ASA rating and meters

[David Mullen ASC]

I'm still not clear on this, but is a RAW image even viewable? Doesn't it have to be converted to RGB to be viewable?

If so, the question is whether a conversion to a flat 10-big LOG RGB image would make the exposure range being captured more obvious, for anyone who doesn't mind looking at a milky LOG image.

When Lucas put up the converted "RAW" image on his Scratch station during L.A.R.T., it always looked really dark for material shot at 320 ASA. So if that's what RAW is, would it be confusing to look at? Would you be tempted to overexpose if looking at a dark image like that? Or would a low-con LOG image make the extreme exposure ends more visible on the monitor?

 

[Kevin Halverson]

The "RAW" image is "viewable" but not representative of anything that would be of value, it has to be de-mosaiced in order to be useful. The other thing to consider is how to map the 12 bit linear output of the sensor/quantizer to a luminance range that is useful. I proposed a 'look' that would only be useful to help see the exposure extremes since the dynamic range of the imager is greater than either the LCD or EVF. I would never use this as the only tool for setting exposure or making lighting choices, rather, its just another one that would be useful to be able to cycle through. This isn't the best solution, its just one that should be easy to add once in camera looks are enabled. What I want is a few quickly accessible functions that would allow for in camera exposure decisions that take into account the downstream flexibility, but don't abuse it to the point of being overly optimistic.

I still would like the histogram to be assignable to just after the de-mosaic step and ignore all other in camera settings, particularly the "ASA" choice. This would prevent someone from making an exposure choice based upon anything other than what is actually being captured.

Personally, my wish list idea is the electronic spot meter that I proposed (assignable number of photosites and three numeric values corresponding to the primary colors). When I used to shoot large format color transparency (4"x5") I used a spot meter nearly exclusively and found it a great tool. Having one that I could fly around the image and get luminance values for all three color channels would be an ideal tool as far as I am concerned.

Would love to learn what others think about the usefulness of any of these proposed tools.

Kevin Halverson

 

[Steve Sherrick]

Kevin,

This is a huge help. Much kudos for doing the testing and to others for thinking these issues through. I truly believe that by the end of 2008, there will be a lot of finely tuned methods of shooting with this camera with a lot of the major issues worked out and improvements happeing continuously by the Red team. We are at the beginning and I think a lot of this is to be expected for a brand new camera design. Without a lot of you guys doing this testing, it would leave those without cameras at the moment in the dark. Thanks!

Steve

 

[red1225]

500T-320D w/85
100T-64D w/85

...and so on and so on.

We never had this problem with film and it is a very simple math. Meters work just fine.

Look...the only way to figure this out is by trial and error. Your meter should be used for levels only anyway.

TRUST YOUR EYE!!!

 

[Sanjin Jukic]

Could be a useful tip from DSLR experience>>>

QUOTE:

"When shooting in RAW mode under tricky lighting, sometimes it is useful to set a slight negative exposure compensation (0.3-0.5). This decreases the chance of clipped highlights, yet still allows one to increase the exposure afterwards. Alternatively, a positive exposure compensation can be used to improve the signal to noise ratio in situations where the highlights are far from clipping."

1. Clipped highlights

2. Signal to noise ratio



MORE>>>