Is The Digital Tele-Converter Feature Worthwhile?

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bakubo
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Is The Digital Tele-Converter Feature Worthwhile?

Unread postby bakubo » Sat May 20, 2017 6:52 am

Recently I stumbled upon this write up from 2 years ago:

http://www.thewanderinglensman.com/2015/03/is-digital-tele-converter-feature-in.html

When I travel I always shoot raw, but in the last couple of years I have started to shoot jpeg quite a lot again when I am not traveling and just doing my daily wanders. Of course, we all know that these digital teleconverters just take a central crop and then interpolate it up to full size, but from playing around a bit with the one in my 20mp Olympus PEN-F and using the 75-300mm at 300mm it does pretty well. As a reminder, 300mm is 600mm in FF terms so with the 2x digital teleconverter that is 1200mm in FF terms! :!: Jeez, Louise!!! Pretty cool! :) In order to do a 2x conversion it needs to take the central 1/4 of the image (5mp) and interpolate that to 20mp.

20mp: 5184x3888
5mp: 2592x1944 (like the 5mp Minolta D7i I used to have)

The resulting 20mp jpeg looks pretty good, but on your computer if you reduce it back to 5mp it looks really good. Actually, just reducing it to 10mp or 12mp (4000x3000) also looks very good.

Shooting without using the digital teleconverter and then cropping on the computer (especially if using raw) and then resizing to 10mp, 12mp, or 20mp is similar, of course. Some in a discussion on another forum sometime back think that, at least Olympus, does a better job in camera, but I don't know. A really big advantage to using the digital teleconverter though is that the EVF shows what you will get at the proper size rather than trying to guess the central 1/4 of the image. You can see details better, see that things are in focus properly, etc.

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pakodominguez
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Re: Is The Digital Tele-Converter Feature Worthwhile?

Unread postby pakodominguez » Tue Jun 13, 2017 1:09 pm

Nokia/Microsoft are doing a good job on oversampling images (https://en.wikipedia.org/wiki/PureView). My Lumia 950 shoot 20MP DNG and 8MP jpg. If I zoom on the screen, the camera will give me a quite nice 8mp jpg, but the RAW file will be untouched (no zoomed raw).
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bakubo
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Re: Is The Digital Tele-Converter Feature Worthwhile?

Unread postby bakubo » Thu Jun 15, 2017 10:38 am

With my Olympus cameras using the DTC and RAW+JPEG then the jpeg file has the DTC applied, but, of course, the raw does not. If you shoot RAW and use DTC then the EVF shows the zoomed in view, but the raw is as always. You can see more clearly in the EVF what you intend to crop to later though.

I can certainly imagine that it is possible that Olympus and other companies could use the rawest raw (not just the raw data that makes it into a raw file, but even rawer data possibly) to do a very slightly better job of interpolating than software on a computer could do since it is usually working with demosaiced 16-bit or 8-bit RGB data. I don't know how Adobe ACR/LR do their enlarging. Are they using the raw data or the demosaiced data? Probably the demosaiced data. On a computer though there are many algorithms available for enlarging that can be experimented with. Anyway, I don't care much. Naturally, to get the best quality you are better off with a lens of the proper focal length, but for jpegs in some situations and also to play with a 1200mm equivalent lens it can sometimes be sort of fun. :)

Here are 2 recent ones at 1200mm equivalent using the 2x DTC and the Olympus 75-300mm at 300mm using the 20mp PEN-F and 16mp E-M10II. I don't present these as great photos and I wasn't trying to squeeze the best quality out of them. While playing around I had a few that were even better technically than these 2, but they were very uninteresting photos of uninteresting subjects (building walls, bushes, etc.) I had a UV protection filter on the lens, wide open, and handheld so several strikes against getting the best results. While we were in Kyoto for a month recently I was out on the 8th floor balcony of the furnished condo we rented and pointing to a street intersection some distance away. I think both of these are slightly cropped so maybe more like 1300mm or 1400mm equivalent. :lol: Resized to 10mp they still looked pretty good.

16mp E-M10II:

Image

20mp PEN-F:

Image

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bakubo
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Re: Is The Digital Tele-Converter Feature Worthwhile?

Unread postby bakubo » Mon Jun 19, 2017 7:02 am

bakubo wrote:With my Olympus cameras using the DTC and RAW+JPEG then the jpeg file has the DTC applied, but, of course, the raw does not. If you shoot RAW and use DTC then the EVF shows the zoomed in view, but the raw is as always. You can see more clearly in the EVF what you intend to crop to later though.


I discovered something else today. Not unexpected, but good to know in any case. Olympus meters using the zoomed in DTC portion, not the whole frame.

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Re: Is The Digital Tele-Converter Feature Worthwhile?

Unread postby Dusty » Fri Jul 14, 2017 5:06 pm

bakubo wrote:I discovered something else today. Not unexpected, but good to know in any case. Olympus meters using the zoomed in DTC portion, not the whole frame.


The one advantage of DTC. The disadvantage being that you don't get to play around with cropping formats, or different development algorithms outside what the camera gives you unless you also shoot RAW.

I basically find it useless, but YMMV!

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