1200mm: Digital Teleconverter

Started 8 months ago | Discussions thread
boxerman Senior Member • Posts: 1,808
Re: Downsizing?

Thanks for responding and also cultivating this thread.

But, I'm still puzzled, if you're inordinately patient:

Henry Richardson wrote:

boxerman wrote:

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.

DTC interpolates 5mp to 20mp. In other words, 1 pixel becomes 4 pixels. If you downsize to 10mp then 1 pixel becomes 2 pixels. In your photo editing software on your computer I suggest you uprez a photo:

  1. 2 times the pixels
  2. 4 times the pixels
  3. 8 times the pixels

Take a look at each of them at 100%.

I don't need to do this experiment as the outcome is obvious. At 100% you see each pixel, so of course you'll see smearing from spreading out one pixel to N. Artifacts also get bigger, so more noticeable.

The fairer experiment is to view uprezes all at the same largish size, near your intended output medium (possibly corrected for the viewing distance--people want very large prints to resolve what they'd see from a foot away; silly. Who inspects a 1-2 meter print from that close?).

In short, viewing at 100% is unfair to higher-resolution images, which get MORE enlargement by the process than lower resolution. In the end, I will display or print at the same size as I want for each image.

I think people make the same mistake about noise. Panic with individual pixel noise. But, if you have a high-resolution image, your eye will effectively average noise across AREAS, not pixels.

But, even if this were a demonstration, I'm still after the "why."  In my comment above, I understand small pixel clusters being effectively averaged by your eye, with it's limited resolution. I understand that PIXEL noise will get reduced by averaging in down-rezing, but again, that might not be perceived noise, at some standard output size and distance.

Also, see this:


I did, thanks.

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.

Yeah, and it is fun too. Especially for out of this world focal lengths like 1200mm-efl!

Oh, I forgot to mention before: I put DTC on a button. I put it on my video (orange) button, since I rarely use video and, when I do, can trouble to twirl the knob. That way, it's basically instant to use.

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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The BoxerMan

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