HDR at night

[KaPOWitsCHRIS]

So I've had a quick search around here, and on Google and I can't find anything particularly useful (unless I've overlooked it).

So I know in HDR you take photos at different exposures usually -2 0 +2, but at night, how do you work out what + 2 is? Like, in the past I've had to use 30 seconds just to get correct exposure for 0 so what would be +2 of that?

I hope someone understands what I'm on about, can't really explain it well >.<

 

[analog.universe]

Exposure compensation is measured in stops, and each stop is a doubling of the amount of light. So, 30 seconds +2 stops = 30 * 2 * 2 = 2 minutes. 30 seconds -2 stops = 30 / 2 / 2 = 7.5 seconds.

 

[KaPOWitsCHRIS]

Ahh, thanks! I'm still fairly new to using the manual settings.

 

[480sparky]

The way I'm starting to do HDRs, day or night, is to forget a rigid set of numbers (-1/0/+1, -2/-1/0,+1,+2) and meter specific areas of the scene. I meter the darkest portion of the scene, meter the lightest portion, and take a frame for every EV from one end to the other.

So if I decide on ISO 200 and f/8, I meter the darkest part and let's say it need to be 2 seconds. Now the highlights read 1/250. So I shoot 2, 1, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125 and 1/250. At this point, I don't care how many shots there are.... odd or even, or what the camera meter reads for 'EV0'. I know I've got enough NEFs to cover the dynamic range of the scene.

If I have the time & the subject is still enough, I'll CMA and take 4 and 1/500. If things are moving fast and I can't take a cardload of images, then I'll fall back on -2,0,+2 AEB that's available with the push of one camera button.

As for the OPs question, if 30 seconds is your EV0, then it's just mathematics from there. If you want a 2-stop HDR, then you need to multiply 30 seconds by 4 (2 stops)..... you end up with 2 minutes. Now it's a matter of whether your gear is capable of that exposure time.

 

[DiskoJoe]

you dont have to use the standard -2, 0, +2 for hdr everytime. you just need a high, low and mid to use for blending. You can fake it too if you have photomatix. Just use your 0 shot and increase the exposure in PS to +2 and one to -2 and use those for the hdr blending. It will come out about 99% as close as the real thing.

 

[spacefuzz]

You can spot meter darks and lights and then adjust/shoot accordingly. Will guarantee you great results because you know you then have the entire range.

I'm lazy though and shoot an auto bracket of three and look at the histograms. If I missed I adjust exposure compensation a stop and reshoot, repeat.

 

[Compaq]

you dont have to use the standard -2, 0, +2 for hdr everytime. you just need a high, low and mid to use for blending. You can fake it too if you have photomatix. Just use your 0 shot and increase the exposure in PS to +2 and one to -2 and use those for the hdr blending. It will come out about 99% as close as the real thing.

I disagree, one exposure HDR won't be near as good as multiple exposures.

 

[KmH]

you dont have to use the standard -2, 0, +2 for hdr everytime. you just need a high, low and mid to use for blending. You can fake it too if you have photomatix. Just use your 0 shot and increase the exposure in PS to +2 and one to -2 and use those for the hdr blending. It will come out about 99% as close as the real thing.

More like 40%, than 99%, and that's if you have a Raw file to work from.

If all you have is a JPEG, forget about it.