HDR file formats. Which is best?

I haven't played around that much with HDR images, but on the few occasions that I have, I have always wondered which is the best format to save the 32bpc file in. With "best", I mean most cross-application compatible, file size, etc.

PS CS3 can save as PSD, Radiance HDR, PBM, OpenEXR and TIFF. The TIFF format is not Logluv TIFF, which makes me wonder what it is, since Logluv TIFF was apparently developed to store HDR images.

IIRC, Photomatix stores as Radiance HDR, which leads me to beleeve that maybe that is the safest format. It is also around 1/3 the size of the PSD version.

So what are the pros and cons on these formats?

KrisCarnmarker said:

I haven't played around that much with HDR images, but on the few occasions that I have, I have always wondered which is the best format to save the 32bpc file in. With "best", I mean most cross-application compatible, file size, etc.

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Best depends on application. The .HDR format spans a humongous (76 orders of magnitude) range of luminance levels, at the cost of accuracy (1% quantization steps, just adequate enough for visual perception). The .EXR format spans a more 'reasonable' (10.7 orders of magnitude) luminance range, and thus has more accurate (0.1%) quantization steps in that range.
This page describes the format differences in more detail.

Both formats are good for our type of pictorial rendering, and both are usually supported by HDRI aware applications. I don't think one will see any significant visual difference for normal pictorial use, but the .EXR format offers higher accuracy in case it's needed, and it offers lossless compression.

IIRC, Photomatix stores as Radiance HDR, which leads me to beleeve that maybe that is the safest format. It is also around 1/3 the size of the PSD version.

Click to expand...

Photomatix stores in both HDR or EXR formats, and Photoshop reads/writes both.

Bart

Thanks Bart. That was just the type of info I was looking for.