Can NI auto-match best profile when exposure 'pushed'?
Posted: Tue Oct 13, 2009 11:51 am
Canon 50D
DPP 3.6.1
CS4
NI 6.1 64-bit plug-in
I've got a bunch of pictures (500+ after throwing away rejects) that were taken of a high school musical with mediocre lighting. Much of the lighting was from spotlights that changed a lot.
The pictures were taken at iso's from 800 to 3200 iso, and many were significantly underexposed. Also, I did a lot of bracketing the exposure in bursts of three, such as 1.3 under-exposed, zero compensation, and 1.3 over-exposed.
Also, many of the pictures are relatively "busy" without good places for NI to find a good sized square that has no detail. Otherwise, I could rely on auto-detection and let NI measure noise rather than using auto-match.
For many, I did the equivalent of "pushing" the ISO. Back with darkrooms, you might be using Tri-400, and develop so that you got the equivalent of ISO 800. My understanding is that this is roughly equivalent to increasing the exposure slider a stop. With both firm and digital images, the noise increases significantly.
My understanding is that NI auto-matches a profile based on:
1. Which camera
2. ISO
3. How much compression?
4. Resolution
5. Sharpness
6. Exposure
Is there a way that NI can detect how much the exposure was increased in post-processing before the NI step? It seems like the noise can be very different for an image that had exposure "pushed" in post-processing by 0 stops, 1 stop, or 2 stops.
With Canon's DPP (Digital Photo Pro) 3.6.1 , the information may be partly available. With "Image Information On", there are fields for:
* Exposure Compensation
* Autoexposure Bracketing.
The point is that it would be helpful if NI could auto-match and use a profile that took into account "pushed iso" rather than what the basic ISO was. This would be the equivalent of NI determining something like "the picture was taken at 1600 iso, but the best profile-match would be "1600-Plus-Two-Stop-Exposure-Slider-Increase").
However, this doesn't show if the exposure slider was increased from the original image during p.p. That makes me doubt whether NI could auto-match that the exposure slider was "pushed".
I suppose I could keep track of which images were "pushed", and process them in a batch. I would have profile folders for:
* no push
* half-stop pushed
* full-stop pushed
* 1.5 stop pushed
* two stops pushed
I did take pictures of the calibration target that were intentionally under-exposed by one and two stops. Then I corrected the exposure by "pushing" with the exposure slider and built NI profiles from those.
The intention is to have them available to refine the noise-profile-matching. My expectation was that this would work ok if a whole series of images were underexposed by a relatively set amount. I sometimes do this when the lighting is fairly constant, but to get an acceptable shutter speed and f-stop for DOF, I intentionally under-exposre. (but perhaps in the future I should increase the ISO and avoid "pushing?)
However, it becomes less productive when the lighting varies a lot. In a series of images, each can vary a lot from the previous without a useful pattern.
I suppose I could use the CS4 Bridge labels to color-code the relatively degree of "pushing" involved. Or use keywords to identify the amount of positive or negative pushing. I want to use ACR 5.5 to correct the exposure, and then have NI handle them in batches.
Another factor is that I expect to be using ACR 5.5's adjustment brush to "paint-in" exposure compensations for high contrast. In a single image, two actors might be in the stoplight and over-exposed, and two actors might be out of the spotlight and under-exposed. My expectation is that noise would be higher in those areas where exposure was increased. I suppose this would really throw off auto-matching and expecially auto-detection.
A related factor, if ETTR was being used (expose-to-the-right), the actual noise could be significanly less than the ISO would predict. (The image is intentionally overexposed in the camera, then the image is 'reverse-pushed' during p.p. by moving the exposure slider to the left). I suppose this could be termed "negative pushing".
DPP 3.6.1
CS4
NI 6.1 64-bit plug-in
I've got a bunch of pictures (500+ after throwing away rejects) that were taken of a high school musical with mediocre lighting. Much of the lighting was from spotlights that changed a lot.
The pictures were taken at iso's from 800 to 3200 iso, and many were significantly underexposed. Also, I did a lot of bracketing the exposure in bursts of three, such as 1.3 under-exposed, zero compensation, and 1.3 over-exposed.
Also, many of the pictures are relatively "busy" without good places for NI to find a good sized square that has no detail. Otherwise, I could rely on auto-detection and let NI measure noise rather than using auto-match.
For many, I did the equivalent of "pushing" the ISO. Back with darkrooms, you might be using Tri-400, and develop so that you got the equivalent of ISO 800. My understanding is that this is roughly equivalent to increasing the exposure slider a stop. With both firm and digital images, the noise increases significantly.
My understanding is that NI auto-matches a profile based on:
1. Which camera
2. ISO
3. How much compression?
4. Resolution
5. Sharpness
6. Exposure
Is there a way that NI can detect how much the exposure was increased in post-processing before the NI step? It seems like the noise can be very different for an image that had exposure "pushed" in post-processing by 0 stops, 1 stop, or 2 stops.
With Canon's DPP (Digital Photo Pro) 3.6.1 , the information may be partly available. With "Image Information On", there are fields for:
* Exposure Compensation
* Autoexposure Bracketing.
The point is that it would be helpful if NI could auto-match and use a profile that took into account "pushed iso" rather than what the basic ISO was. This would be the equivalent of NI determining something like "the picture was taken at 1600 iso, but the best profile-match would be "1600-Plus-Two-Stop-Exposure-Slider-Increase").
However, this doesn't show if the exposure slider was increased from the original image during p.p. That makes me doubt whether NI could auto-match that the exposure slider was "pushed".
I suppose I could keep track of which images were "pushed", and process them in a batch. I would have profile folders for:
* no push
* half-stop pushed
* full-stop pushed
* 1.5 stop pushed
* two stops pushed
I did take pictures of the calibration target that were intentionally under-exposed by one and two stops. Then I corrected the exposure by "pushing" with the exposure slider and built NI profiles from those.
The intention is to have them available to refine the noise-profile-matching. My expectation was that this would work ok if a whole series of images were underexposed by a relatively set amount. I sometimes do this when the lighting is fairly constant, but to get an acceptable shutter speed and f-stop for DOF, I intentionally under-exposre. (but perhaps in the future I should increase the ISO and avoid "pushing?)
However, it becomes less productive when the lighting varies a lot. In a series of images, each can vary a lot from the previous without a useful pattern.
I suppose I could use the CS4 Bridge labels to color-code the relatively degree of "pushing" involved. Or use keywords to identify the amount of positive or negative pushing. I want to use ACR 5.5 to correct the exposure, and then have NI handle them in batches.
Another factor is that I expect to be using ACR 5.5's adjustment brush to "paint-in" exposure compensations for high contrast. In a single image, two actors might be in the stoplight and over-exposed, and two actors might be out of the spotlight and under-exposed. My expectation is that noise would be higher in those areas where exposure was increased. I suppose this would really throw off auto-matching and expecially auto-detection.
A related factor, if ETTR was being used (expose-to-the-right), the actual noise could be significanly less than the ISO would predict. (The image is intentionally overexposed in the camera, then the image is 'reverse-pushed' during p.p. by moving the exposure slider to the left). I suppose this could be termed "negative pushing".