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[Admin Jim]

A rusty old lime plant in Salem

[BBNC]

Jim, I'm interested in HDR, but haven't tried it yet.  I do understand what it is.  Is there any recommended number of exposures for best results?

[Squirl033]

Jim, I'm interested in HDR, but haven't tried it yet.  I do understand what it is.  Is there any recommended number of exposures for best results?

i'll jump in here, if you don't mind, Jim...

BB, the minimum usually required is 3 images, but many people shoot 4, 5, or 6 exposures at different settings. shooting 2 or 3 additional frames gives the software more tone and exposure information to work with, and most HDR software will allow you to work with at least 6 frames. while some people use even more than that, above 6 or so becomes cumbersome to work with, and doesn't really gain you anything. if i'm faced with a difficult exposure and know i'll need to process it as an HDR image, i'll usually shoot 4 or 5 frames. depending on the light, i may shoot more of them above or below the 'recommended' exposure suggested by the camera.

[BBNC]

Thanks for the info, Rocky.  I'll have to try that.

[Squirl033]

one more thing... most folks use the auto-bracket feature to shoot the frames for HDR. if your camera allows it, it can sometimes be faster and more precise to shoot in manual mode and simply move the exposure up or down using the exposure control. on my Canon DSLRs, i shoot in Av mode and use the 'command dial' on the back, and move the exposure value up or down in 1/3 stop increments. i may start 1-2/3 stops underexposed, and work my way up to a stop over, or whatever the lighting dictates, and all i need to do is turn the dial one or two notches between shots.

in full manual mode, if you use AEB, you can also move the entire 'set' of values up or down the exposure spectrum so that you get half a dozen frames all with different values. your first three shots might all fall between 2 stops under and "0", and your second set might be between "0" and 2 stops over. you just have to remember to turn the AEB off when you're done, or you'll wind up bracketing shots you didn't intend to, as i've done a few times!   

[Admin Jim]

Rocky knows of what he speaks. I think the one thing that is important to remember is that the shutter speed needs to remain constant while you adjust the apertures up and down. If you just stay in "AV" mode in most cameras, but do not use exposure bracketing, the camera will adjust your shutter speed each time and you'll end up with three pictures that all are pretty much the same.

CORRECTION!!! CORRECTION!! - YOUR IDIOT ADMIN WROTE IT BACKWARDS. THE APERTURE STAYS CONSTANT WHILE SHUTTER SPEED VARIES!

[Squirl033]

Rocky knows of what he speaks. I think the one thing that is important to remember is that the shutter speed needs to remain constant while you adjust the apertures up and down. If you just stay in "AV" mode in most cameras, but do not use exposure bracketing, the camera will adjust your shutter speed each time and you'll end up with three pictures that all are pretty much the same.

you can shoot in Av mode if you use the command dial (on Canons, anyway), which allows you to quickly and easily override the camera's 'automatic' settings by changing the shutter speed or aperture manually to achieve the exposure you want. it's like shooting in manual without having to switch to manual mode. if you do change the aperture, just be sure you don't move it more than a stop or two either way, or your depth of field will change and you may lose the sharp focus in some portions of the image, which can result in a softer focus than you'd like.

of course, bracketing eliminates this entirely by simply shooting the three frames at the exposure settings you've selected. in Av mode, it keeps the aperture constant, and varies the shutter speed for you to give you the desired +/0/- exposures you select. i tend to shoot using the command dial option, though, simply because i can choose as many shots as i want, without having to go into the menu and change the AEB settings.

[BBNC]

I understand gentlemen, thanks.

[rayman]

Jim:

    I am confused now. I haven't done HDR but hope to soon. You said to keep the shutter-speed the same and vary the aperture.  Since HDR is primarily used with with landscapes and immovable objects, the shutter speed need not matter. However, changing the Aperture will affect the DOF. Am I miss-reading your comment above. I don't have AV Mode on my Nikon so maybe that's why your apples are my oranges!

[SloppyJoe]

Jim:

    I am confused now. I haven't done HDR but hope to soon. You said to keep the shutter-speed the same and vary the aperture.  Since HDR is primarily used with with landscapes and immovable objects, the shutter speed need not matter. However, changing the Aperture will affect the DOF. Am I miss-reading your comment above. I don't have AV Mode on my Nikon so maybe that's why your apples are my oranges!

Hey Ray, Nikon has a mode that is labled Ap. Not sure what model you are using,but you could also check for an auto bracketing in the menu. If you do not have auto bracketing, you could also set it in Ap mode, take 3 photos with out moving the camera, change the EV levels from lighter to darker. You will need a tripod to do this and get a clean photo. If I am incorrect with anything stated someone speak up some so I can be corrected as well.
SJ

[OriginalCyn]

Perhaps Jim or Rocky could post a tutorial on HDR for us all?

[Admin Jim]

Jim:

    I am confused now. I haven't done HDR but hope to soon. You said to keep the shutter-speed the same and vary the aperture.  Since HDR is primarily used with with landscapes and immovable objects, the shutter speed need not matter. However, changing the Aperture will affect the DOF. Am I miss-reading your comment above. I don't have AV Mode on my Nikon so maybe that's why your apples are my oranges!

You are right to be confused. I wrote it backwards.  At least with Canon, if you use Automatic Exposure Bracketing, it's the SHUTTER SPEED that varies, and your aperture stays more or less constant. As you noted, if you vary the aperture, you run the risk of DOF variations.

There's really two parts to creating an HDR image.

1) Take your bracketed shots and combine them in software to create the initial HDR image
2) TONE MAP the resultant image for optimum display on today's hardware.

I'll look at putting a short quick tutorial together that will, of necessity, be rather broad - some cameras can do the in-camera creation of an HDR image with a simple menu setting, others will require quite a bit of manual work.  And even after the HDRI has been created, the tone-mapping part is so dependent on software, personal taste, and what you want the final image to look like that it's hard to describe except with one specific tool, such as Photomatix or any of the dozen or so other HDR processing programs out there.

[rayman]

Thank you Jim for clarifying the subject. If you have a chance would you look at the HDR I submitted the other day. I am unsure if it qualifies as processed. It seemed to simple for me. So I don't think it PP correctly for HDR.Thanks.  Ray