HDR and tonemapping of images

[dnmilikan]

This is a topic that may be of benefit to those who want to optimize their images under difficult lighting conditions.

Digital cameras suffer from the same malady as traditional transparency films in that they have an abbreviated tonal density range. This can lead to either underexposed shadows or overexposed highlights. In the case of overexposed highlights clipping can occur and if so the detail is lost.

One solution to this situation is to make three exposures of the same subject/scene. One two or three stops overexposed (to capture the shadow detail), one exposure as the camera suggests, and one exposure two or three stops underexposed (to capture the highlight detail). These compensations must be made with the shutter speed since aperture changes will alter depth of field. Additionally the camera must be mounted on a tripod and there must be no movement in the subject matter.

These three exposures are then combined. This leads to a single image with an extensive density range beyond what the available viewing devices are capable of depicting. This is compensated for by tonemapping the single image to an acceptable density range for presentation.

HDR is available in PS CS2 and CS3. Additionally third party software is available for this process. (Photomatix being one of these suppliers).

As I mentioned at the outset, this is not something for every image but it can save the day in certain instances.

[trulytango Profile Private message]

Hi there

HDR images are very interesting... has anyone got some for us to see? I remember someone posting a show a while back but I can no longer find the link.

Here's a link to some more info re HDR:
http://www.photoanswers.co.uk/Advice/Se ... g/?id=1388

Plus, learn more about Photomatix here:
http://www.hdrsoft.com/

Regards
Iris
UK

[BarbaraC Profile Private messageWebsite]

This is a technique I recently used in only a partial way when photographing a lit candle against a black background. First, I exposed for the flame, adjusting the speed and leaving the aperture to stand pat. Then I reset the speed to capture just the candlestick. Here's where I could have used a bit more knowledge of the HDR technique because, after choosing the two best images, I had to place the flame on a separate layer in Photoshop and then carefully erase down to it until it appeared to be the "real" flame.

Thanks to both of you, I'll be trying a slightly altered technique the next time I encounter one of those extreme situations.

Barbara

[dnmilikan]

http://www.cambridgeincolour.com/cambridge-gallery.htm

[trulytango Profile Private message]

Wow!

dnmilikan/Don? Absolutely stunning images... beautiful. Nice site too, very informative.

Thanks for the link.

Iris

[Davesconnect]

I am planning to master this. Have always been frustrated with the lack of dynamic range of digital.

Have recently taken possession of a Nikon D300, so will try bracketing exposures.

Dave

[BarbaraC Profile Private messageWebsite]

Dave, I fooled around with it today in CS3, and Photoshop tut-tutted at me for not using RAW images, which I could have done but I was too lazy to bring up the originals. That said, I can see how it would work extremely well, the only requirement being that both pictures be identical except for exposure. I do a huge amount of photography in my little basement studio, and I happen to love low-light work, but I've had big problems with mid-range detail. I'm going to play more, a whole lot more, with HDR.

Barbara

[gpsmikey Profile Private message]

For more entertainment/enlightenment on the HDR issue, there are a couple of other
threads from a while back on the issue (eep was also working with it). Here is one
of those other threads with some additional information ...

http://www.proshowenthusiasts.com/viewtopic.php?p=44551

mikey

[XaiLo]

These were all from a single image +-2stops images created in photoshop ran through photo matrix, ACR, and final tweaking in photoshop.

[trulytango Profile Private message]

Hi Xailo

Great shots... wonderful colours. The technique has resulted in superb digital art. Thanks for posting, it's been interesting to see such a range of images through this thread.

Regards
Iris
UK

[BarbaraC Profile Private messageWebsite]

Xailo, what filters did you use on these images? The effects remind me of some of the things I get from ColorEfex.

Barbara

[bigsewed Profile Private message]

Barbara
Remember with CS3 you can open a jpeg in Camera raw...
By placing as a smart object from camera raw and using masks you can come close to HDR results...
Wes

[BarbaraC Profile Private messageWebsite]

Only problem with that, Wes, is that I never shoot JPEG's. Everything's in the RAW.

Barbara

[XaiLo]

trulytango, thank you very much I'm glad you enjoyed the images.

BarbaraC, I did those pictures about six moths ago I don't do much HDR I was just doing some experimenting back then for a future project. The only filter I used was guassian blur, the HDR program I used was Photomatrix which accomplished the tonal processing after that I brought it back into Adobe Camera Raw and then back into photoshop for final tweaking. I did not like the results from Adobe HDR at all. And while the preffered method is to use bracketed images I found that a single image could yield decent results but you have to create your own under and over exposed images I created an action to speed up the process. a lot of it is subjective.

[BarbaraC Profile Private messageWebsite]

you have to create your own under and over exposed images

That's exactly how I did my own testing, but I have to go back and try a second time with two RAW images recently shot, one for the highs and one for the lows. If I can't get what I want using just Adobe, I'll look at the other programs because this is a constant problem due to my photographic style.

Barbara