52 States in 8 Months

How do I make gray pictures look nice?

Posted in Las Vegas to El Paso by Ulf on May 12, 2009

A few days ago I published a grayscale picture, and Flo & Mascha asked my to post-process it a little to make it look more “punchy”.
Normally I do not do any post-processing at all with the pictures you find on this blog. There are a few exceptions, for example when my lens wasn’t clean or when I stitch a bunch of single pictures together to create a panorama. And this will be another exception.

Here is the original picture. It came already from the camera in “gray scales” (can you say this?), so all I did was stitching two shots together:

Flo proposed to increase the contrast a bit. I increased the contrast by 10% and 20% in the following two pictures (100% would yield a b/w picture):

sea_gray_contrast10 sea_gray_contrast20

Instead of changing the contrast, Flo mentioned “raising the black point”. In the next two experiments, every pixel with a brightness of 0.1 or less (0.2 for the second one) is mapped to 0, yielding a total black. The remaining color scale (0.1 to 1.0 or 0.2 to 1.0) is linearly distributed between 0 and 1. Flo, is that what you had in mind?

sea_gray_black10 sea_gray_black20

My amateurish eye thinks that the pictures do already look “more interesting”. Furthermore the 10% increase in contrast is comparable to the 0.1-to-0 mapping, while the 20% increase in contrast shows far less effect than the 0.2-cutoff.

Since the picture was taken around 9am which is neither dawn nor dusk, Flo proposed increasing the brightness. That step has to be combined with the increase in contrast, I think. Here is what comes out when I increase the contrast and the brightness by 20% each:

Or well, we’re in America. Let’s go big. +50% brightness, afterwards putting the black point to 0.2:

Thank you for you advise, Flo and Mascha. I think that the place really got more lively now (although “dull” would have been a pretty good description of my first impression of this place *g*). Luckily there are a lot of pictures from the South West coming up — landscapes where any post-processing could only make things worse (feel free to prove me wrong).

PS: In the case you had other changes in mind, feel free to prepare your version of the picture and leave a comment.

EDIT: The first gimp’ed image came it! Fabi, a nice chap I met in Miami, proposed using the GIMP “Color Curves” function to spice my picture up. The S-shaped mapping function he used also increased the average brightness in the resulting image and increased the contrast. There is something I really start to like about this GIMP function: I understand what I’m doing. If I say “increase the contrast by 20%”, then my only guess would be that they apply some nonlinear transformation until some numerical indicator of the image’s contrast changes to a certain value. Not very specific. The function which Fabi proposed however will directly show you which input color is matched to what output color! Now, this is his result:
seagray_fabiAnd I do not only like the method, I do also like the result. Fabi was more courageous to allow really bright areas in the sky, and I think that this was a good idea. It created a more visible contrast between the sea and the sky.


7 Responses

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  1. Fabi said, on May 12, 2009 at 7:12 am

    Another method I like quite a lot: The Gimp control “Colors->Curves” is great for low-contrast pictures. It’s a matter of finding the right curve, but usually a simple “S”-shaped curve yields really good results. Here is the touched-up version and the curve I used:

    Greez, Fabi

    P.S.: I hope it’s okay for you to put the image on imageshack, if not then tell me!

  2. Ulf said, on May 12, 2009 at 8:29 am

    Wow, thanks a lot! I included you image in my post :-). Yes, Imageshack is totally fine.

  3. stefan said, on May 12, 2009 at 11:26 am

    my favourite is the 20% contrast picture … I even prefer it to the fabi-picture, which seems to have been created using much more brain cells

    you don’t like the nonlinear transformation and the numerical indicator of the image’s contrast changes to a certain value, but perhaps this transformation is some very sophisticated function and perhaps the numerical indicator is very clever :P

    apart from that: stay motivated, this curves are a very strong tool if you know how to use them (^-^) (despite of long hours of editing multiple pictures I never managed to use even a fraction of their potential)

  4. Andreas said, on May 12, 2009 at 12:20 pm

    Wehlans DBV lässt grüßen

  5. Ulf said, on May 12, 2009 at 12:45 pm

    Andreas, do you remember any details from that lecture?

  6. Andreas said, on May 13, 2009 at 4:59 pm

    every single one of course

  7. Ulf said, on May 13, 2009 at 5:33 pm

    You slept during every single lecture, eh?
    Either in you bed at home or on your desk in the classroom.

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