Scan Correct Color Smooth Texture Reduce Noise Remove Dust Repair Crop

I believe this is true for scanning: Do it once and do it right.

My workflow is made up from a set of individual steps. The first step is scanning a photo. My goal in the first step is to produce an image file that matches the photo as much as possible. I then treat that file as an master, and make a copy for post-processing. Further steps in the workflow involve editing the copy. Each step changes and improves the copy until I am finished restoring the image.

History of this Workflow

I used to make extensive image adjustments within the scanning software. I would set exposure control, levels, curves, and sometimes descreening for each scan. I would keep making changes until I was happy. But each change meant a new scan. And if I decided a whole batch of scans just didn't turn out right, I'd scan them all again!

Many weeks and rescans later, I tried something completely different. I separated the scanning process from the restoration process. I first made uncorrected or color-corrected scans using a scanning program, and then I made level and color adjustments and used assorted filters using an image editor. I discovered it was vastly easier to make adjustments after the scan since I avoided having to scan the image again.

With this new knowledge, I saw the light. I changed my workflow to break up the task of scanning into individual steps. My new first step was to get a good scanned image and make a working copy for adjustments and editing done in later steps.

So now I never have to rescan a photo. Yay!

Order of Steps

I've done a lot of testing with noisy photos and determined that noise reduction works much better if performed before dust & scratch removal. The dust & scratch filter softens images too much for noise reduction filters to work well.

Further, I found that noise reduction works much better when the contrast is properly adjusted before using the filter. Using noise reduction filters on low contrast images can smear details.

Good contrast can be set directly, or it can be set indirectly by adjusting levels or curves, lightening shadows, or something similar. Adjusting levels can be difficult when the image has strong color casts, so it's best to correct color first. Color can be corrected manually or automatically, after or during the scan.

So, the preliminary order of the first half of the workflow is:
scan as tiff -> archive tiff -> correct color -> fix levels -> reduce noise -> remove dust

Texture removal is similar to noise removal with the addition of a couple of filters. A blur filter can be used to soften rough texture, but it must be done last. Blur filters soften images too much for noise reduction filters to work well.

If the texture has a regularly-spaced pattern (such as rows of dimples), I have found that it is crucial to use an FFT filter before using a noise filter. If the noise filter is used first, it will distort the pattern making it difficult for the FFT filter to remove.

Removing texture therefore consists of using 3 filters in the following order: FFT filter (only for pattern noise), noise filter, and blur filter. Removing texture should be fit into the workflow before "reduce noise" since the FFT filter must run before any noise filter.

The corrected order of the first half of the workflow is now:
scan as tiff -> archive tiff -> correct color -> fix levels -> smooth texture -> reduce noise -> remove dust

After fixing levels and running filters, it's safe to make any needed repairs to the image. These repairs may include healing brushes, clone stamps, and similar tools. After all repairs are done, the image file should be archived as a tiff and a working copy made for the final step.

The final step involves cropping, resizing, and sharpening. From advice I've repeatedly seen on the web, sharpening should be the very last change made to an image, after an image has reached its final size. Once the final step is completed, the file can be saved as a jpeg or png or tiff as desired.

The order of the last half of the workflow is therefore:
remove dust -> repair photo -> archive tiff -> crop -> resize -> sharpen -> save as jpeg/png/tiff

Time Required for Each Step

The following table and notes are from a number of timing tests I've run.
Step Time
Scan Normal Photo
regular size prints without borders in decent shape [31min/16pix] 		2 min
Scan Abnormal Photo (usually requires reselecting or repositioning)
tiny, misshapen, damaged, or with uneven borders [75min/18pix] 		4.2 min
Scan Photo Again (fast since photo is already positioned and selected)
for making two scans, one straight, one automatically color corrected [6.8min/16pix] 		.4 min
Scan Backs of Photos (jpeg of sheet of photo backs)
for the handwritten names, dates, and notes on the backs of photos [5.8min/16pix] 		.4 min
Correct Color and Adjust Levels for uncorrected photos (using a levels tool)
set of 10 very faded photos, uncorrected (straight) [16.8min/10pix] 		1.7 min
Correct Color and Adjust Levels for corrected photos (using a levels tool)
same set of 10 very faded photos, corrected at the time of scan [7.8min/10pix] 		.8 min
Remove Noise on Grainy or Noisy Photos
set of 19 noisy photos [average of 3 individual filters: 75s, 122s, 118s] 		1.8 min
Remove Dust & Scratches (heavy dust/scratches)
set of 9 older photos with lots of dust or scratches, multiple passes [29min/9pix] 		3.2 min
Remove Dust & Scratches (light dust/scratches)
set of 5 newer photos in good shape, single pass [6.3min/5pix] 		1.3 min
Repair Damaged Photo varies
Crop and Sharpen
set of 10 color corrected photos [2.6min/10pix] 		.3 min

Estimated Time Required for Each Photo

I heartily encourage making and archiving both straight scans and automatically corrected scans, and to scan the backs for handwritten notes.

To greatly simplify the above table, I have found it typically takes about 5 minutes to scan and color correct a normal photo, and to resize and convert it into a jpeg. The 5 minutes includes a straight scan, a color corrected scan, a scan of the photo backs, and final (manual) color correction & level adjustment. In other words, I would allow at least 5 minutes for the first 2 steps and last step of this workflow: Scan, Correct Color, Crop and Sharpen. This estimated minimum time was arrived at by using the above table and adding a safety margin for mistakes and other unforeseen problems.

The table below lists estimated times to scan and restore photos for photos in various conditions. The times in the table below include the scanning and adjustment.
Condition of Photo Est. Time
corrected scan, front only, color correction during the scan, no restoration 2 to 3
straight & corrected scans, back scan, color correction afterwards, no restoration 5
scan & restore noisy photos with light scratches 10
scan & restore noisy photos with heavy scratches, marks, and texture 15
photos that need repair (rips, creases, stains, missing pieces, etc)
this kind of work can be incredibly time consuming 		varies greatly