Adventures with raw, part 3 – make your own ICC profile

I wrote in my last post on working with raw files that I’d ordered an IT8 target for making an ICC profile. The target is pictured on the left. It doesn’t look like much for about £60.00, does it? Of course the expense comes from the precision needed when making it and then sampling the colours in order to make the reference file.

The way to use it is, you take a picture of the target and then use a piece of software to compare the colour values from the picture to the ones in the reference file in order to produce the profile. At least that’s what I think you’re supposed to do. I haven’t been able to make a decent profile yet, so I might be going about this the wrong way.

Anyway I had a Kodak target so I downloaded the reference file from their FTP server. I was using the Lprof program to generate the profile.

Here is the picture I was testing with. The one on the left is without any profile, while the one on the right is using the Nikon D80 profile and brightness correction.

I photographed the target and then loaded it into the Lprof program, along with the reference file. I then had to place marks at the corners of the colour grid. Lprof then put the green marks where it thought each colour square was. I then hit the create profile button and it started to do its stuff.

Each time I ran the program I got a warning saying there were inconcistences(sic) found and that I should check the target. Unfortunately it didn’t say what I should be checking for, nor was I able to find anything on the interweb.

This was the result of applying the profile. Not exactly an improvement. Of course I realised that this was due to brightness curve still being modified.

So I reset the brightness to the default value and got this. Better than the last one but still not what I want.

I read through any documentation I could find online and soon realised that I had placed the lower markers in the wrong place. I had thought they went on the small squares just below the colour block, when actually they went below the grey scale bar. I fix this and increased the quality of the picture and tried tweaking the settings but I wasn’t able to improve much on that last picture,

So it looks like I bought something of a white elephant. Hopefully as I improve in experience I’ll be able to make a profile which I can use to get good conversions. Ah well, there’s no sense crying over every mistake, you just keep on trying till you run out of cake.

Adventures with raw, part 2

I wrote before about using the conversion tool to turn a raw file into a jpeg or other format. This is the most convenient way. Just select all the files you want to convert then run the tool in batch mode. Then you just leave the computer to do its thing. The problem is, after letting the computer process all the pictures you could easily come back to find they’re too dark, like with these pictures.

These were done with the brightness setting at 1.25.

I tried again with the brightness set to five. This time the pictures aren’t so dark, but still didn’t look right.

There’s another way to convert a raw file, which is to open the picture in the editor. When you do this you’ll see a dialogue which lets you set the profiles for the picture as well as alter the brightness curve. I set the input profile to the one from Nikon. This resulted in a very dark image, presumably because the profile doesn’t include any gamma correction. However by changing the brightness curve to raise the brightness of the darker areas I was able to get these pictures.

As well as the improved quality there are a few other advantages to using the editor to create the jpegs. One is you can make any changes before conversion reducing any loss in quality from compressing multiple times. Also if you’ve added any tags or a rating to the pictures these get carried across when you save the new jpg file. Finally there’s the file size. For some reason jpeg files created with the converter are on average seven times bigger than ones created through the editor.

I’ve ordered an IT8 target, which I’ll be able to use to generate my own profile. Hopefully this will be better matched to my particular camera and will include the gamma correction parameters. I’ll write about my experiences with it when it comes.

Adventures with Raw part 1

When I went to Holmebrook Valley Park I took the pictures in raw mode, as well as jpeg. One of the advantages of using raw is that it’s easier to correct any mistakes you might have made when taking the picture. For the first couple of shots the camera was set to manual mode rather than aperture priority. This meant the exposure was wrong for them.

This is the jpeg image from the camera.

This is the raw image converted into jpeg format. The detail in the clouds has been restored. The only downside is the purple spots at the sides. Those can probably be removed by tweaking the conversion settings. Otherwise it’s easy enough to crop them out.

Now to the downsides. Firstly the files produced are a lot larger. Using the highest quality jpeg I can get over five hundred pictures on a 2GB memory card. Using raw I can get around 150.

Secondly the workflow becomes more complicated. For most uses you’ll need to convert the pictures to another format before you can use them. Also you now have to worry about colour profiles. These store a description of the colour space of a device. jpeg files have the colour profile of the camera embedded in them, but raw files don’t.

You’ll need at least a colour profile for your camera and one for your display. Their should one amongst the software that comes with your camera. The one for display will either be sRGB or adobe RGB. sRGB is better if you’re going to use the picture on line, while Adobe RGB is better if you’re going to print it. Optionally you can use also use the profile for your printer in order to see what the picture will look like when you print it.

Within DigiKam there is two ways to convert raw files into other formats. The easier of the two is using the conversion tool. This can be used on a single image, or a batch. It has options for reconstructing highlights, adjusting the brightness of the image and changing the strength of the different colours.

I used this option to convert the pictures from Holmebrook.

The more complicated way is to open the picture up in the editor. I’ll write more about that later.