HDR vs. Layer masks

[_ck]

I think I'm unclear as to the science of HDR, but how is HDR different to simply overlaying three layers - each containing a different exposure of one scene - and applying layer masks in such a way that different areas of the photo reveal varying combinations of each of these layers ? e.g. reveal more of the overexposed layer for shadowy areas and more of the underexposed area for the highly lit areas...

[Frank Lopes]

I think you essentially are right: if you were to superimpose the layers and pick and choose what part of each layer is visible, you would accomplish pretty much that same effect.

Using masks, however, you will need to be very precise or you end up with very strange halos and this is where the dedicated HDR solutions shine.

What most HDR packages do is take the luminosity of the different areas of the image as "masks" to make the appropriate adjustments.

Does that make sense?

Originally Posted by _ck

I think I'm unclear as to the science of HDR, but how is HDR different to simply overlaying three layers - each containing a different exposure of one scene - and applying layer masks in such a way that different areas of the photo reveal varying combinations of each of these layers ? e.g. reveal more of the overexposed layer for shadowy areas and more of the underexposed area for the highly lit areas...

[ktg222]

I am probably being heretical here, but 95% of the HDR/tone mapping work I see is not very good. The images look unrealistic or the image is so washed out because of the tone mapping software. That said, I have seen some very, very good HDR/TM images, but primarily exterior landscape photos. I did some experiments with an architectural photographer I work with and we could not replicate the results we got using manual masking with a popular HDR/TM product. Frank is right, if you manually mask the images you have to be very careful with the masking. I haven't totally given up on using HDR/TM software, but I think it will take a very specific workflow and massaging of the tone mapped image to surpass what I have been doing manually; at least for me and my client.

[TommyO]

_ck,

That is how we did it before HDR algorithms came about. A little more care and adjustment, but that was the basic premise. It's also how it was done with film.

[0lBaldy]

_ck, I will chime in and agree with all of the above.. just adding one little caveat... use all the tools at your disposal not just masking... When I HDR_tone map something I still combine with the originals and pick and choose different areas with masking and blending modes, color corrections, etc.. to get a good overall image.

It sounds like Ktg222 is doing precisely as you suggest.. when he says he is doing it manually he could also state he is doing Selective tone mapping

[Frank Lopes]

To avoid some of halo problems, I sometimes create black and white versions of the image and use them as masks on the layers.

This avoids most of the halos.

[Frank Lopes]

You are right.

No doubt that most of the HDR examples are so over the top that they lose all together what the technique was intended for: to increase the luminosity range of the image.

Instead people create these surreal, ultra saturated, cartoon like images that, even still have their own beauty, have very little to do with dynamic range.

Originally Posted by ktg222

...
but 95% of the HDR/tone mapping work I see is not very good
....

[palms]

Originally Posted by Frank Lopes

Instead people create these surreal, ultra saturated, cartoon like images that, even still have their own beauty, have very little to do with dynamic range.

Whoops, guilty, but in all fairness i don't know a awful lot about dynamic ranges etc. just what I like and don't

Palms

[MrRyan]

Originally Posted by ktg222

95% of the HDR/tone mapping work I see is not very good.

Agreed. In my workflow, I'll sometimes use HDR to add some punch to my photos, but not as a poster child for the technology. In my professional opinion, having a full range of exposure in the Darks, Mids, and Lights, looks horrible.

As for the original post. You are technically correct, that would make an image SIMILIAR to HDR, but it wouldn't be very good (in terms of HDR.) Shooting at the scene at different exposures, allows for WAAAY more detail, which is one of the main positives for HDR. A nicely balanced HDR image truly is beautiful, as the longer you look at it, (or play with it on the computer), you realize there is clean detail in ALL of the ranges.

[Hatsa]

Hi Guys!

Remember, HDR is future. These displays we're using now, cannot show HDR image as they really are. Check internet for HDR tech and you will understand.

[_ck]

Excellent comments everyone, thanks for the education.

[Volvo]

I think HDR is just another extension of creativety to Photography..Some results look good whilst others look awfull. Each has their own taste ey??..

[Mike Savad]

Originally Posted by _ck

I think I'm unclear as to the science of HDR, but how is HDR different to simply overlaying three layers - each containing a different exposure of one scene - and applying layer masks in such a way that different areas of the photo reveal varying combinations of each of these layers ? e.g. reveal more of the overexposed layer for shadowy areas and more of the underexposed area for the highly lit areas...

each looks different in the end. done in photomatix, tiny details, shadows, texture, color, are all enhanced. layer masks you have to do it by hand, and the effects are a bit more plain looking. sometimes though you have to do it that way, since photomatix tends to noisafy the image when you don't have enough shadow information.

i personally find i overdo the image when using masks.

---Mike Savad

[Alan_P]

HDR is very different than masking. The eye is very sensitive to edges and is not very sensitive to gradients. The HDR compression alogorithms will try to keep the edge relationship strong by adding gradients between the edges. This type of tone mapping can take two areas of equal brightness and render them as very unequal brightness. This is the key to HDR.

The algorithms are propriatary so the details are not known. There are often unwanted effects (i.e. HDR messes up skin color) that will need to be fixed in Photoshop.

There are sliders in the HDR software which are used to alter the compressed image. One of these is local contrast (structure). This brings out details and is often the one used to produce the "HDR effect". Some people use the HDR software on jpeg images. They are using local contrast to produce an artistic effect. A jpeg image is already tone mapped and the HDR software is not needed.

Multiple exposed images processed with then intent of producing realistic images do produce realistic results. Multiple and single images processed with HDR software with the intent of producing exagerated local contrast images for artistic purposes do that.


Alan