Sepia in RT 5.5

Software RawTherapee
1

RT 5.5 appimage

How do I make a sepia in RT 5.5?

I have my B&W, but I’d like to make a very slight sepia to fade the highlight just a tiny bit and to make the black slightly warmer. I just want something subtle.

I have tried with color toning, but somehow I can’t seem to make things subtle enough. The best I came up with is lab color correction grid, but it’s still too strong.

rt-2019-02-12_10-52

Any better way?

Thanks

Syv

2

Starting with the grayscaled three-channel image, I just use a straight- line curve on the red channel. Drag the lower left control point up the left hand side slightly, ta da, sepia.

3 Likes
3

Sorry but I don’t get it.
before

before-2019-02-12_12-07
before-2019-02-12_12-07905×583 326 KB

after
after-2019-02-12_12-07
after-2019-02-12_12-07855×539 258 KB

I do not see some sepia, it just makes the image mostly lighter.

obviously, I’m missing something and/or do not understand (most likely)

Thanks

Syv

4

I’m not a RT guru, but you might try unchecking Luminosity mode.

5

Just tried without the luminosity checkmark, it didn’t make it sepia, just lighter

Thanks

Syv

6

I don’t have RT with me, but I’ll try to figure it out tonight…

I do this very thing in my hack software quite a bit with my black and white images, also with the blue channel to give a nice ‘Illford’ tone to my steam locomotives. But, my software doesn’t try to save me from myself… :smiley:

7

Sepia toning is a specialized treatment to give a black-and-white photographic print a warmer tone and to enhance its archival qualities.

Going by that definition, start by activating the Black-and-White tool, then give the black-and-white image a sepia tone using any of the color toning tools, and finally, optionally, use a tone curve to reduce contrast.

4 Likes
8
  • you can also use BW HaldClut
  • following what @Morgan_Hardwood said above, I prefer to use the color correction regions tool.
    You can then adjust the intensity of sepia color by using the saturation slider to give a subtle effect.
  • warning: in the Black and White tool, don’t use gamma correction

amsterdam-1
amsterdam-11944×1304 961 KB

amsterdam-1.jpg.out.pp3 (11.7 KB)

1 Like
9

@foto, I owe and apology, I can’t find a way to translate my advice into RT. I’m just not familiar enough with the operations and the pipeline order. So, I’'m going to turn it into essentials of the concept:

Making a color image “black and white” is to modify each RGB pixel so the R, G, and B values are equal, R=G=B. A “tone” such as sepia is essentially a color cast, where one or more of the channels are shifted from the values that render the “normal” color, in this case a shade of gray (R=G=B). So, a simple sepia is to take that R=G=B image and shift the R values up a bit.

Okay, bit of an experiment, I am going to attempt an animated GIF illustration of it with rawproc, my hack software. I’ll open an image, make it grayscale, and apply the red curve I’ve described. The GIF will seqence through those three screenshots with a 5-sec pause in each:

sepia
sepia1200×820 564 KB

Okay, the GIF seems to sequence okay in Chrome; let me know if it doesn’t in your browser. So, here’s what’s going on:

  1. Opened file: this is a JPEG, but that doesn’t really matter once opened as rawproc turns it into a floating point array of RGB pixels. The histogram is of that floating point image. Now, as I add tools, the list at the top-left will grow downward, and the tools will be applied to the original image in that order.
  2. Gray: This tool “desaturates” each RGB pixel like I previously described, R=G=B. The sliders control the proportion of each channel that contributes to that R=G=B value. The histogram is blue because all the channels are now equal and the blue one is in front. The important thing is that it’s still a three-channel image.
  3. Red Curve: So, with the previous tool providing the three-channel grayscale image, the red curve now makes each R value just a little bigger than the others, which are still G=B. The histogram shows that relationship; now, the red line moves out from under the blue line “to the right” of the others. And now, the image takes on a red cast, which I (probably somewhat delusionally) like to think of as Sepia. :smile:

The reason I’m taking you away from RT for a bit is that I’ve found this generic concept to be important to really understanding the R,G,B relationship that comprises a color, and how curves can do more than just lighten or darken an image. “Sepia” is just a color cast, that is, a shift in one or more of the channels from what produces the “normal” image. Whatever a tool that represents itself as a color modifier does, this is its essential effect.

For me, this concept hit home when I was studying color negative conversion. That orange cast in a color negative is just that, a shift in the red and green channels off what you want the colors to be. So, for all the reading I did about film emulsions and such, the essential operation to subtract that cast from the image is to shift those channels back to the place where they represent “normal”, and per-channel curves not much more complicated than the “sepia” red-shift do the trick. We’ll save that for a different GIF… :smile:

Back to the RawTherapee channel, now…

2 Likes
10

What I ended up doing is:

I did try the color correction regions but I couldn’t figure out how to use in the B&W, so I ended up using color balance shadows and highlights with a very low strength.

rt-2019-02-13_08-54
rt-2019-02-13_08-54992×579 343 KB

If there’s a better way (for better sepia) please let me know.

Thanks

Syv

11

After conversion to B&W, I use it like that
CT

Just use saturation slider to weaken the tone.
I cannot say if it is better. It’s a matter of taste.
I scanned 2 months ago, very old family photos from XIX century. I can say that there are different BW tones depending on the development process. Even sepia tones are not all identical, some lighter some more intense.

12

That’s what I tried, except my saturation was less in -30s range, but I couldn’t get any effect. I’ll try again tomorrow.

Thanks

Syv

13

Perhaps these (sepia) HaldCLUTs might help you?
http://www.digicrea.be/haldclut-set-style-a-la-nik-software/

Have fun!
Claes in Lund, Sweden

14

Could you upload the corresponding PP3?

15

Thanks, I figured it out why I wasn’t getting any effect.

I was circling the white point too fast through the red, the blues and the green squares:alien: I just tried again and now if I stop at each trying point it works.

Thanks

Syv