D7100 vs. 1.4x Teleconverter for wildlife photography

Started Feb 23, 2013 | Questions thread
OP bugbot42 New Member • Posts: 24
Re: Not quite mosswings...

JimPearce wrote:

The real baseline test of a teleconverter is "Is it better than cropping?", and on the 300 f4 it is much better than cropping.

Jim: With regards to a resolution drop when cropping vs. using a teleconverter, I believe it isn't applicable in this case. When photozone talks about the quality of cropping vs. TC, they're using the same camera as they are when using the TC, which means far fewer megapixels when cropping and thus a lower resolution. In the case of the D7100 cropped vs. a D90+1.4TC, a crop to the same field of view using the D7100 actually yields more megapixels than the D90+1.4TC, and likely a higher resolution with no drop in quality (due to not adding any glass in front of the sensor). This would seem to indicate that better results would be achieved with a D7100 and no TC than a D90+1.4TC.

Mattr: I don't believe you lose a any light from cropping. The total amount of light hitting the sensor (or in this case, the part of the sensor used) is reduced, but the same amount of light per area hits the sensor, so there's no effective loss of light. You're definitely right about the magnification in the viewfinder being better with a TC, and I'm a little concerned about how that effects the focus points. The focus points stay the same size when cropping, so they cover a larger portion of the field of view. When using a TC the image is magnified prior to hitting the sensor and autofocus sensors, so the autofocus points cover a smaller part of the subject, likely providing a more accurate focus. For instance, if I took a picture of a heron without a TC, the autofocus point might cover most of the head, and I might not get the eye sharply in focus. With a TC, the autofocus point would cover a smaller part of the head, and I'd be able to more accurately select the eye to be focused on.

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