Cry for help - one-time shoot today spoiled due to mysterious blurring

[Maik Müller Menendez]

Nice test, thanks for posting. I wasn't fully aware that the complexity of a scene does affect the compression so much, i thought the files will just end up bigger when there are more details in a scene. Now it seems it's more a compromise between increasing file-size and getting softer. Good to know.

10:1 and so on will still be fine for less complex scenes, especially if your target is HD and/or the web... So don't panic.

Looking forward to your next test John, pretty girl shot on a prime sounds like a good setup for a compression-test. ;)

[Hannah Vinson]

How fast was your shutter? When we shoot in the studio we have a little bit less light, if we take down our shutter to much everything is soft. Can't get a good key on anything. Makes a huge difference as far my experience with poor focus.

[Dr. Sassi]

John,

fantastic examples, thank you.

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Martin,
I guess a sharper lens would increase the details and the amount of data needed to be compressed, with that: lower the image quality again based on the compression?
I never got that shooting for 2K delivery would be done with 2k resolution while recording, at least the RED website tells to capture 30% larger, which I do.
Noise is certainly an compression enemy as well.

Great stuff guys. Thanks for your help, suggestions and examples.
Can you also post some images from an identical test, using a better lens? Lot of people complain about the 24-70L, so i'd like to see the same shot with a prime!
Were the test pictures shot with the OLPF port bushing installed?


Thanks and kind regards,


Martin

[Blair S. Paulsen]

Tight crops of large frames are problematic for virtually any format south of 65mm so that might explain the test examples and be a contributor to the OP's issues.

As noted before any lens with an auto-focusing capability bears the risk of being inadvertantly switched into auto mode and then incorrectly choosing the background instead of the subject. If the metadata in the OP's clip shows focus at infinity rather than something like 15ft then its potentially the culprit.

I also wouldn't rule out mechanical issues with the focus ring on a mass produced lens, as noted previously as well.

My sympathies to the OP for the unfortunate timing of this issue, whatever it was.

Cheers - #19

[Peter Dmitriyev]

wow i must be blind cus op's shot looks sharp to me :(

[Gavin Greenwalt]

Looking at the R3D I see a few things:

1) Compression isn't magic. 6:1 has to throw away half of your information. That's fine when half of your information is useless (white wall). In this shot you have intense detail throughout the image (leaves) so the compression algorithm is going to simply make everything half as sharp.

2) Your lens is really soft. If you look at the bar next to the kneeling man there is about 4 pixels of chromatic aberration. If you run this through a CA correction it'll look a lot sharper. Shooting at 17mm is a surefire way to get an incredibly soft image.

3) In the first posted image there is also crazy motion blur. If you want to extract stills I recommend shooting less than 1/50th of a second.

[Martin Beek]

Thanks everyone for your advice, comments and tests. It has helped me a bunch!

I have sent the 24/70L in for service and received one on loan that is already much sharper.
The temp. replacement lens is OK up to aperture F6. Above that it becomes softer and softer.
The 17-55 is not bad at all, but only from F4 and up to F8 max. It's too soft at 17mm, but is OK from around 20.

Nevertheless, i was pleased to see (also after a few tests i did myself) that (more expensive) wide prime lenses also suffer from the same problem, in combination with compression.
Also i learned from my own tests NOT to expose to the right in these circumstances, but to keep it mediocre and aim for a nice "hunched" histogram.
Zooming-in and adjusting exposure to match 50-60% (zebra) on skin also works fine in several tests, and also using an incident light meter did help.

So, shooting wide with much detail: 800 ISO, don't expose to the right, keep aperture around the lens' sweetspot (use ND filter), choose a low compression ratio.

Thanks again and happy shooting ;-)

Martin