Dragon focus Issue?

[David Battistella]

If it is a back focus issue the markings should not be spot on (assuming they are all shimmed and tested on a projector and then the back focus is set on each camera) I use my REDfocus now for all of this kind of thing. This way I know that the target to the focus plane is spot on. If anything is out then it's a lens thing.

But you guys are correct, get the widest lens on there, set a known distance and set the lens to that distance from the chart (I used 3 meters or six feet before I had the RED focus), get a large monitor, get in 1:1 zoom mode on the camera and set that focus as close as you can get it on the chart in the center of the frame. Then all the lenses should fall in line and be spot on at that distance.

This is for primes. with zooms you have to see how they hold the range.

Battistella

 

[Blair S. Paulsen]

The one thing I'm having trouble attributing to back focus error alone is the differences in focus results between 5K and 6K frame sizes when the sensor (Dragon) and the lens (UP wides from multiple sets) are the same. I suppose that the depth of field decreases as the the image circle increases so a slight error might reveal at 6K that is below the circle of confusion at 5K but I'm dubious that alone would account for it. I still have to wonder if a lens designed for S35 might exhibit some unaccounted for issues with stray light, internal reflections, the edges of elements, etc when trying to properly cover the larger aperture.

Cheers - #19

 

[Phil Holland]

Heh. This is one of those things where we need a bit more info.

Also, I imagine if one of us was on set it would be sniffed out in about 3 minutes.

 

[Gunleik Groven]

we are too expensive....

 

[Harcharan Singh]

Focus

Focus

Hi guys,
We had the Dragon but didnt have any
Ultra Primes to test today.All lenses were out
with Epics...
So give me day or two and I will come with
R3Ds
Thanks
Harcharan

 

[Andre W.]

With back focus issues, longer lenses take much more drastic movements to see a shift. Thats why usually if doing a back focus calibration with a lens on a body, you do it with the widest you have. 14, 16, 18mm are usually good ones to check it with. A very minor back focus adjustment can move you focus with these WIDE lenses DRASTICLY, where as that same minor adjustment will not have effected your 85 or longer lens.

So if you feel that your 16 is spot on, I would use that lens to set your back focus on the camera. Chances are it's a very minor adjustment that needs to be done, and you will notice that the rest of your lenses should still fall in line, with your longer lenses perhaps popping a little better.

 

[Michal M.]

Hi,
it is possible to know the distance between both positions of chip when you correct back focus issue?
Thanks

 

[Darin Limvere]

Pieced together a Dragon DSMC2 and was having similar issues. Then I noticed that 6k was quite a bit softer than 5k. Found this thread thinking in the back of my mind it was the back focus and did the adjustments. 6k is now sharper than 5k like it should be. Red has a youtube video and documentation for those who haven't done it before.