Soft focus issue

[Yousuf Abbasi]

I recorded some footage this weekend, brought the R3D's into Premiere Pro, and noticed the images were soft. None of the areas in focus were SHARP like they should be, there was almost like a very soft blur over the image. I don't think it's a backfocus issue because I recently had the backfocus set (but it could be).

The images were soft on both 50mm and 85mm Zeiss (superspeed) primes at T1.3. The room had limited lighting so thats why the aperture was set wide open.

When I use the "Sharpen" tool in Premiere, the focus looks a lot better BUT the downside is it adds a lot of noise to the picture.

Any idea what's causing this issue? (I have a guess).

[David Mullen ASC]

Well, one reason is that Zeiss Super-Speeds fall-off dramatically in sharpness somewhere at the f/2.0-2.8 split area. Combine that with the fact that it's very hard to follow-focus at f/1.3 so missed-focus is commonplace.

[Hans von Sonntag]

I have SuperSpeeds and use these lenses over 20 years now. Although they are considered to be soft until T2.8 they are sharp if we talk about focus. Shooting at T1.4 is a challenge and leads often to soft pictures, the depth of field is hardcore shallow.

If you think that your backfocus is off, slap on a freshly serviced 18mm, open the iris to T 1.4 and point it to a chart or a newspaper at a close distance, e.g. 1m. If you read 90 cm or 1.10 on the lens while checking the focus with the LCD using magnifying your backfocus is pretty much off. You cannot check the backfocus with much longer focal lengths, e.g. your 50mm or 85mm.

My guess is that the camera crew missed the focus all the time, happens often with T1.4.

Hans

Edit: David was faster.

[Mitch Gross]

I think David is likely right on this. The image may technically be in focus, but wide open the resolving power of a SuperSpeed can drop considerably. It might not be that the focus distance was set improperly; it just might not be a particularly sharp focus. A simple test is to point at a finely detailed image (say a tree with lots of little branches or a sheet of newsprint) and shoot at both T1.3 and T2.8. Use the shutter to maintain proper exposure. Then compare the frames. Even for items that are in focus in each image, the T2.8 images should be noticeably sharper.

[Michael Epple]

Also, if your image is underexposed it becomes softer due to lack of signal.

[Yousuf Abbasi]

Excellent, thank you all for the help and advice. I guessed the speeds were soft wide open, but did not realize it could be this soft. I will do some tests at different f-stops and lightings to hone in on this.

[Milan Spasic]

Also, if your image is underexposed it becomes softer due to lack of signal.

+1

Low light and/or low contrast lighting combined with an ultra shallow DOF will definitely give you a soft appearance. :(

[Hans von Sonntag]

The image may technically be in focus, but wide open the resolving power of a SuperSpeed can drop considerably. Even for items that are in focus in each image, the T2.8 images should be noticeably sharper.

This sounds like SuperSpeeds are super soft lenses when wide open, looking like a missed focus. This is not the case. They have a distinct focus at T 1.4. At 2.8 they resolve more, though. I find for 1080p the resolution is fine wide open. Any test chart will show that. IMHO, the problem is the very shallow depth of field, the problem that focus pulling at T 1.4 with 50mm or 85 is a almost unsolvable task. Shallow DOF has its downsides.


Hans