What is HDR?

[PHeller]

And how does one use it?

[tcadwall]

High Dynamic Range.

This is a technique that expands the dynamic range that your camera sensor is limited to. Multiple shots at different exposure (typically all settings equal except shutterspeed) are blended together in post. This will bring out the blues in the sky, at the same time that it will give you details in shadows.

Here is a thread with some samples, and discussion.

http://www.dcresource.com/forums/showthread.php?t=29062

[Prospero]

Here is a long thread about HDR with several examples. http://www.dcresource.com/forums/showthread.php?t=29062

Basically, HDR stands for High Dynamic Range Photography. Your camera can capture a limited dynamic range. Many scenes, however, have a dynamic range that is larger than that.

The trouble with that is that it is impossible to capture some scenes without either having very dark shadows or clipped highlights. HDR can solve this problem. In this technique you blend several different exposures of the same scene, mostly an severly underexposed and a overexposed picture and several in between. The result is a 32-bit image, which then has to be tone mapped, to be able to convert it back to a regular 8-bit image.

Both the blending and tonemapping can be done with photoshop CS2 or programs like Photomatix. I use Photomatix myself, in my opinion the easiest way to create HDRs.

Here is an example, more can be found in the thread I linked to.

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EDIT: Tcadwall types a lot faster than me :D

[PHeller]

How do I use a single JPEG to do it?

I try, but it says "Dynamic Range not large enough"

Do I have to change exposure then save as RAW?

In Photomatix I can get it to work...but images are all messed up.

[Prospero]

To create an HDR with one JPEG, you will have to create two, but preferably more, versions of the JPEG, each edited to look like it has been exposed differently. You can then load these to Photomatix and create a HDR like usual.

However, you will gain very little. This strategy is a very elaborate way of applying the shadow-hightlight tool and using the unsharp mask to raise local contrast. The thing is, you cannot increase the dynamic range of a JPEG file. There is no way you can recover detail in blown out highlights and blacked out shadows. These things are what HDR is all about.

A raw file has a higher dynamic range than a JPEG, so you will have a bit more range to work with. Photomatix can import and tonemap Raw files. In cases where the extra range of the Raw is all the extra range you need, you can create HDRs like that.

If you import Raw files to Photomatix the colours are indeed messed up. You can correct that with auto colour and auto levels in photoshop or use the colour balance tool.

[tcadwall]

The idea of trying to use one photo (raw OR jpg) to achieve HDR is a bit of a waste of time IMO. Really, you can tweak a single raw file to "tone map" it to a jpg simply by using a raw editor. That is essentially the same thing but removing quite a few steps of work.

Remember the reason to use HDR is to gather more stops of light than what the sensor is capable of doing at a given exposure. IOW - a perfect exposure on a Digital sensor will still not represent as much dynamic range as what is really in many scenes. THIS is why you would use HDR techniques to take multiple images and be able to map the shadows and highlights in a way that you have better overall depth.

[Rooz]

HDR f'ing sucks if you ask me.
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cos i can't do it. :D

[PHeller]

I've been experimenting alot, and can't seem to get my pictures clear.

I think I may be having some focusing issues with the lense and maybe also the fact that I'm touching the camera when I take longer exposures, which is throwing off the focus.

Do most of you take HDR pictures using a tripod and a remote release or what?

[tcadwall]

I know that some people do this hand-held. Your best bet would be to use your tripod, and a release. If you don't already have one, the ML-L3 is a great low-cost solution for most Nikon DSLRs... Since it is IR, it is a very convenient release to have, and it is only like $17. Don't recall which model camera you have.

It is also a good idea to use whatever bracketing your camera provides. That way you don't have to touch the camera as often

[PHeller]

How can people do this hand held? I thought the pictures had to line up perfectly?

[tcadwall]

The pictures MUST be aligned perfectly - of course. But this *CAN* be done in post.

[Prospero]

It is indeed best to use a tripod and remote for HDR, in that way Photomatix can usually allign the images sufficiently.

I hardly ever shoot HDRs with a tripod, for two reasons. Mainly because I am to lazy to carry a tripod around, but also because sometimes I shoot from a place where there is not even enough space to set-up a tripod.

When I shoot wide-angel images, however, Photomatix can hardly ever get the images alligned. This is because when the angle changes with such a lens, the perspective changes a lot. Photomatix cannot handle perspective when alligning.

