In a thread on Photography-on-the.net a while ago, someone mentioned reading some advise to set black and white point to 5% and 95% respectively. That’s approximately RGB values (12,12,12) and (242,242,242). Otherwise, shadow and highlight detail would be lost in print.
My first thought was “no way”. After all, white is 255, right? I’d say that’s what printing colormanaged and .icc profiles are for.
I’d accept a bit of a loss, but not thàt much…

So I started to search the web.

Whàt?

One source of the advise was at www.lynda.com: Prepress Essentials by Taz Tally.
He was talking about offset printing. There was also an example about Newsprint. According to that, for a (hypothetical) example where the newspaper press could print a minimum white highlight dot of 20% and a maximum shadow below 80%. The tutorial proceeded to adjust output levels similar to this:

According to the tutorial, you’d be preserving highlight and shadow detail as much as possible for those particular presses.
Yeah, right. What highlights and shadows? They all became midtones…

Gray

I’ve taken a black and white image of mine, since that tutorial was also using a b&w image, and adjusted the shadow and highlight values according to that tutorial. The red dots in the middle image represent the picked black and white point.
Negative scan of Popa Chubby in Atak, 1995. Left to right: Original, for “commercial press” and for “newspaper press”:

If I softproof the rightmost image for “Japan Color 2000 Newspaper” (the only “newspaper” profile I could find in PSCS4), it goes to hell in a handbasket…
Frankly, my first thought was the author went nuts.
Then again, this is Lynda.com, right? Maybe I just misunderstood. Or the file was sent straight to the newspaper press? (without color management)

Another tutorial

“Desktop Printing Techniques” by Chris Orwig, also on Lynda.com, made one point clearer: The 5 and 95% figures are a starting point, and you should test with your own printer / paper / profile. That makes perfect sense.
He also mentioned “accurate detail” and “relevant white / black detail”, where Taz Tally mentions it, but then sets black and white points that I would let clip: Mr. Orwig is more rational in picking the points he chooses for the color sampler tool. (Not the first highlight appearing, but actually something that you want detail in.)
Okay. Obvious: If you have blown whites, then guess what: They are not meant to show detail. No point in setting a white highlight at (242,242,242) nor a deep black shadow at (12,12,12). But that makes it quite personal: What is “meaningful detail”?

A few “Gotcha’s”

The tutorial then goes on to set the color sampler values to read out as grayscale.
No idea why, and not the best option IMO, since the “gray” readout in the info palette is dependant on the settings in the PS color settings for “Gray”.
And guess what: “Europe general purpose” uses Dot gain 15% where “North America general purpose” uses Dot gain 20% for gray working space. Not a huge difference in this case, but one to know.
Also, why not just use the RGB (or HSB) values? They remain constant whatever color settings. Better yet, use LAB values: They change as the luminance changes: quite a difference between (12,12,12) in sRGB and the same value in AdobeRGB (Give it a try)! So keep in mind your document color space!

The “Gotcha’s” visualised

To demonstrate those issues, here are a few screenshots of 4 color samplers I placed in 4 neutral gray patches of a document (the test print I’ll use later on).

All this also speaks in favour of doing your own tests: Your workflow is probably different from mine, or that of the Lynda.com instructors for that matter. As is your definition of “meaningful detail”.

Let’s stop theorising already!

As easy said as done.
So off to search the web for a test image.
I found this nice test image (and description how to evaluate the print) here

Test print: some thoughts.

I usually use AdobeRGB.
The image is in ProPhotoRGB, which gives the “number” patches a little different meaning: A ProPhotoRGB value of (6,6,6) I can distinguish quite well from pure black. In an AdobeRGB document, I have to look hard. In an sRGB document, it’s quite obvious. Similar, ProPhotoRGB (253,253,253) is less easy to distinguish from pure white to me then the same value in AdobeRGB, while sRGB is easiest. The differences are quite subtle though.
The LAB color pickers came in handy here: I wasn’t going nuts, there is a slight difference.

Now that is cleared up…

Lets get printing

I used the Epson R2880 with Epson Premium Glossy Photo Paper.
Color settings in PSCS2 printing dialog:

Colormanagement off in the printer driver of course.
I used the .icc profile downloaded from the Epson website.
There is one profile provided for that paper. The printer driver however, has a few settings that might influence how much ink is laid down on paper:
Photo – 1440dpi vs. SuperPhoto – 5760dpi and “high speed” on or off.
I decided to use an extra sheer of paper to see what the differences were.
I first printed 5760dpi with High Speed on (since I never turn that off anyway) using Relative colorimetric and Perceptual. Black Point Compensation was turned on.

Relative Colorimetric vs. Perceptual

In this test image, the biggest difference is that Relative Colorimetric was a bit more saturated in red and green, but showed blue a bit more purple. Maybe because of that, purples also look a bit more saturated. Unexpected (to me) was that oranges seemed actually more saturated using Perceptual.
Relative colorimetric (with BPC) has a touch less separation between absolute black and (6,6,6)
The softproof showed all of these differences as well.
So I decided to use Perceptual for the second set of prints: 1440dpi with High Speed on and off.

