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02-10-2012, 11:58 AM   #1
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Any other benefits to XS lens back elements being closer to K-01 Sensor?

Or inherent disadvantages?

The decision to use the K-mount with a thicker body made a lot more sense to me when I saw the picture of the new XS mystery lens that showed the back element that would extend into the K-01 body. By doing this, the part of the lens that sticks out in front of the camera could be smaller. One mount, advantage both ways!

I'm not good with the science of lenses, so my question is, does this lessened rear element to sensor difference have any other advantages, or dis-advantages? Does it affect relative depth of field for example?

If an XS specific 18-55 would be built, would the front element to back depth have to be the same?

02-10-2012, 12:10 PM   #2

Join Date: Jan 2012
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I think the closer you go to the sensor with the lens, the more severe the angle of light hitting the edges of the sensor will be. This has got to impose some kinds of limitations/problems for the designers as far as maintaining image quality goes..... I think Pentax has the unique ability to "Tune" the register distance for each new lens they produce for the k-01 which means I expect the Pentax system is gonna kick the crap out of the competition when it comes to edge to edge sharpness and vinetting.

What I mean specifically is this... Pentax can recess the rear element as close or as far from the sensor as they need to to find a "Sweet spot" in image quality for each new lens.. Sony cannot... this may in fact explain why Sony lenses are so huge... if they need space between the rear element and the sensor, they have to build that into the lens.
02-10-2012, 12:24 PM   #3
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Leica has issues with this. Most of their lenses get very close to the film, which tends to cause a red tint around the edge of the image. They do a lot of microlenses and other fun tricks to try and minimize it, but to my knowledge it's just a physical property that the sensor can pick up the longer wavelength better at high incidence angles.

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