Therefore I use PTGUI. This software is made for alligning images when making panoramas. This is a very powerfull stitcher and it can handle perspective very well. Using this software the images can be alligned on top of each other and each image can be exported seperatly.

The exported images can then be imported to Photomatix and the HDR can be created as usual. When creating the HDR now, the alliging images option must be off, because Photomatix can mess up the alliging again when it tries to allign the wrong edges.

One disadvantage of this method is that the stitching with PTGUI does induce some type of barrel distortion. This can be fixed in Photoshop, though.

Anyway, I hope I have made things a bit clearer. Somewhere next week I'll write a more detailed HDR tutorial, with pictures to illustrate the various steps. That might make things more clear.

[tcadwall]

Prospero Rocks! Great mini-tutorial!:D You are definitely in the clique.:eek:

[Stoller]

Here is a nice article I found. PDF format, HDR ROCK'S!

http://www.guyjbrown.com/articles/hdr-nov06.pdf

[Prospero]

Prospero Rocks! Great mini-tutorial!:D You are definitely in the clique.:eek:

LOL :D of course I am in the clique, I was one of the co-founders :D

Just wait until I post my large tutorial, after that I will be the clique leader for sure :D :eek:

Nice article, Stoller. Thanks for posting the link.

[Stoller]

Nice article, Stoller. Thanks for posting the link.


Interesting the author states HDR could become the norm...

I would hope not. I like it for a photography option, but not for every picture. :rolleyes:

[Prospero]

Interesting the author states HDR could become the norm...

I would hope not. I like it for a photography option, but not for every picture. :rolleyes:

I agree, HDR is a nice effect, but if there is nothing else, the effect starts to get boring.

That said, there is a difference between HDR and a tonemapped HDR. If a camera can capture images as a 32bit HDR images it does not mean that it will be tone-mapped. It will only mean that even in the pixels that seem white, there is still detail captured. Thus, the HDR will look just like a conventional image, unless it is tone mapped.

[jcon]

LOL :D of course I am in the clique, I was one of the co-founders :D

Just wait until I post my large tutorial, after that I will be the clique leader for sure :D :eek:


:eek: I knew it! You best let me in, dammit! LOL:p ;)

[Prospero]

:eek: I knew it! You best let me in, dammit! LOL:p ;)

I thought you were the other co-founder :D

The clique is so secret we don't even know who the other members are anymore :rolleyes:

[jcon]

I thought you were the other co-founder :D

The clique is so secret we don't even know who the other members are anymore :rolleyes:

LOL, I must have misplaced my founders badge:eek:


It's nice to get some laughs here again!:D

[PHeller]

My problem is this:

If I can hold the camera steady enough to take a bracketed shot during the day, are the results (EV steps) going to be big enough to get a dramatic HDR image?

When I tried taking pictures during the day, the EV steps were so minimally noticed (even set on -2.0 step) that my pictures were practically the same!

I shall try again.

[Prospero]

I had the same problem with bracketing, most of the time the shots did not seem 2 stops apart. Now I bracket manually. Works fine most of the time (when I use the panorama software to allign). Bracketing would be better, though, because in cases of cloud movement my shots are to far apart on windy days.

Anyway, I usually take 8 shots for HDRs, which means that I would have to bracket more than once anyway (which limits the benifits from bracketing).

[herc182]

I always use the bracket feature (3 frames) and generally set them 1 stop apart. I generally have the D80 set at -0.5 stop because it tends to overexpose photos.

The shots are always hand held.

Most of the photos here (in fact 98% of them!!) are with HDR:

http://www.flickr.com/photos/philipduarte/

HDR is a useful tool (which i have experimented with a lot) but i sometimes think it is not true photography. I dont know why. I am a firm believer in NOT using PP but obviously you have to with HDR. However, i see HDR as a cheap mans cokin filter :-) It is very very useful in tricky lighting situations.

These are good extensive guides to HDR too:

http://www.cambridgeincolour.com/tutorials/high-dynamic-range.htm

http://www.naturescapes.net/072006/rh0706_1.htm

[PHeller]

I found the problem! I never was checking the "Attempt to Align Source Images" box in Photoshop!

Once I did that the images came out much better!