pknight
Member
- Joined
- Jul 18, 2009
- Messages
- 82
- Location
- Mid-America
- Lightroom Experience
- Advanced
- Lightroom Version
Victoria Bampton mentioned on her website that the base exposure is not needed to merge to HDR in LR 6/cc. The notion is that, in a 3-exposure bracket situation, you only need the over- and under-exposed shots to create the entire HDR dynamic range. I played around with this, and found that it generally works, and concluded that I will never do things this way.
First off, it does seem to work in terms of dynamic range. Just as with three bracketed shots (-2/0/+2), when you only use two (-2/+2) exposures the resulting LR 6 HDR looks just like the original base exposure (0) before making adjustments. The HDR image based on two exposures is roughly the same size as one created with all three exposures (in fact, slightly larger in my case), and the Develop module adjustments have the same effects on both images.
The problem is that if you are in a situation where you need to use higher ISO settings, the two-exposure HDR is likely to be noisier in the midtones. I was bracketing 3 shots at Eastern State Penitentiary in Philadelphia. Some of the cellblocks are completely abandoned, with only skylights for illumination. This results in very high contrast between the skylights themselves and the shadows almost everywhere else. With no tripod, I was hand-holding these brackets, and to keep the shutter fast enough I had to use ISOs up to 3200. My three-exposure HDRs look good, but there is substantially more noise in the two-exposure images. This makes sense, as LR is having to boost the underexposed image to retrieve this part of the dynamic range, and that leads to noise.
Since my camera (and all cameras, I believe) always shoots a base exposure when bracketing, I see no advantage to creating HDRs without using that exposure, and in some situations there is a penalty for doing so.
First off, it does seem to work in terms of dynamic range. Just as with three bracketed shots (-2/0/+2), when you only use two (-2/+2) exposures the resulting LR 6 HDR looks just like the original base exposure (0) before making adjustments. The HDR image based on two exposures is roughly the same size as one created with all three exposures (in fact, slightly larger in my case), and the Develop module adjustments have the same effects on both images.
The problem is that if you are in a situation where you need to use higher ISO settings, the two-exposure HDR is likely to be noisier in the midtones. I was bracketing 3 shots at Eastern State Penitentiary in Philadelphia. Some of the cellblocks are completely abandoned, with only skylights for illumination. This results in very high contrast between the skylights themselves and the shadows almost everywhere else. With no tripod, I was hand-holding these brackets, and to keep the shutter fast enough I had to use ISOs up to 3200. My three-exposure HDRs look good, but there is substantially more noise in the two-exposure images. This makes sense, as LR is having to boost the underexposed image to retrieve this part of the dynamic range, and that leads to noise.
Since my camera (and all cameras, I believe) always shoots a base exposure when bracketing, I see no advantage to creating HDRs without using that exposure, and in some situations there is a penalty for doing so.
