This Post is for Those Wondering if HDR is Worth the Effort

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TedG954

Senior Member
I have been reworking some old photos that I won't be able to take again. Here's an example of a shot that was really poor to begin with, and how the HDR process can make some improvements. HDR is definitely worth the effort.

View attachment 20126
 
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Dave_W

The Dude
I see you're calling your process "HDR" but is it really HDR in as much as you've taken 2 or more individual photos and combined them? Or are you doing an "HDR-like" processing so as to appear to be an HDR image?
 
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TedG954

Senior Member
Mojo Dave said:
I see you're calling your process "HDR" but is it really HDR in as much as you've taken 2 or more individual photos and combined them? Or are you doing an "HDR-like" processing so as to appear to be an HDR image?
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Well, Photomatix calls it "HDR", so you can make your point with them.
 
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Dave_W

The Dude
TedG954 said:
Well, Photomatix calls it "HDR", so you can make your point with them.
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I think that would be an easy argument to win. HDR is defined as a 32-bit image - see definition below -

Whether an image may be considered High or Low Dynamic Range depends on several factors. Most often, the distinction is made depending on the number of bits per color channel that the digitized image can hold. However, the number of bits itself may be a misleading indication of the real dynamic range that the image reproduces -- converting a Low Dynamic Range image to a higher bit depth does not change its dynamic range, of course.
·8-bit images (i.e. 24 bits per pixel for a color image) are considered Low Dynamic Range.
·16-bit images (i.e. 48 bits per pixel for a color image) resulting from RAW conversion are still considered Low Dynamic Range, even though the range of values they can encode is much higher than for 8-bit images (65536 versus 256). Converting a RAW file involves applying a tonal curve that compresses the dynamic range of the RAW data so that the converted image shows correctly on low dynamic range monitors. The need to adapt the output image file to the dynamic range of the display is the factor that dictates how much the dynamic range is compressed, not the output bit-depth. By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range.
·32-bit images (i.e. 96 bits per pixel for a color image) are considered High Dynamic Range. Unlike 8- and 16-bit images which can take a finite number of values, 32-bit images are coded using floating point numbers, which means the values they can take is unlimited. It is important to note, though, that storing an image in a 32-bit HDR format is a necessary condition for an HDR image but not a sufficient one. When an image comes from a single capture with a standard camera, it will remain a Low Dynamic Range image, regardless of the format used to store it.
 
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TedG954

Senior Member
Mojo Dave said:
I think that would be an easy argument to win. HDR is defined as a 32-bit image - see definition below -

Whether an image may be considered High or Low Dynamic Range depends on several factors. Most often, the distinction is made depending on the number of bits per color channel that the digitized image can hold. However, the number of bits itself may be a misleading indication of the real dynamic range that the image reproduces -- converting a Low Dynamic Range image to a higher bit depth does not change its dynamic range, of course.
·8-bit images (i.e. 24 bits per pixel for a color image) are considered Low Dynamic Range.
·16-bit images (i.e. 48 bits per pixel for a color image) resulting from RAW conversion are still considered Low Dynamic Range, even though the range of values they can encode is much higher than for 8-bit images (65536 versus 256). Converting a RAW file involves applying a tonal curve that compresses the dynamic range of the RAW data so that the converted image shows correctly on low dynamic range monitors. The need to adapt the output image file to the dynamic range of the display is the factor that dictates how much the dynamic range is compressed, not the output bit-depth. By using 16 instead of 8 bits, you will gain precision but you will not gain dynamic range.
·32-bit images (i.e. 96 bits per pixel for a color image) are considered High Dynamic Range. Unlike 8- and 16-bit images which can take a finite number of values, 32-bit images are coded using floating point numbers, which means the values they can take is unlimited. It is important to note, though, that storing an image in a 32-bit HDR format is a necessary condition for an HDR image but not a sufficient one. When an image comes from a single capture with a standard camera, it will remain a Low Dynamic Range image, regardless of the format used to store it.
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Well, I guess you win.

