1200mm: Digital Teleconverter

Started 7 months ago | Discussions thread
Eric Nepean
Eric Nepean Veteran Member • Posts: 5,655
Re: Downsizing?

boxerman wrote:

Henry Richardson wrote:

... I have found that if I then downsize the 20mp photo to 10-12mp on my computer it usually looks pretty darn good. For some images even the full 20mp looks good.

Why does the downsize look better, even sometimes? If there are no artifacts to average out, I don't know why the downsize would look better. (Except that sometimes you can/should sharpen higher res images more. People say that often enough for High Res mode on Olympus.)

I use DTC without fear in "emergencies," i.e., when the lens just doesn't have the reach. It's pretty much this, or lose the shot. Yes, you can crop in post, but it's much easier in-camera with other perks you get (more accurate metering and better view in the viewfinder.) I also suspect since the camera might do a little better than after-the-fact crop, but I can't offhand say why.

In JPEG  conversion, quite a lot of image fine detail is discarded. If you try to crop after JPEG conversion, the discarded information limits the acheivable resolution.

Noise reduction and sharpening also remove detail.

The camera can do its cropping anywhere the designer wants, and the most logical place for the designer to place a 2X or 4X crop is at the beginning of the image "pipeline" before any detail is discarded or obscured. The JPEG process also offers obvious tweaks or controls to discard less detail.

Many people speeculate that DTC involves interpolation after JPEG conversion and cropping (which is what the photographer is faced with). No system designer in their right mind would build something like this, its far more effective to crop first and not throw out as much image detail.

Here's a shot I got with my E-M5 (before pro-capture!), 75-300, DTC. Not suitable for large prints (as we often do), but nice enough to capture the moment I'll always remember.

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(Any image that I post in a DPR forum may be editted and posted in a DPR forum)

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