HDR Questions

[VortexOne]

I'm sorta new to photography, and understand quite a bit about its different aspects, but there's one thing I find confusing. HDR. I've read about what it is, but I don't get how it works or why its important or good. I get that its basically taking 3 pictures, one regular, one underexposed, one overexposed, and combining them, but my big question is, what is the point of this? Can anyone help me?

 

[naaaach]

HDR = High Dynamic Range, and it is exactly that. It is used to produce an image with combined exposures. For example, you're taking a photo indoors, and there is a window in your frame. You can meter your camera with indoor lighting, which means the light from the window will be overexposed. Or, you could meter your camera with the light coming from your window. But then, your subject indoors will be underexposed.

HDR takes the different exposures and combine them in one photo, so in the above example, the final product will be a correctly lit indoors subject, and a normally exposed window. Best of both worlds.

It can add a very dramatic effect to some shots also, if done right. If done right.

 

[VortexOne]

Thank you very much. That fixes my confusion.

 

[ann]

and it is not always 3 exposures. It will depend on the contrast range of the image in question.

 

[VortexOne]

Really? Then someone needs to change the Wikipedia article. Thanks!

 

[naaaach]

and it is not always 3 exposures. It will depend on the contrast range of the image in question.

Yeah, I've seen HDR photos that combine 10+ images.

 

[ann]

the rule of thumb is at least three,

I have several images that have more than 13 exposures. Wikipedia is not always correct.

 

[KmH]

Less than 3 exposures is a psuedo-HDR.

As mentioned, the number of exposures needed to make an HDR of a particular scene is determined by the total dynamic range in the scene, so it is a variable number.

Many new to making quality HDRs don't appreciate the amount of work that is involved in doing the necessary image editing.

The exposures are initially combined, software like Photomatix Pro is good, and then the image is tweeked using Photoshop and Photomatix until it is done.

There are a lot of poorly done HDR's out there.

 

[naaaach]

There are a lot of poorly done HDR's out there.

Yeap. Just to give you an idea, bad HDR, better-than-the-first HDR.

 

[KmH]

In all honesty #2 was made with an insufficient number of exposures, the exposures that were done had the wrong EV range, and is neither a great, or even good HDR.

The mountain on the left is far to dense (dark, little detail) and the building on the right is still underexposed.

Are both of those your photos?

 

[naaaach]

In all honesty #2 was made with an insufficient number of exposures, the exposures that were done had the wrong EV range, and is neither a great, or even good HDR.

The mountain on the left is far to dense (dark, little detail) and the building on the right is still underexposed.

Are both of those your photos?

Ah, true, I guess. I just quickly google'd and picked out some, and thought that looked decent. Well, at least compared to the first one. Neither of them are mine. Perhaps this one shows the multiple exposures combination a bit better?

Then again, I am in no way an HDR expert.

 

[lyonsroar]

^You really shouldn't be posting others photo's. It violates copyright law...

 

[naaaach]

^You really shouldn't be posting others photo's. It violates copyright law...

Got it, linked instead.

 

[ann]

here is one that is 8 exposures

http://www.thephotoforum.com/forum/hdr-discussions/229341-first-class-suite.html

used PS, Photomatix and Topaz labs to process

 

[clanthar]

To really understand HDR you need think about it from the other end -- the print.

Assuming the final goal is still a photographic print or at least a display that has been calibrated to print proofing standards, you have a dynamic range in your target that is fixed. White paper can't get whiter and the black inks we use to make prints aren't going to get blacker. Therefore the maximum dynamic range of the output media is fixed -- say it's X. (In fact it's between 4 and 5 stops).

Take a low contrast scene outdoors on an overcast day and you may have around 5 stops of dynamic range. Easy fit to the print.

In bright full sun that dynamic range is going up. We expect photos that we take on sunny days to include black shadows below the detail threshold. You may have 9 real stops in the scene now but that print paper isn't going to expand it's range to match. If you're recording X + 100% how are you going to squeeze it all into X?

Now the sunlight shifts to the side and the dynamic range goes up another 4 - 5 stops. You're looking at X + 200% or more. Even your camera sensor can't capture it all. Standing there in front of 14 stops of dynamic range you get the bright idea to do a 5 exposure HDR capture. Eureka! You've got it all. Photoshop will combine those 5 exposures into a 32 bit HDR image for you. That's four billion two hundred and ninety four million nine hundred and sixty seven thousand two hundred and ninety six shades of tone -- YES!

Now it's time to print your HDR masterpiece. You need an 8 bit image to take it out to print. We don't have and we're not going to get 32 bit print capability. We settled on 8 bit to print long ago because the dynamic range of the print is a fixed target and it's staying that way. 8 bit is two hundred and fifty six shades of tone going out to a print which works very well. All you've got to do now is figure out which four billion two hundred and ninety four million nine hundred and sixty seven thousand and forty shades of tone you want to dump. This is why there are so many bad HDR photos out there. The photographers have a hard time finding the right 256 tones to keep.

Joe