If you already knew the answer, what was your point in asking?

It was't really that important.
 
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Dave_W

The Dude
Definition continued - (from HDR images in photography - About Dynamic Range, Tone Mapping and HDR Imaging for Photography)



Can't I just create the exposures from one RAW file?
Not really. Your RAW file contains data captured by the sensors for only one exposure. The total dynamic range you can reconstruct from one photo converted with different exposure settings can never be more than the dynamic range captured by your camera, and this is rather limited (seeabove).

Converting the RAW file to images with different exposure levels is a bit like slicing the dynamic range of the RAW into several parts. Combining the parts back into an HDR image will at best re-produce the dynamic range of the initial RAW file

That said, if you are using a good RAW converter to derive fake exposures from a single RAW file, you will probably notice that the HDR image created from the fake exposures shows more dynamic range than the pseudo-HDR image obtained by converting the single RAW file directly. This is because your RAW converter includes a good noise reduction function, and this has an important effect on the dynamic range. You RAW converter may also include the ability to continue to retrieve highlights details when one or two of the color channels have already reached saturation

So, a good RAW converter includes functions designed to optimize the dynamic range retrieved from the raw sensor data, but this does not change the fact that the dynamic range of a RAW file is limited to one exposure only. Unless the dynamic range of your scene is low, you will need to take more than one exposure to create an HDR image of the scene.
 
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Dave_W

The Dude
TedG954 said:
Well, I guess you win.

If you already knew the answer, what was your point in asking?

It was't really that important.
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For one, I wasn't quite sure what it was you were calling "HDR", hence the reason I asked. But truth be told, I feel it's important that we not mislead the many people who come here to learn about photography. Maybe it's just me but I think it's important to those who don't know the difference that we call a spade a spade and a diamond a diamond. Not only that but your reply gave the distinct impression that you did not understand what an HDR image was so I felt it was important to at least follow up with a clear definition for those who really don't know the difference. But hey, if you want to call these HDR's, feel free. I'm not going to lose any sleep over it.
 
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TedG954

Senior Member
I'd like to offer my sincere apology to everyone on this site for misleading them as to the term HDR. I was just trying to offer some encouragement.

My original post was intending to show how you can bring life back in to a dull photo. As it turned out, I defrauded you all with the term "HDR". My only excuse is "HDR" is what the processing program, Photomatix, calls the process. I guess I should have researched further before trusting Photomatix. Maybe a class action lawsuit is in order.

While I never claimed to be an expert, I stand corrected. If anyone feels betrayed, has suffered physical injury, or financial loss, from my erroneous post, please send me a PM and our lawyers can work it out.
 
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Rick M

Senior Member
Nice work Ted! In Photomatix "light" (I have the cheap version), the single image process creates a "simulated" HDR image. I believe it's really just called tonemapping when you use one image. This works great for when you have one image like Ted had above. I use it where true HDR is not possible such as moving objects. I think the greatest confusion is when folks think that changing exposure values and merging them is going to make them true HDR and I believe Dave's explaination addresses that confusion very well.
 
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Rick M

Senior Member
If this is going to be a class action, I'd like to register for a piece of the pie! I'm still waiting for a few bucks from the Debeers diamond suit, maybe between the two of these, I can buy a cup of coffee :)
 
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madcapmagishion

Banned
cnyram said:
If this is going to be a class action, I'd like to register for a piece of the pie! I'm still waiting for a few bucks from the Debeers diamond suit, maybe between the two of these, I can buy a cup of coffee :)
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You'll be drinking Maxwell House Coffee, and the lawyers will be popping a few bottles of Dom Pérignon 2000!
 
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TedG954

Senior Member
MOJO DAVE........... Thank you very much.

I have spent the afternoon "discovering" 32 bit HDR processing. I have experienced the difference, and I now understand. Again, thank you.
 
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