Originally posted by cyberjunkie The issue of converters vs cropping has been debated many times on this forum. My take is that outstanding lenses generally work very well with 1.4x converters, while average ones are better used at their sweet spot and the final image cropped as needed.
I've tip toed into this area without intending to. I went back through a bunch of shots I had done and put together this set of comparisons here - on this page, there are a few samples, and then a link to the full series on flikr:
question on tele conveter lenses - Page 2 - PentaxForums.com
I found part of the equation seemed to be the resolution of the sensor e.g. my K3II did about equal or maybe a nudge better to upsample and crop, but my K-1 did better with the 1.7x TC. I think the higher pixel density of the 24MP crop sensor with a high enough resolving lens can grab enough detail to upscale well. The equivalent 16MP crop of the K-1's sensor doesn't have as much granular detail to resize and upsample, so it's better off getting that 1.7x magnification optically on the front side, but the quality of the lens is crucial to what you get after that.
And thanks to everyone for their input on this and adding in the thoughts on TCs etc.