Build 17 with a 35mm Zeiss Ultra (12mm) @ 2k 16:9

[DeadPixel]

Hi

Yesterday I received a call from set with the following issue; when shooting on the RED set at 200 ASA build 17 at 2k at 100fps. Shooting for 16:9 on a 35mm format 12mm Zeiss Ultra Prime the shot was OUT OF FOCUS "soft" the shot was over a lake with strong back light.

As they were shooting 2K on a 35mm format lens, we all know that the lens focal length becomes larger... Yet there should not have been any Focus issues.

1) Could the cause of the focus shift been RED related due to going from 4K to 2K
2) Could it be due to... shooting excessive highlights (Back Light)
3) Could it be due to...Camera set to 200 ASA and not 320T default setting.

4) OR the fact that 35mm lenses are collimated to within a 1/1000" circle of confusion specification and 16mm lenses are collimated to within a 6/10 000"
When shooting at 2K with a 35mm Primes with its larger circular confusion as shot on this production, by design the focal plane (new focal plane) will not been as critical to cover this 2K format and would result in an out of focus shot.

The camera was brought back to HQ in the evening and we tried to replicate the same problem, shooting same frame rates and back lit the subject and everything seemed to be fine.

Has anyone else had similar problems / solutions ???

 

[J. Bernard Vallon]

collimation on shorter focal length lenses is incredibly critical, regardless of your format or sensor footprint. If they were measuring focus and not focusing by eye, its pretty easy for that shot to be soft. Temperature changes can mess up collimation, so even if it was sharp in the shop it could have shifted during transit.

Of course 2k is less sharp than 4k, they might be seeing the difference between the two formats. Does the softness look like out-of-focusness or debayer softness?

 

[David (dudi) Namir]

when shooting 2K at a wide angle lens use a 16mm format lens, never a 35mm format lens.
Wide angle lenses are less sharp than longer.
When you shoot 2 K you also loose some sharpness.
Summing up this two factors will result a out of focus image

 

[Greg M]

The 12mm UP at 2k does not make the focal length longer, you are simply shooting out of the center of the lens.

The problem is likely that your camera is slightly out of collimation, and you dont notice it at 4k, but it becomes very evident at 2K with a wide angle lens as you are now using the center of the lens and the center of the sensor .

Have your camera properly collimated and see if it makes a difference.

2K will never be as sharp as 4k though, I typically avoid 2k.

 

[Thomas Wright]

Hi


As they were shooting 2K on a 35mm format lens, we all know that the lens focal length becomes larger... Yet there should not have been any Focus issues.

The focal length always remains the same, the field of view changes.

~ what they said.

 

[Vico Martin]

Hi
1) Could the cause of the focus shift been RED related due to going from 4K to 2K
2) Could it be due to... shooting excessive highlights (Back Light)
3) Could it be due to...Camera set to 200 ASA and not 320T default setting.

4) OR the fact that 35mm lenses are collimated to within a 1/1000" circle of confusion specification and 16mm lenses are collimated to within a 6/10 000"

1) No, the sensor size and image circle is the same, the red only record the "window" of 2K
2) Soft focus for highlight? Never see.
3) No, RedOne records RAW, 200, 50, 800... it´s only metadata.
4) same as 1)

Sorry man, soft focus with a 12mm must be frustrating. If you can´t find explanation then kill the AC. :emote_hippie:

 

[Cail Young]

Even at infinity, wide angle lenses at 2K on RED look soft. It has to be REDCODE.