Originally posted by G_Money In your opinion does optical cropping become less desirable if the image is destined for print? If your printer required a minimum of say 200ppi then a K-5's resolution of 4928 pixels (long edge) would give a print of 24.6 inches. Without resorting to image resampling, a 1.4X crop would only allow a print of 17.6 inches. To get back to the 24.6 inch print, do you think resampling would be better or worse than optical cropping using the full resolution?
I don't think there is a clear answer to the question. There are a whole series of trade offs many of which are not under your control that I think
drive the decision.
The best way to screw up a photo is to get it out of focus. the object of your affection needs to be both big enough and bright enough in the viewfinder for you to get the focus 'right on'. This is vastly more difficult with the A*600 than with thte A*400. While bigger and brighter are reciprocial, If the object isn't big enough to see, brighter doesn't matter. This consideration tilts to optical cropping unless the lighting is really difficult.
Another way to screw up a photo is to get the exposure really bad. While the instant review is helpful, around here the dominant 'background' is
a very dark green douglas fir tree. If this 'background' dominates the scene it will burn out the foreground target. While this can be mitigated some using single point exposure option, the point is that extraneous lighting conditions can cause a lot of grief which can be mitigated with optical cropping.
Conversely, If you are trying to take a picture of a moving target...... leaves fluttering, animals moving, birds that may fly away, while you are trying to bolt your camera to a block of concrete so it won't vibrate, take the picture and fix it in photoshop.
Composition is much easier in photoshop. You can drag the crop lines around to your satisfaction. Something you can't change if you do 'incamera' cropping. Also the converter effectively magnifies any optical imperfections. If use one, edge fall off can be expected,
but can be mitigated by 'stopping down'. Strong lighting conditions can be expected to greatly improve optical cropping results.
I should mention that I exclusivelyl use RAW images for what I've done here. The JPG compression of necessity tosses some detail, and since large hard drives and large memory cards are cheap, There is no excuse for stuffing 10 lbs of stuff in a 5 pound bag as the JPG algorithm does
until you have decided on what the final composition should be.
I can go no further than say that the optical converter is not a free lunch. the cropping that it accomlishes optically leaves less that you can do
digitally. They are reciprocials, but like trading f stops for shutter speed, there are a whole hose of external reasons for pushing the envelope one way or the other.
What I actually set out in this thread to do was explore whether owning both a A*400 f2.8 and an A*600 f5.6 made any sense at all.
Superficailly it would seem that you can slap a 1.4x converter on the A*400, or the 1.7x adapter,and have and effective focal length
similar to the 600, and perhaps have some speed to spare. Were that always the case, owning both would be pointless.
It turns out not to be the case. While the A*400 f2/8 is probably the most impressive optic that I have ever had my hands on, and even though
I've owned its baby brother, the A*300 f2/8 for a decade or more, the 400 continues to impress me with its abilities--and it's not just the focal length I've owned a couple different 'slow' 400's and have disgarded them. I've got for example a SIGMA 400 f5.6 that is auto focus, but I haven't put it on the camera in years because the buzz isn't there.
But as unique as the A*400 is, It isn't a 600, and when the 600 gets in its element--- (enough light that the f5.6 limitation doesn't cripple it), the best 400 in the world won't keep up.
Not a solid answer here, but I would look real hard at the lighting when setting up for the photo. Reallly strong lighting and nothing moving (neither the target nor the camera) are the best for optical cropping, but if you have weak light and a strong gusting crosswind....