2 replies to this topic

[CheungyDiver]

HDR (high dynamic range) is well known in digital stills and HD DSLR. Some proprietary programs such as GingerHDR  even give you 'natural' looking footage after render. Well I have been reading up on ETTR or Expose To The Right for shooting in RAW files. Seems that this technique helps in bring out the details in tricky low light situations by slightly over exposing the raw not to the point of clipping the highlights. 

 

Here is a much more detailed and knowledgeable explanation from an expert in this area:-   http://schewephoto.com/ETTR/

 

 

Here are just a sample of the discussion in ML forum :  http://www.magiclant...g31285#msg31285

 

 

 

Just to highlight the pluses:

 

1. Seems to get better low noise in underexposed areas in recovery.

2. More detail is captured due to more information stored espcially in RAW. better signal to noise ratio.

 

3. This is important for UW shooters - Lower ISOs could be used In most cases ETTR allows to use lower and also we typically shoot 24fps so shutter speed is slow at 48th sec.

4. ETTR in RAW mode is more accurate and the implementation of histograms in jpeg

 

 

I believe there is merit in finding out more on this technique for UW footage since we encounter some very tricky lighting situations near surface or shallow depth and also lost of warm colours as one dives deeper. Recovery using ETTR by using the histogram to expose just before highlight clipping seems to work well with stills. I also read in ML crowd that this technique could be applied to raw video footage and has this feature in ML firmware. Wonder if anyone has experienced with this?

 

 

 

Cheers

David

Edited by CheungyDiver, 13 June 2013 - 06:38 PM.

[Drew]

Exposure really depends on the DR of the sensor of the camera.  As you know, the Epic goes for resolution over DR and color, unlike the Alexa, especially in the wheelhouse range of (manufacturer declared) base ISO.   I've found the BMCC does well with ETTR because the sensor is pretty noisy in the shadows but handles highlights well in post.  In DSLR world, working with the D800 and 5D3 in the ISO100-800 range, the D800 has the DR that avoids the shadow noise of the 5D3 (even if the 5D3 can do RAW, it's still has noisy shadows as part of the sensor design).

ETTR may work to eliminate dark noise with center cameras like the Red, 5D3.  The Sony F55/Arri Alexa seem to have the DR to not have to do too much ETTR.  Underwater,  with the limited light, the ISO will have to be pushed but that comes at the expense of noise and decreasing DR (and resolution with the 5D3).

 

Another advantage of GingerHDR is that it processes .RAW files without transcoding. Which is a godsend IF you have CS6 AE or PP.  There are still a few bugs but it does work well.  Does well with CUDA acceleration.

[Ferg42]

I did find that I underexposed a fair bit to start with shooting raw with the mkiii. Then when I processed the shadows had excessive noise. I've been having a look at the ML 'Auto' ETTR (it's not really particularly 'auto'). It seems a bit convoluted, what with shooting a still, having a look, doing another one etc etc. I feel as though with a bit of practice I might be able to get it right quicker just by judging from the ml waveform or the canon histogram. But I'll try a few different methods underwater and see what gives best results.