mickporter said:
"The improvement in sharpness from 4 to 6mp is, I am reliably informed via the Yahoo digiscoping forum, significantly less than might be expected."
They are lying mate...... There is a huge difference. Just compare the difference between the Nikon and your Fuji 602, and that camera is interpolated upto 6M and not a true 6 megapixel.
"Huge difference" and "significantly less than might be suspected" are pretty vague references. So lets be a bit more precise.
A CP995 at 3.1MP has a 2048x1536 pixel image. Moving to a CP4500 (which is actually a bit less than 4MP) adds about 25% more pixels, but increases the linear resolution only about 10% (2048 increases to 2272). So your 8x10 image might be enlarged to 8.8x11 with no noticable decrease in quality. As you go up the scale, a 1MP increase means less and less as a percentage increase in linear resolution.
Most cameras used for digiscoping have smallish sensors that use typical Bayer type CCD sensors. If the sensor type changes in a significant way, then a simple look at the numbers may not be sufficient. The Fuji 602 uses a different sensor design. It gets a bit better performance out of its 3MP sensor. By my eye and the tests done at DPreview.com, its better than the typical 3MP and not quite up to the quality level of a typical 4MP camera.
There are other sensor designs as well. The Foveon is only a 3MP sensor, but it performs almost as well as a 6MP DSLR sensor since it lacks the Bayer mask. And the larger sensors on a 6MP DLSR sensor have lower noise than the smaller sensors on the typical digicam used for digiscoping.
mickporter said:
I suppose record shots of birds taken by digiscoping probably is not going to show much improvement. The time taken for the camera to save pictures of that size would not be suitable for this hobby. But any more serious photography and it makes a huge difference in the outputted pictures on the printer.
I regularly shoot at 5MP and can fire off a sequence of 7 images non-stop. I don't see how shooting at 6MP - a mere 20% increase in data - should present much of a problem if the camera is designed to quickly process that size of an image.
mickporter said:
The other factor is that DSLR's or top of the range big megapixel cameras usually also output in RAW format, which means there is no loss in picture quality by compression. No serious photographer would use anything less when doing wedding photographs or portraits etc.......
Now the time required to write a RAW file might very well slow down the camera to the point of crippling it for wildlife photography. I think the DLSRs do manage to write RAW files a bit faster.
Anyway folks, what makes a "huge difference" or what is "significantly less than might be expected" is certainly open to different interpretations. I suggest that anyone interested in the topic should take the time and interpret for themselves with their own eyes. Download original unaltered files from DPreview.com or similar sites that keep such examples. Then print them or have them printed and decide for yourself with your eyes. That is precisely what I did when I moved from a 3MP to a 5MP. The difference was not dramatic IMO, but it was noticable to me and I decided that, for me, it was worth the expense. In fact, a friend prefered the 3MP image that I printed - which makes the point that the content of the image has a huge impact on how well it can tolerate being enlarged - even when images have as large a gap as that between 3MP and 5MP.
Of course, this is only speaks to the camera when used normally. Digiscoping brings another set of questions and issues into the discussion. For instance, sensors with greater resolution reach the limit of the scope's magnification sooner.