What were the differences?

Not a heck of a lot. In all “Perceptual” prints (6,6,6) is barely visible. And I do mean barely. Relative colorimetric is a touch darker even: It’s more of a “I think I might see a difference” there. I cannot see (4,4,4) in any of them.
I don’t think I see a visible difference between 1440dpi and 5760 dpi, nor between high speed on or off. Yes, I did use a loupe.
Maybe the absolute black is a tiny bit denser if 5760 or “High Speed off” is used, but frankly, I’m not sure (comparing the two absolute black patches in the top right, holding them right next to each other in good light).
A measuring device would be needed to make sure. This is also the “I think I might want to see a difference” category.
The grayscale image is neutral to my eye. There might be tiny color shifts in the dark patches, but that could be my eyes playing tricks. If you need absolute neutrality you might want to test, but for my uses, the B&W is excellent.
No use in posting (scans of) prints, since you really need to see this for yourself. Take my word on this.

So. What did I learn?

The softproof is surprisingly accurate.
I cannot distinguish anything darker then L=1 (LAB color picker) in print.
I cannot distinguish anything lighter then L=99 (LAB color picker) in print.
That is ProPhotoRGB (6,6,6) and ProPhotoRGB (252,252,252) respectively.

That’s fairly close to what I see on screen on my CRT in the highlights, with a bit loss of detail in the shadows. I might want to compensate for that.
A good way to do that is described in this video by John Paul Caponigro.

If I have an image with very deep and important shadows, I might try a test print. But for my normal (even critical) printing, I can trust the softproof: If I see detail on screen, I’ll see it in print. And I’m not all that concerned about the absolute deepest maximum black. Since I don’t consistently see the difference anyway.

Conclusion

I certainly do not want to limit myself to a brightest highlight of 95% for my inkjet printing. So I’ll take the 95% in the tutorials with a grain of salt. I did find, when examining a random bunch of images I processed using my normal workflow, that most images have meaningful detail at about that value. So the tutorials at Lynda.com are right in a way, but could be more accurate.

I’m still very much in doubt on the “Newspaper Press” image that more or less caused this blogpost however…
If anyone has good info on that, I’m all ears.

Further reading

Some excellent resources on printing and related stuff:
http://www.johnpaulcaponigro.com/downloads/technique/technique.php#printing
http://www.northlight-images.co.uk/article_pages/black_and_white_test.html
http://www.northlight-images.co.uk/article_pages/test_images.html
http://www.outbackprint.com/printinginsights/pi049/essay.html
http://homepage.mac.com/billatkinson/FileSharing2.html

Lightroom 2 has two kinds of sharpening: Capture sharpening and output sharpening. Capture sharpening is used to neutralize the blurring caused by the Anti Aliasing filter in your camera.
Output sharpening is dependent on output (print or screen, what size) and meant to overcome the softening caused by resizing or happening when printing.

Differences

Output sharpening in Lightroom is simple: You get 4 options when you export the image: Off, low, standard or high. All else is taken care of by Lightroom. Ease of use for sure. Drawback is that you cannot preview it, so you’ll need to experiment a bit. After that, it’s “set and forget”.
Capture sharpening on the other hand, requires a bit more user interaction. The settings will depend on camera used, subject and personal preference. You can preview it, but only at 100% or higher magnification. So you either need to zoom in, or you can view sharpening in the microscopic small “preview window” Lightroom 2 has for this purpose.
(There is off course the workaround I mentioned in an earlier blog post)

The “Detail” Tab

…in Lightroom is where it’s at: You get 4 sliders for sharpening: Amount, Radius, Detail and Masking.
Some of these are quite self-explanatory if you know a bit about digital imaging, the others might be new to you. Let’s go over them one by one, using this image:
Notice I have the small “preview” window in the detail tab open. If I didn’t, Lightroom would show an exclamation mark, signifying that “a zoom level of 1:1 or greater is required to see these effects”:

Amount and Radius

These two are pretty obvious: Amount lets you set how much you want to sharpen. Scale goes from “0″ to “150″ (Which is red for a reason: In most cases it will be too much). The default setting is “25″.
Radius lets you set how wide you want the sharpening halos to spread out. Scale goes from 0.5 to 3. Default setting is 1. A higher setting will give you wider sharpening halos.
As with a lot of sliders in Lightroom, you get some “visual help” when you press the Option (Alt) key:
Press Option while sliding the Amount slider, and the image goes grayscale, to better show what the sharpening does to the luminosity values in the image.

Press Option while sliding the Detail slider, and you’ll see just the sharpening halos you are creating.

Detail and Masking

Detail (0 to 100, default 25) suppresses these halos.
A setting of 0 will undo quite a bit of what you did in the above sliders. Again, pressing Option while sliding will give you a fairly accurate idea of how much detail you’re allowing to be sharpened.

