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Possible Duplicate:
Should I convert RAW to jpeg before making an HDR?

I just recently started shooting HDR images, and I like the effect when it's done right. I was just wondering, when I take 5 bracketed images and tonemap them using Photomatix Pro, is it better for me to just give the program the 5 RAW images, or should I convert them all to JPEG before tonemapping? Sometimes it seems like the tonemapping process adds a lot of noise that wasn't previously there, and I didn't know if perhaps using RAW images caused that. If you want to see the HDR images, feel free to view my G+ profile. Thanks!

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marked as duplicate by Itai, rfusca, John Cavan, mattdm, Rowland Shaw Aug 2 '11 at 17:47

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Firstly you can produce HDR images with either raw or JPEG. However as raw files contain greater dynamic range than JPEGs to begin with it makes sense to shoot raw if you plan to produce HDR images, as you'll get better results.

To expand on your point about noise here is an important relationship between dynamic range and noise. Simply put dynamic range of a camera is the ratio between the brightest and darkest things the sensor can capture. The limit on how bright an object you can capture with digital is simple - it's the point at which the sensor pixels become saturated (full) after which an extra light does not affect the signal.

The limit on how dark an object you can capture is more complicated. You ought to be able to go darker and darker until there are no longer any photons being reflected from your object into the camera. However, there is a base level of noise you get even when the camera is not exposed to light. As you photograph darker and darker objects there will then come a point where all detail in the object is lost to noise.

The dynamic range is thus determined by noise, but more importantly noise and DR are inverses of each other! The noisier the camera the lower the dynamic range and vice versa.

What's happening when you're tonemapping is that the software (which has the job of taking a true high dynamic range image and squashing that down into a standard dynamic range image suitable for display on regular screens) is pushing the captures too far in order to even out brightness variations and you're seeing a lot of noise. The solution to this is to extend the dynamic range of the data you're working with, as we've established this will lead to less noise. The way to do that is to increase the range of camera exposures by capturing more images, or moving your 5 bracketed images further apart.

The fact has other consequences too. Your HDR image doesn't have to have the mega contrasty painting look that many people object to, it's possible to use HDR techniques to produce an ordinary looking image, but with exceptionally low noise!

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So using raw images for the tonemapping shouldn't affect the quality at all, except to possibly make it better quality? –  benmanbs Aug 2 '11 at 15:46
    
Yes, using raw gives you more data to work with, so it wont make things any worse (considering you can produce JPEGs equivalent to the ones the camera produces, from the raw on your pc) but ought to improve the quality. –  Matt Grum Aug 2 '11 at 15:55

Being a canon user, I find using DPP to remove the noise and any chroma etc first, then TIFing the images so they don't lose any detail/quality and throwing those into the HDR program of choice (not sure if photomatix will take tif?). Using a RAW as is will have plenty of noise unless the HDR program you have has good noise reduction.

This is slightly more longwinded than throwing the pics into the HDR program, and takes up a lot more room with the TIF files. It should give you much better quality outcomes though, and if your RAW converter of choice saves your changes, then you can delete the TIFs after to free up the space and just export them if you need them again.

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I use Nikon, what is DPP? –  benmanbs Aug 2 '11 at 14:23
    
DPP is the Canon software that comes with. In many peoples opinions is the best RAW converter for Canon RAWs, colour and qualitywise. I don't know how any Nikon software compares –  Dreamager Aug 2 '11 at 14:34

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