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06-04-2008, 12:50 AM   #181
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No, IMO another crop would be a mistake. Either keep 1.5 or go FF.

06-04-2008, 04:12 AM   #182
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K mount fine with FF and SR

QuoteOriginally posted by thibs Quote
No, IMO another crop would be a mistake. Either keep 1.5 or go FF.
I agree.

Also, SR should be possible with the current mount and FF.

The K mount register distance is 45.46 millimeters (same as M42), its unobstructed diameter 44.8 mm, its obstructed diameter 47.8 mm, and FF diameter 43.27 mm.

The K mount was specifically designed for FF and fast lenses up to f/1.2. I see no problem to have this mount with FF and SR. Maybe, the outer corners see slight extra vignetting during SR with some lenses but still should be fine.

It is an advantage, actually, because it makes compact FF DSLR possible/likely other vendors would have a hard time to counter.

The recent addition of the SDM contact is obstructing the mount diameter to less than 40mm. However, these are old FF lens power zoom contacts actually not creating extra obstruction for an FF sensor as they are moved slightly off the corners. It shows the headroom of the K mount.

Still, I guess that with FF/SR in mind, the SDM contacts would have been positioned different from the old power zoom contacts. They are now the mount's weakest point when it comes to FF/SR. But fortunately, there officially aren't any FF SDM lenses and maybe, there never will.


I deleted the above paragraph. I checked it out in detail and the SDM contacts are not causing an issue. I've created a drawing to verify this, cf. attachement.

The drawing is based on Bojidar Dimitrov's great Pentax K-Mount Page Features and Operation of the Kaf2 Mount

Last edited by falconeye; 06-15-2011 at 05:28 AM.
06-04-2008, 05:55 AM   #183
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What about a FF with 1.3 and 1.5 cropping capabilities? You would have FF w/o SR; 1.3x with SR and 1.5x with SR and DA compatibility. They can keep the mount and then they can start releasing slowly a new mount for FF SR. On the other side, I would be surprised if Hoya were pro-backwards compatibility
06-04-2008, 08:52 AM   #184
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This is why I said 1.3 crop, most of the DA lenses will fill the 1.3 crop with no problems or IQ looss vs a FF, we will get to keep SR and lens compatability! the cost difference also will not be as much as FF for sensor production. It is actually easier to do and cost effective. We wil have a real D300 / 5D replacement killer and even if the noise is the same, the extra 2 mp wil more than make up for it and justify a higher price tag over the K20D. IT will be a step in the right direction at least.

06-08-2008, 03:56 AM   #185
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QuoteOriginally posted by ftpaddict Quote
Ok so most DA glass is full-frame.
The latest DA* primes (200 & 300) are full-frame, because they're derived from the FA* versions. Same goes for other DA lenses.
The DA Star 200 f/2.8 has the same optical design as the FA Star 200 f/2.8.
But that is the only one.
The DA Star 300 is not a DA version of the FA Star 300, it uses a new optical design. Same goes for other DA lenses.

The wide angle DA's and the wide angle DA zooms and standard zooms are not 24x36.
The telephotos seems to be 24x36.

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