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09-13-2013, 10:31 AM   #31
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QuoteOriginally posted by Rondec Quote
Do you really think that? "Sensor size determines NOTHING?" Obviously on a k mount camera, with the same register distance, there will be limitations to the size of the lens, but certainly for a DA 70 limited to be full frame compatible, it would have to be bigger than it currently is. Same with the DA 40 and the DA 35 limiteds.
No actually it would not. While it may get heavier with some larger internal elements if the design could not project from its current rear element over the bigger image circle, but once you are past the system regestry distance in focal length such that retro focus lenses are not used. It is the front element and aperture value that really determine size. With the DA 70 it is relatively slow at F2.4. This means the front element only needs to be about 28mm in diameter. This is smaller than the bore diameter of the K mount so the bore diameter actually defines the size nothing else. You could increase the diameter quite a bit before the front element (which determines speed) comes into play.

As for the DA 40 look at the M40 What makes some of the DA lenses so small is deletion of the aperture ring. TheM40 is only 19mm long compared to the DA40 at 15mm

The DA 35 mm is an F2.8 lens so it is one stop slower than the M35/2 but the DA is 10 grams heavier, and 4 mm longer

As I said, full frame is not a size driver! That is an absolute myth.

What drives the canon and Nikon less size is a mystery partially. They just don't need to be as big as they are


Last edited by Lowell Goudge; 09-13-2013 at 10:40 AM.
09-13-2013, 11:09 AM   #32
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QuoteOriginally posted by Lowell Goudge Quote
No actually it would not. While it may get heavier with some larger internal elements if the design could not project from its current rear element over the bigger image circle, but once you are past the system regestry distance in focal length such that retro focus lenses are not used. It is the front element and aperture value that really determine size. With the DA 70 it is relatively slow at F2.4. This means the front element only needs to be about 28mm in diameter. This is smaller than the bore diameter of the K mount so the bore diameter actually defines the size nothing else. You could increase the diameter quite a bit before the front element (which determines speed) comes into play.

As for the DA 40 look at the M40 What makes some of the DA lenses so small is deletion of the aperture ring. TheM40 is only 19mm long compared to the DA40 at 15mm

The DA 35 mm is an F2.8 lens so it is one stop slower than the M35/2 but the DA is 10 grams heavier, and 4 mm longer

As I said, full frame is not a size driver! That is an absolute myth.

What drives the canon and Nikon less size is a mystery partially. They just don't need to be as big as they are
Well, I would respectfully disagree. I think that Pentax set limits on the "smallness" of their lenses when they chose to keep the k mount. If they had chosen a shorter registration distance, a smaller mount opening, the size of the lenses could definitely have been smaller. Hence the reason why micro four thirds lenses are so much smaller for what they are than Pentax lenses.
09-13-2013, 12:54 PM   #33
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QuoteOriginally posted by Rondec Quote
Well, I would respectfully disagree. I think that Pentax set limits on the "smallness" of their lenses when they chose to keep the k mount. If they had chosen a shorter registration distance, a smaller mount opening, the size of the lenses could definitely have been smaller. Hence the reason why micro four thirds lenses are so much smaller for what they are than Pentax lenses.
That is not a disagreement, I said all along one of the limiting factors was the KMount. As for registration distance, that does nothing to change the real size of a 200/2.8 lens. It still needs a 77 mm filter.

What makes micro 4/3 lenses smaller is that you don't need the same focal length for an equal field of view, so an effective tele lens ( when viewed from FOV of 35mm equivalent is 33% smaller than for APS-C and 50% smaller than for full frame

Lets compare apples and apples here please. In fact a micro 4/3 lens with identical optics will be longer than a similar lens for PK mount only because the lens barrel needs to be longer to make up for the shorter registration distance

One benefit micro 4/3 has is that you need to be much shorter focal lengths before you get into retro focus lenses so for things in the 30 mm range the optical design is simpler...but also remember for a 4/3 lens you need to get wider for same GOV and some ultra wides are pretty big and very expensive
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