Sensor crop desires - discussion

Started Oct 23, 2007 | Discussions thread
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Lance B
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Sensor crop desires - discussion
Oct 23, 2007

There is a push by the market and the desires of many photography enthusiasts to have a larger sensor than the APS C sensor. FF is considered the "Holy Grail" by many, but is it really neccessary?

If you could have a sensor size anywhere between APS C - 23.5mm x 15.7mm and "FF" - 36mm x 24mm, what would you choose? Bearing in mind that I do not think Pentax could implement SR on a FF sensor as I do not think there would be enough room inside the image circle of legacy 35mm lenses to allow for the movement of the sensor for SR although there is conjecture over this point so I could be wrong on this point. Do not forget that SR on FF may still allow for movement inside the image circle, but then light fall off etc also becomes a factor once the sensor moves from it's optimal location.

If SR cannot be implemented on a FF sensored camera, than SR lenses would have to be developed which maybe a cost burden that many may not like and could further hamper Pentax's lens development and push it back even further. A "mid range" crop maybe the interim answer. Many or most of us could still carry on with our lenses without having to upgrade too many of them. APS C can still be sold along side the new crop factor as well, so we can keep using many of the APS C only lenses if desired. As we all have APS C cameras now, we could even use those cameras for wide angle applications until we purchased wide angle lenses, but this is may not be such a burden as many of our current lenses become wider than on APS C.

Another benefit is that many of the DA lenses may still work on a 1.2x, 1.25x or 1.3x crop sensor and thus we would not have to sacrifice our entire DA lens line-up for the new crop. The only lenses that would not work would be the DA14, DA16-45, DA18-55, DA12-24 and the DA10-17. Other's may still work, but I do not know.

My personal desire would be for a 1.25x crop factor or a 28.8mm x 19.2mm sensor or a 1.3x crop 27.7mm x 18.5mm sensor. Maybe even a 1.2x crop at 30mm x 20mm sensor.

Our FA lens FF equivalent for 1.20x crop would be:
FA20 = 24mm
FA24 = 29mm
FA31 = 37mm
FA43 = 52mm
FA50 = 60mm
FA77 = 92mm
FA85 = 102mm
FA100(macro) = 120mm
FA135 = 162mm
FA200 = 240mm
FA300 = 360mm
FA28-70 = 34mm - 84mm
FA80-200 = 96mm - 240mm
etc

Our FA lens FF equivalent for 1.25x crop would be:
FA20 = 25mm
FA24 = 30mm
FA31 = 39mm
FA43 = 54mm
FA50 = 62.5mm
FA77 = 96mm
FA85 = 106mm
FA100(macro) = 125mm
FA135 = 169mm
FA200 = 250mm
FA300 = 375mm
FA28-70 = 35mm - 88mm
FA80-200 = 100mm - 250mm
etc

Our FA lens FF equivalent for 1.3x crop would be:
FA20 = 26mm
FA24 = 31mm
FA31 = 40mm
FA43 = 56mm
FA50 = 65mm
FA77 = 100mm
FA85 = 110mm
FA100(macro) = 130mm
FA135mm = 175mm
FA200 = 260mm
FA300 = 390mm
FA28-70 = 36mm - 91mm
FA80-200 = 104mm - 260mm
etc

Also, we have to remember that focal lengths are rather arbitary except for what would be considered the "standard" lens focal length and for a 1.2x crop that would be possibly the FA43 @ 52mm. For 1.25x crop that would be either the FA31 or FA43. For the 1.3x crop that would again be the FA31 or the FA43 again. Maybe the DA40 could be used for any of these crop factors 1.2x = 48mm, 1.25x = 50mm and 1.3x = 52mm. All other focal lengths are just that, focal lengths, and we would get used to their new angles of view. I mean, when we use a zoom, we are quite happy to use any focal length between the two extremes, so we should be quite happy with their new found angles of view on another sensor size.

Other benefits are that any of the crop factors outlined would be:
1) less costly than FF.
2) The benefit of FF over any of these crops would be very marginal at best.
3) Pentax can still use SR? If this is true this could be a major factor.
4) Still a benefit over FF for longer focal lengths due to the crop.

5) Wide angle lenses may become smaller as they are really quite big for the 1.5x crop when compared to FF wide angle lenses.

6) Less DOF where required with the same aperture. This obviously can also be a negative for some, but diffraction is lessened, so you can stop down futher than with a 1.5x crop.

With the benefits outlined above, for every gain there is a loss, so it comes down to a compromise. My personal desire is for the 1.25x or 1.3x crop as this is a good compromise over FF. Taking into account the above facts, what would be your desire?

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Lance B
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