exposure blending vs. HDR

Hi, my question is not camera related per se but I use the GX10 so do belong to this forum

What exactly is the difference between exposure blending and HDR?

I've seen images that use both techniques. I thought that HDR was a combination of images that produced a very wide dynamic range that is then tonally compressed to a) fit into a PC monitor (and printer) colour display range and b) mimic the impression of the range of light to dark in an image that we see in real life situations.

So what is exposure blending and how does it differ from HDR?

Many thanks.
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jamesza

i use Photomatix to blend "highlight & shadow" sometimes. not for any particular effect, but when it is not possible to capture everything within the DR of the camera. this procedure uses two images.

i don't use Photomatix for HDR.
i think HDR is blending + tone mapping.

i don't know what tone mapping is.
i guess i shouldn't do it if i don't know what it is... :^P

anyway, interested to see what you hear (ha).
i have read some about it, but it didn't sink in well.

long story short

both JPEG and RAW files record limited amount of light dynamics - because of that some portions of image can be clipped to white or black

let's say you made 3 photos: 0EV (clipped), +2EV (to record unclipped shadows) and -2EV (to record unclipped lights), none of this photos is perfect however...

the simplest exposure blending is when you select "clipped to white" (ie. sky or light source) region in 0EV photo and replace it with -2EV one, and "clipped to black" (ie. some deep shadow) and replace it with +2EV version

now you have one photo with no clipping at all but - depending on algorithm you used to chose/select which replace with witch effect can vary (from very good to unacceptable)

HDR is when you make - out of those 3 pictures - one, which contains all the info all 3 pictures have, so (ideally) there is no clipping at all... there is one thing however - you can't display/print that picture easily, because now you got 32-bits per channel (instead of 8-bits like in JPEG or 12-bits like in RAW)

so you apply so called tone mapping when some algorithm is trying to squeeze 32-bit light dynamics into 8-bits, so you can get normal JPEG/TIFF file (for displaying or for printing), also tone mapping allows for those "fancy" hdr effects (like tweaking global/local contrast, and not only simple levels)

the last thing is "pseudo hdr" when you apply some sort of tone mapping (non-linear filtering) to one exposure - you don't get anything more (clipped is still clipped) but resulting photo "looks like hdr"

all in all exposure blending is easier/faster, however effect may be different for different photos, while hdr is state of the art technique, however it is somehow time consuming (at least when you are learning it)

also, depending on source, someone can use "hdr" to name 32-bit per channel image (which is ready for tone mapping) or to name tone mapping process itself

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Cuiusvis hominis est errare, nullius nisi insipientis in errore perseverare.