Using SX20IS to create HDR

[bjlasota]

I was wondering if anyone had a quick tutorial on creating different exposures quickly for creating photos through HDR. I have PSPX3 which I realize isn't the best program to use, but for now, it'll have to work. I'm wondering what's the quickest way to change exposures using the SX20IS. The camera will be on a tripod so I don't have to worry about movement, but I am worried about time between each shot for city views and such. Also, do I have to manually compose the shot or can I put the camera in Tv or other auto modes?

[Jon]

Use AEB (p. 91) for up to 2 stops each way from the "normal" exposure. Whether to use Tv, Av or another option depends on what you're shooting, among other things. If you let the aperture vary, you might (although this is less likely with a PowerShot) see DoF issues, where lighter objects (taken at a smaller aperture) out of the plane of focus will be crisper than dark objects at the same distance. Or if you're shooting something where objects in the picture are moving, different shutter speeds might mean that dark objects show more motion blur than light ones due to exposures 4x as long.

[exwintech]

Bjlasota - Like the SX10, the SX20 will set for multi-images for HDR. While the AEB in the camera will give you 3 images at up to -2EV / +2EV, it can do better.

Some DSLRs will do 5 or more images in AEB mode. This gives a wider spread of Dynamic Range variation and detail, which is beneficial for doing HDR.

The SX10/SX20s can't do that on AEB, but as you have a tripod, you can do it very easily, manually.

As Jon says above - don't let the aperture vary - lock the aperture in, and use Exposure Compensation.

Start by ensuring that the tripod is set up very firmly. Mount the camera and after pre-composing the shot, using Aperture Priority, tighten or lock the tripod adjusters. Use ISO-80 unless light conditions force otherwise.

Set the Timer - you have 2-second, 10-second, and Custom. As you are going to - very gently - touch the camera between shots, so might cause very small "vibes" in the tripod - make a Custom Timer setting of 5-seconds to allow those to settle.

I'll assume that you're doing a scene, at the Wide end of the Zoom, and the Aperture is at f/2.8. Press the -/+ so the Exposure Compensation bar shows onscreen - you can shoot while it is displaying.

From now on the only things you touch are the Shutter button, and the rotating ring around the 4-way-pad to change Exposure. Make sure that you don't kick or bump the tripod during the whole sequence.

Set Exposure Comp to -2EV, then gently press the Shutter button to Focus-and-Beep, then as gently, full-down, and get hands clear of the camera. After the camera has that image, very gently rotate the ring to -1EV, and repeat the procedure with Shutter-Timer-Shoot.

Then continue the sequence for 0EV, +1EV, and +2EV, to complete your 5-shot sequence.

That assumes that you want your HDR set of images "centred" on "0EV". You can go above or below 0EV centred - but will have to reduce steps to 2/3EV, etc, to keep the steps even. Or work from 0EV and have 5 images at 2/3EV or 1/3EV steps. As you'll see - that would let you do, say 7 images, if you wanted to try that.

If you start at 5 images from -2EV to +2EV, you'll very quickly see how you might want to adjust the 'width' of steps, so on.

As we haven't used a DSLR that can zap 5/7/9 images AEB in under a second - however careful we've been not to 'vibe' the camera and tripod - there can be very slight positional differences between the images. So use an HDR program that starts by "Aligning" the images after importing them.

One of the standard HDR programs in Linux - most Distros have it in Repository - is 'qtpfsgui' - it's one of two I've tried, though I'm not a frequent HDR-user, and works well.

There's a (free) Windows version (also for Mac) - called 'Luminance' - which does have a very functional "Align after Import" setup. Then a lot of "very interesting" operations and options for image adjustment and enhancement.

A friend here (the lady with the SX20 I've mentioned before) - is using the SX20 and Luminance combo (in XP-Pro SP3) - with what she finds to be good results.

Dave.

[nexus411]

good info exwin, i'm gonna try luminance

[MingFromMongo]

Sorry guys, but I'm having a "stuck on stupid" moment or ten thousand today. I am attempting to use the AEB feature on my sx20 but I must be missing something in the manual. Do I have to do three separate shots like exwintech explains in the above post (although he discusses five) or is it supposed to be a continuos shoot? It seems that no matter what I try using how I interpret the instructions, I take the exact picture exposures three times. Please, can someone explain this so as to penetrate this extra thick craniumof mine.

[Jon]

You holding the shutter button down for it to take 3 shots? Have you set the exposure shift interval? Flash turned off, and Continuous shooting off?

[MingFromMongo]

Thanks for the reply Jon.
No matter what I try it doesn't shoot three shots. I've held the shutter for three minutes and omly a single shot was taken. Exposure shift was set to -2, 0, +, And the flash is down. Continuos shooting occurs when I put it in that mode. I've tried the AEB with and without continuos on regular and AF and the exposures are the same. With continuos off there is still just a single shot taken when set to AEB. Am I mistaken in my interpretation of the manual?

[denncald]

It only requires a single press of the shutter button, do not hold it down. You should be using a tripod to keep the camera steady while it takes the three shots. Set up AEB per instructions on pages 91 and 92, then when you take the shot(s) you should half-press the shutter to let the camera focus and set your standard exposure setting (+/- 0 setting). The camera will take the first shot at the standard, then two more at whatever you set for the + and - values.

You should also make sure your EV setting is set to zero, not a + or - value. Also, set your mode to Av so the aperture is fixed. The camera will then only vary the shutter speed.

Recent versions of Photoshop Elements (I use version 10) will also allow you to create an HDR or Exposure Blend from the three images. Here's a link to some free HDR software;

http://www.techsupportalert.com/best...r-software.htm

I prefer to use Photomatix Essentials, since it is not very expensive. Then I do added processing in Elements.

http://www.hdrsoft.com/

Edit: I reread the original posting, and realized you use PSP X3. I used to use version X2 and it had an HDR merge feature. I found this KB link on Corel's site, but it's for version X4. It should give you a good idea of how to use it in X3 as well. You owner's guide for the software should also have info.

KB article on HDR

Dennis