by ± 1 to 1.5mm; a larger format needs larger movements as the same field of view is projected onto a larger area. Therefore the pixel movement is amplified by the crop factor and, accordingly, the sensor has to move more for the same effect: ± 1.5 to 2mm.

It's somewhat unfortunate that a larger sensor, which is heavier anyway, needs larger movements, and explains why there is no IBSR for the 645 format (although the lenses do cover a large image circle of about 75mm while the sensor only measures 55mm diagonally).

I really don't want to spoil the fun, but we shouldn't entertain any hopes that Pentax can do anything that is physically impossible. And whine if they don't.
My tests show that 4 stops SR require ~ +-0,2 mm movement for APS-C, so +-0.5 mm should be enough for FF.
It not very hard to test. All you need to do it check how much blur you get when using 4 stops longer shutter speed then you can get sharp images when hand held.

When tested on my K7 I got ~75 pixels blur for 4 stops slower shutter speed, which is less than +-0,2 mm, and even when using several seconds shutter speed blur never got more than 150-200 pixels (+- 0.4-0.5 mm).

Last edited by Fogel70; 09-30-2013 at 12:30 AM.
09-30-2013, 12:28 AM   #68
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QuoteOriginally posted by Mistral75 Quote
They kept plenty, including the round top LCD, fo the MZ-S .
Can't say I'm a fan of the hunchback look of the MZ-S/D, and the tiny LCD would be close to useless for presenting the information that's on our current crop of DSLRs. Anyway, that 1980s/90s cool won't be fashionably retro for at least another 10 years.

09-30-2013, 12:35 AM   #69
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QuoteOriginally posted by Fogel70 Quote
My tests show that 4 stops SR require ~ +-0,2 mm movement for APS-C, so +-0.5 mm should be enough for FF.
It not very hard to test. All you need to do it check how much blur you get when using 4 stops longer shutter speed then you can get sharp images when hand held.

When tested on my K7 I got ~75 pixels blur for 4 stops slower shutter speed, which is less than +-0,2 mm, and even when using several seconds shutter speed blur never got more than 150-200 pixels (+- 0.4-0.5 mm).
Maybe I'm looking at it incorrectly, but surely the crop factor doesn't enter into the amount of sensor movement for a given blur reduction, when the FL and distance from the flange to the sensor plane are identical. I really should sit down and look at the optics involved. No doubt someone will, if only to refute that assertion.
09-30-2013, 02:17 AM   #70
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QuoteOriginally posted by RobA_Oz Quote
Maybe I'm looking at it incorrectly, but surely the crop factor doesn't enter into the amount of sensor movement for a given blur reduction, when the FL and distance from the flange to the sensor plane are identical. I really should sit down and look at the optics involved. No doubt someone will, if only to refute that assertion.
It all depends on how much blur you can accept as a sharp image and the amount of pixels you got. With more pixels you get more pixel blur with the same amount of camera shake.

Using APS-C and FF with same pixel count, FF will require 1.5x more sensor movement for the same amount of pixel blur reduction. By using same focal length on both will require 1.5x faster shutter speed on APS-C as FOV are different.

If using smaller pixels on FF and if you require same amount of pixel blur reduction on both, the difference in movement of the sensor get smaller until it gets the same when pixel size is the same. And with smaller pixels you are going to need faster shutter speed when hand holding the camera to take full advantage of the higher pixel count.

But with more pixels on FF you might accept more pixel blur on the final image, depending on what you are going to use it for.
09-30-2013, 05:10 AM   #71
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QuoteOriginally posted by Mistral75 Quote
(...)

Do you realize that the Asahiflex mount had an EXTERNAL diameter of 37mm whilst being a 24x36 mount?
QuoteOriginally posted by Pentaxosaurus Quote
(...)

And what lenses did they have? Focal length, max aperture??

(...)
  • 50mm f/3.5 (Tessar type)
  • 58mm f/2.4 (fastest Heliar type standard lens ever)
  • 83mm f/1.9 (Sonnar type but with split rear group)
  • 100mm f/3.5 (Triotar type)
  • 135mm f/3.5 (telephoto type)
  • 500mm f/5 (long lens)
All launched over four years. Not bad, eh?

Another example of a 24x36 mount, the diameter of which is (much) smaller than 43mm: Leica thread mount also called LTM or L39 since the external diameter is 39mm. A few lenses (Leica and Voigtländer):
  • 12mm f/5.6
  • 15mm f/4.5
  • 21mm f/4
  • 25mm f/4
  • 28mm f/3.5
  • 35mm f/1.2
  • 50mm f/1.4
  • 73mm f/1.9
  • 85mm f/1.5
  • 90mm f/2
  • 125mm f/2.5
  • 135mm f/4
  • 180mm f/2.8
  • 200mm f/4
  • 280mm f/4.8
  • 400mm f/5
  • 560mm f/5.6
  • 800mm f/6.3
09-30-2013, 05:17 AM   #72
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QuoteOriginally posted by MouLaG Ôfr Quote
Certainly not, it was an early prototype destined to be marketed.
But Pentax decided not to do so (and it's difficult to blame them, Contax, with the same sensor, tried to do it but it ended with a cessation of activities in 2005 ! This was to early for the digital market to release a FF camera.)
(...)
Put the blame on the Philips sensor. Pentax abandoned work on the MZ-D prototype in late 2001. The Contax N Digital began to be sold in spring 2002, after several delays. The Canon EOS-1Ds of late 2002 was a success.
09-30-2013, 09:41 AM   #73
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QuoteOriginally posted by RobA_Oz Quote
Not that I want to cut you off, but we've been down this particular rabbit hole several times over, here, and there are two schools of thought, one of which agrees with you, and the other doesn't. The former says (as you do) that the sensor moves a certain amount, and therefore all (or, maybe, most) of that movement is required for image stabilisation, while the other says that it's only been shown (by Falk Lumo - google his website, if you want to see more) that a few pixels are required for it, with the rest of the movement being taken up with acceleration and deceleration phases for the IBIS function. Of course, the full movement is exploited for the astro-tracking function with the GPS unit.

However, without engineering proof either way, we're all only speculating. Not that speculation isn't popular around here...

Plus, SR can be turned off for use on tripods etc.
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