Anyone done a systematic study of DAC/28mm optimizations in FC?

[Andy Johnson-Laird]

I've seen a fair number of references to the optimization that FC does to images that are otherwise lost if you use FC to save images as DNGs not TIFFs.

Just curious, but has anyone done any systematic measurements/observations of these optimizations?
Or even just anecdotal observations?

I ask because I'm giving serious consideration to using DNGs so that I can get to ACR/PSCS4 ASAP  (I'm also thinking of writing entirely in acronyms, but it's really quite hard). 

Regards
Andy

[NickT]

Well FYI and FWIW I spent alot of time at Kina showing the DAC Corrections  and IMO they are invaluable YMMV.
Nick-T

[Andy Johnson-Laird]

Well FYI and FWIW I spent alot of time at Kina showing the DAC Corrections  and IMO they are invaluable YMMV.
Nick-T

ACK.

[alexkent]

the amount of correction done by the DAC depends heavily on the lens (obviously) and DAC encompasses three types of lens corrections; geometrical distortion, chromatic aberration, vignetting.
with the 28mm the geometrical corrections are pretty significant. without DAC the lens has 'fisheye' style curvature coming in at the corners.
the CA fix is also pretty great, now i look at images i've shot on H1D's (pre-DAC) and i'm always seeing the green and magenta edges.
vignetting fix, you can take it of leave it. i'd like to think i use vignetting (optical or postproduction) as a creative element.

alex.

[Andy Johnson-Laird]

Thanks, Alex. I guess I will elect to live with slooow approach of getting FC to save all the images to TIFFs so I can get to ACR/PSCS4.

Regards
Andy

[alexkent]

Andy,

are you putting your Tif images out of Flexcolor into Adobe Camera Raw before going into Photoshop ?

what do you see as the benefits of doing this ?

(i guess batch dust removal is an example)

alex.

[Andy Johnson-Laird]

Andy,

are you putting your Tif images out of Flexcolor into Adobe Camera Raw before going into Photoshop ?

what do you see as the benefits of doing this ?

(i guess batch dust removal is an example)

alex.

I do it primarily because:
1. It's a way to apply a camera calibration (created using the Gretag Macbeth color target).
2. As far as I know, it's the easiest way to do a lossless aspect-ratio-based crop (no up or down-rezzing, just raw pixels). There may be a way of using Photoshop to do this--I've been told that, if you use the Crop tool and if you omit the "Resolution" value, then the width and height are taken as a ratio -- but I'm not entirely convinced--ACR has an actual "ratio" crop that allows me to get an image with the correct aspect ratio regardless of physical pixels.

The reason why I do this is that I tend to print a lot of 11" x 14" prints to fit inside the Nielsen Bainbridge 16" x 20" metal frames that come with a pre-cut matte -- and I've found that an aspect ratio of 1:0.785 (Portrait) or 1:1.311 (Landscape) then fits into the pre-cut matte with 1/4" borders left, top, and right, and 1/2" at the bottom for print number and signature.

I've developed a bunch of Javascript code for Photoshop that takes my "master cropped" file for images created from any of the camera bodies I use and can then create appropriately sized print/web images, sharpen them for output (PKSharpener) and save them with an appropriate file name. Of course, now I stumbled across the fact that there does not appear to be a 64-bit version of PKSharpener.

I agree that using ACR on a TIFF file is probably not optimal for the H3DII images but it allows a fairly standardised workflow regardless of the camera body that created the images. It was also an act of desparation borne of the realization that I'd been suckered into getting an H3DII-39 without any (at least back then) hope of getting Phocus for the PC. Sigh. 

Regards
Andy