Regarding A700 vs. A900 Depth of Field

[a900_dw73]

Hi David,

Regarding your article, "Do you really need an A900?", if you use the APS-C crop mode feature of the A900, where it shoots in 11mp mode, would the Depth of Field characteristics then match the A700, but with 11mp vs. 12mp ?

In other words, in the 11mp crop mode of the A900, does it use the 16X24mm center of the 24X36 "Full Frame" ? And, in doing so, does it in essence give you a 2nd camera in one? But, it's hard to frame the shot with the crop mode on, because you have to kind of judge where the corners are in the A900 Viewfinder, right?

Lastly, I think the A900 has slightly larger pixels - I think it was 5.9 microns vs. 5.7 microns in the A700? So, does that mean if you were to crop the same exact part of the frame on the A900 which would match the A700 size sensor, does the A700 technically have ever so slightly higher "resolution" because the pixels are a bit smaller - barely more packed into the same shape/size? This is probably trivial because it's splitting hairs - the better "resolution" comparison is probably the A900 vs. the Nikon D700 - 24 vs. 12 on the same sized sensor.

Apologies if any of this is trivial or meandering, but I was just wondering if it's possible, or makes sense that you can use your A900 as an APS-C style camera with the same depth of field characteristics - can you say you get two cameras in one? Or, better yet - is there a way I can test this? Similar to how you said a shot on the A700 can give you a faster shutter speed compared to the A900, in terms of getting an F8 depth of field (vs. having to shoot F13 on the A900) - in other words, if you turn crop mode On on the A900, can you get the same depth of field at F8 as on the A700?

Dave

[David Kilpatrick]

Assuming you use the same angle of view, all of what you say applies. That is, you must use and 18mm lens on the crop mode where you would use a 28mm on full frame. If you just crop, and effectively enlarge part of the 900 frame for a print, you will get less depth of field not more. There are markings in the finder but they are very faint. You certainly can use the 900/850 in crop mode and the results are identical to an 11 megapixel APS-C camera, so long as the lens used is also identical.

David

[a900_dw73]

I guess my last question would be: what percentage of the A900 viewfinder is used in the crop mode? And, is it even worth using the crop mode, in practice that is?

Sometimes I miss my good ole A700, and I'm just curious if I can "get away" with saying that I "shouldn't" because the A900 could become an 11mp crop mode camera if it was absolutely needed, albeit with more difficult framing with the huge ViewFinder.

Dave

[David Kilpatrick]

Really there is no point in using the crop mode unless you have issues with card space and storage. You don't get any faster than 5fps, and you don't get faster writing to and through the buffer, or a longer burst of continuous shooting. Full frame already provides maximum on all this.

Plus, if you are following action - say birds - then just use full frame. How many action shots are missed or marred by poor framing, badly centered, bit of subject cut off? Just use full frame, and get the ability to crop your shot, with extra room for the subject to be 'not perfectly centered' when you fire the shutter.

David