Masking does exactly what the name implies: It builds a mask on the fly (which is pretty nifty if you ask me) The default of 0 masks nothing so everything is sharpened, the maximum of 100 will sharpen only the big edges in the image. Press Option while adjusting the slider and, contrary to the other settings above, you’ll be shown the mask, not the effect on the image. Probably Adobe figured that it was less ambiguous that way. (And they were right)

Noise Reduction

… is also present in the Detail tab.
There’s a slider for Luminance NR and one for Color NR.
Color noise consists of randomly colored pixels in an image. Luminance noise is more like “film grain” and less of a problem in my opinion.
That’s good, since in most cases, Color noise is fairly easy removed in Lightroom. Luminance Noise reduction is not. At least, not without loosing detail in the process.
Unfortunately, the Lightroom engineers didn’t provide a “visual aid” for noise reduction, so you’re down to good old WYSIWYG.

Here’s the image again. First without sharpening or noise reduction (notice the “switch” in the top left of the “Detail” tab is in the “off” position):

Next, with sharpening but without Noise Reduction. Pretty big difference.

Let’s see what just Color NR does. Notice the random “blobs of color” that were present in the previous image are about gone. And that with a fairly low setting:

Finally. with both Color and Luminance NR. Notice we are already losing detail in the last, while there’s still Luminance noise present.

Finally, here is the exported image, with “standard” output sharpening for screen:

Hope this has shed some light on the subject of sharpening in Lightroom.

Adobe Photoshop Lightroom, like many other Raw converters, has a clipping warning.
The purpose of it is to give you a visual warning (apart from the histogram) of what parts of an image might be clipping.

What is clipping?

A pixel is clipping when it reaches a value of 0 or 255 in one or more channels, and “should have gone further”. Since it cannot go lower then 0 or go higher then 255, it remains at those values: Detail is lost if one or two color channels clip, part of the image is solid black or white if all 3 channels clip.

The effect of color space

As with anything in digital imaging, the color space used has a big influence: A wide gamut color space (such as ProPhotoRGB) will have lower values for the same color then for instance sRGB. So a color that is clipping in sRGB, need not be clipping in ProPhotoRGB!
This color for instance, has sRGB values of (250,40,30). The ProPhotoRGB values are (177,76,36) for the exact same color.

This means that you have a lot more “headroom” in ProPhotoRGB before you hit the “clipping wall”.

So what?

Lightroom uses MelissaRGB internally (ProPhoto RGB with sRGB Tone Response Curve).
The histogram in Lightroom is based on its internal working space. So when you are exporting images for a web gallery, the images might be clipping big time while Lightroom is not warning you!

An example

I opened a DNG file in Lightroom 2.4 and in ACR 5.4. These have basically the same raw conversion engine. The exact same settings were used in both Raw converters.

Here is the image, histogram and clipping warning in Lightroom. (click image to open bigger).
Almost no clipping indicated (It makes no difference what output color space you choose): Just a bit in the lower right that goes almost black, and absolutely no clipping highlights according to Lightroom:

Here is the image in ACR 5.4. Output color space is ProPhotoRGB: About the same clipping warning Lightroom is giving.

Here is the same image in ACR 5.4. Output color space is sRGB: major clipping!

For reference: Here is the image exported out of Lightroom: Clipping indeed:

Workaround

Is there a workaround? No (except using ACR that is).
Simply sad said, the only thing you can do is watch the histogram, guess, and use your eyes. If your screen has close to sRGB gamut, clipping in sRGB might also be visible on screen (as can be seen from the above screenshots in Lightroom).
If you use a wide gamut screen however, you might see quite a difference between the Lightroom “Develop” module and the actual exported image…

for a web gallery.
Normally, Lightroom will only let you preview sharpening and noise reduction at 100% view. This is a good thing™ in my opinion, since it is capture sharpening, meant to negate the effects of an anti-aliasing filter in front of the sensor. You’d get all kinds of moiré without an AA filter, as can be seen in the hilarious story Eamon Hickey wrote about the NC2000.
Since the AA filter softens the image a bit, you need to sharpen it. This is input sharpening. So it should be judged at 100%. Unlike output sharpening, which is better judged at reduced size, at least: For print. For web view at 100% and WYSIWYG.
Or is it?

A workaround

I recently was processing a few ISO 6400 images, which had severe noise in them. Here I ran into the problem that the NR isn’t shown at “fit window” view. So I had no way to judge what the images would look like online.
(all images can be clicked for a larger version)
This is the image as shown in the develop module:

This is part of the image at 100%:

Clearly, no NR is shown in the “Fit screen” view.
What works however, is to create a 1:1 preview (In LightRoom > Library Module > Library > Previews > Render 1:1 previews), then look at your image in “Loupe” view (shortcut: “E”) at fit to screen. Bingo. Both input sharpening and NR are applied. There is no way to get LR to preview output sharpening.
This is the image at fit screen in the Loupe view before and after creating a 1:1 preview:

Web Gallery

The beauty of this is, that it also works for the web gallery: If you preview it in LR after making 1:1 previews, you will see the image as it goes online (minus the output sharpening that is)

The image in the web gallery preview in LR, before and after creating a 1:1 preview: An even bigger difference:

This is the final image as it was exported by LightRoom. Inclusive output sharpening.

Pretty neat, huh?