Sigma DP1 B&W in ACR/Lightroom vs Sigma Photo Pro
Sunday, September 21, 2008

I've been testing out the new Adobe Camera Raw (ACR)/Lightroom (LR) preliminary support for Sigma DP1 files. Color results are very good.  They're as good as what I can manage with Sigma Photo Pro (SPP) and with less time and effort.  What about black and white conversions?

First, a few observations about SPP: SPP seems to apply color and luminance noise reduction to RAW files, increasingly with higher ISO.  The one way to get around this is to use the "monochrome" white balance setting, which has three consequences besides converting the image to black and whte.  First, the luminance NR, which otherwise cannot be disabled, is turned off in this setting.  Second, the apparent exposure increases.  It's as if SPP is throwing away light as part of the color processing workflow and makes use of that light during B&W conversions.  I don't know how or why, but it seems this way.  If an image is properly exposed in color, the monochrome WB setting typically requires about a stop of negative EV.  If the color image is about a stop underexposed, the monochrome WB setting usually looks pretty good.  The third "benefit" of the monochrome WB setting in SPP is that "pushed" results look the same as native increases in ISO.  For example, a color image shot at ISO 200 underexposed by two stops and pushed to +2EV in SPP looks blotchy and noisy compared with a color image shot at ISO 800.  However, those two images will look identical (or close enough) using the monochrome WB setting.  For those three reasons, I've found that I get much better B&W results from the DP1 by using the monochrome WB setting in SPP than I do with a color RAW conversion subsequently processed from TIFF to B&W in Photoshop CS3.

In order to demonstrate the differences between SPP and ACR/LR B&W conversions, I'll use two examples taken today.  Both were significantly underexposed and basically worthless in color.  The reader may feel that they are worthless in B&W as well, but this is a technical demo not an artistic one.

The first example is a photo of my son Oliver showing me a massive African bullfrog.  The image was taken at f/4, ISO 200, 1/50s.  Here's what it looked like when opened with native settings in ACR and SPP respectively:

 
  

Here you can see that to get a similar look in ACR and SPP respectively, the ACR exposure is at +2.9 EV (~ ISO 1600 equivalent) whereas SPP is at +1.9 EV:

 
 

The differences in rendition are subtle, even viewed at 100%.  Click the image below to view at the intended viewing size:

 
  

The subtle difference, as I see it, is that shadows are smeared a bit in the ACR version.  This is more evident in the second (bullfrog) crop above.  At any rate, there's little to choose between them.  

Things get more interesting when pushing the limits of DP1 low light capability.  Here is a shot of my two sons taken a few hours ago.  The settings were f/4, ISO 800, 1/50s.  The light was coming from the computer display, and a bit of light through the window behind them.  A you can see from the default color appearance in ACR and SPP respectively below, this was again way underexposed:

 
 

Below you can see that to get a similar look in ACR and SPP respectively, the ACR exposure is at +3.85 EV (Nearly ISO 12,800 equivalent) whereas SPP is at +2 EV.  The brightness of the SPP version is compensated by way of the X3F Fill Light at +0.5, and from the histogram I didn't get the files to match exactly.  Close enough to make the point:

 

Here's the key part.  Click on the image below to see what the files look like at 100%:


To me, the ACR crop is obviously noise reduced/blotchy.  Meanwhile, the SPP crop looks terrible but untouched by NR.  

So which is worse?  Click the below resized crops to get a rough idea of how these would look after processing, printed to about 8x10"  The ACR crop has been sharpened a bit, and the SPP crop has had some Noise Ninja applied. Keep in mind that these are crops from an ~ISO 12,800 equivalent image taken using a pocket camera!

 

I prefer the SPP process as well as the final look.  ACR/LR applies the same sort of mandatory luminance NR to DP1 files, regardless of whether they are processed in color or B&W.  SPP puts all color images through a similar NR process to that of ACR/LR.  Where they seem to differ is that SPP leaves out the NR during B&W conversions, leaving that as an option for later in the workflow.

The DP1 is a very capable camera for B&W work.  My technical examples don't make, and were not intended to make, that point.  For low ISO B&W photography, I'd consider switching to an ACR/LR workflow.  For high ISO, I'll be using SPP.

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