Mute Colors and Portra-esque Curves ???


The quote below is from this article:

  1. I assume that there are many ways to accomplish this; but, how did you mute the colors in that particular image and what are some of the other ways to mute colors ?

  2. Please expand upon this “Portra-esque” color curves.
    Am I correct in assuming that “Portra” is “Portrait”?
    How is that accomplished ?

Do you have comparison samples of that last image before and after muting the colors and before the Portra-esque curves ?
Were these steps done before or after the Freaky Details ?

Thanks for reading and all help is appreciated.


Presumably: No, you are not correct :slight_smile:

Have fun!
Claes in Lund, Sweden

(Elle Stone) #3

Above is a very old website (as digital photography sites go), well worth exploring. There are some downloadable GIMP curves for the various film types that Petteri was aiming to emulate with Curves.


[quote=“Claes, post:2, topic:9807, full:true”]Presumably: No, you are not correct :slight_smile:

Oh my; that’s a first for me…

Thanks for enlightening me.
I know but very little about film; I only ever bought whatever was cheapest at the drug-store for our old $29.95 fixed-focus camera.
Although I am way behind you guys, I am miles ahead in photographic knowledge compared to where I was in December 2013 when I got my wife her big girl camera.


[quote=“Elle, post:3, topic:9807, full:true”]Above is a very old website (as digital photography sites go), well worth exploring. There are some downloadable GIMP curves for the various film types that Petteri was aiming to emulate with Curves.
Thanks; I will check it out.

EDIT: >>> I see three choices; For my uses, 64-bit Windows 7 and GIMP 2.10.6, which download do I need ?

(Elle Stone) #6

Hmm, my apologies, I don’t understand the question. There is a link at the bottom of the page for downloading GIMP curves:

The article is very old - there’s no date at the top but I remember reading this post (and the rest of the website) not too long after I got my first DSLR, which was summer of 2007. So I’m guessing these curves are for GIMP-2.6? even earlier?

@patdavid, @Ofnuts, other long-time GIMP users - can GIMP-2.10 open and use Curves from earlier versions of GIMP? And where on Windows does the user put downloaded Curves?

Also, can GIMP load and use old-style PhotoShop Curves? Seems like I read somewhere that it could, but I’ve never had any reason to do so.

@BuckSkin - the Petteri article is very careful to make it clear that these Curves are at best an approximation. There are now “LUTS” for various film stocks, that can be applied using PhotoFlow, G’MIC, and other editing programs. I don’t use such LUTs so I don’t have a complete list of such software, but if you are interested in experimenting with film emulation, a lot of people on the forum can point you in the right direction. @Claes already gave one link.

These film-emulating LUTS and Curves are not magic bullets, possibly you might get further, faster, by experimenting with Curves until you see something you like.

(Glenn Butcher) #7

The files in the .zip file have 1/2007 dates.

I downloaded the .zip, it contains 4 .acv files corresponding to the blog post. These are Photoshop curve files, and their format is described here:

Pretty easy to read, it’s just a successive read of short integers with the following sequence: version, count of curves,(curve1),(curve2)… Here’s what’s in the crossprocess.acv file:

$ ./acvdecode.exe crossprocess.acv
Version: 4
Number of curves: 5

Curve 0 is rgb, 1=red, 2=green, 3=blue, 4=alpha?, and I have the points listed in x,y order.

Note that your mileage will vary, as the spline algorithm used in the various softwares will yield slightly different slopes at given points. I put these into rawproc, and they yielded a transform similar to what the blog post shows.

Edit: here are the others:

$ ./acvdecode.exe proviaesque.acv
Version: 4
Number of curves: 5
$ ./acvdecode.exe portraesque.acv
Version: 4
Number of curves: 5
$ ./acvdecode.exe velviaesque.acv
Version: 4
Number of curves: 5

(Elle Stone) #8

Hmm, that seems surprising that the curve files aren’t actually GIMP curve files, given the text in the article’s link to the zip file. Maybe I shouldn’t have posted the link at all - my apologies! But I always did like that website.

(Glenn Butcher) #9

Ah, that’s what I get for just going for the first link. Just a little further down, he has links to GIMP, and LR files. He also makes the statement, “I strongly encourage you to tweak them to make them your own – and explore whole new ways of manipulating color and tone with curves. It’s much more fun that way.” - is that a sufficient license?


I believe I must have stepped off in the deep end…

I appreciate the help and info.

I re-read and it is beginning to sink in.


0-3 are correct. I am also guessing that 4 might be alpha (opacity or fill). It is possible that it is a stand-in for when the image type is CMYK, in which case the numbers would be in percentages. This is going by my distant guess-memory of PS. :sweat_smile:

Also, the PS curve is allowed to have up to 14 point-pairs or something like that.

(Glenn Butcher) #12

From the thread, I’m going to assume you’re new to this, and may not have understanding of some of these tools. So, if you’re familiar with the concept of an image being a width x height table of RGB values called pixels, changing those is often done with a curve. A curve is just a line that says, ‘for every x, use the y instead’. The math wonks call that a ‘transfer function’, makes sense as the line describes a function to use to translate image values from their original to something else. Most of the image editing softwares have a curve tool somewhere.

The basic use of a curve is to alter the overall tone of the image, make parts brighter or darker. The curves we’re talking about here are ‘per channel’ curves, where the curve is only applied to one of the R, G, or B channels. In doing so, you alter the colors of the image, and the particular curves in the previous post endeavor to alter colors to look like various film stocks. Look-up-tables, or LUTs, do the same thing, except they’re not restricted to the shape of a curve. And they’re even simpler than a curve, just a table where you look up the existing value, and then replace it with the lookup value. Well, the software does that…

Note that the curves I posted above are just a few points, the software fills in the rest of the curve with a spline algorithm. Those can differ from program to program, so using a Lightroom-originated curve will probably look a little different in GIMP. Lookup tables are more portable in that regard, but their file format needs to be common between softwares.

You may already know this, but I didn’t want to assume…


Tons of tutorials here:


It is safe to assume that I am not yet very well versed in a lot of this and actually using curves with any idea whatsoever of what I am doing is very new to me.
I am learning and I appreciate all the teaching I can get, even if it does get a bit over my head sometimes.


Thanks !

(Glenn Butcher) #16

I was where you are about three years ago. Trying to make decent pictures out of Nikon D50 JPEGs using Picasa. Man, hadn’t really thought about it 'till now, I’ve come a long way, in no small part to the folk here. This is a good place to learn deep…