Interesting thread.
Does anyone have any thoughts about at what stage of the digital workflow it's best to carry out perspective / lens distortion correction? ie Before or after other retouching & colour / curves corrections etc.
Graeme
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If CA is present in the image, it will be made worse by any geometric alterations, sharpening, etc., so you want to get rid of that right away. Ditto on vignetting. I would definitely do lens correction before perspective. If you have a lot of barrel distortion for example, it will be difficult to evaluate the perspective accurately.
Here's my order of operations when using Lightroom/Photoshop:
1. Lightroom
a. Assign a camera calibration profile, if not handled automatically.
b. Adjust the white balance.
c. Use the tone controls to get the white point, black point and gamma close to final values. At this point, I err on the side of eliminating any clipping.
d. Level the image if needed.
e. Adjust the CA correction (Easier to do if the white balance is already reasonable; steps e., f. and g. should be done at high magnification).
f. Adjust the noise reduction controls (If the noise is really serious, skip this step in favor of more powerful NR tools in Photoshop. If this is the case, be very careful with the next sharpening step to not make the noise even worse).
g. Adjust the sharpness controls along "capture sharpening" guidelines.
h. Adjust the presence controls.
i. Re-evalute color and tone and adjust as necessary.
2. Photoshop
a. Immediately after opening, use NR tools if needed. Consider using masks or layers to confine heavy NR to appropriate areas, such as skies.
b. Use PTlens plugin to remove lens distortion.
c. Perform selection type adjustments (local color corrections, etc.), and curves adjustments. Depending on what I'm tryng to accomplish, I might switch to Lab color at this point.
d. Adjust perspective.
e. Crop.
f. Perform "creative sharpening."
g. Look at color and tone again.
h. Perform output sharpening.
Consider that everything in that workflow, except for 2.c., 2.f. and 2.h., can be done in DXO optics on the raw file, nondestructively. For example, you can go back and alter the noise reduction settings if it looks like there will be too much blurring. The lens correction step, including CA correction, is completely automatic, and requires no user intervention. If Lightroom could do really good lens correction (distortion, not just CA and vignetting), I might not need DXO. I think what the world really needs is a DXO plugin for Lightroom.