Further fisheye fun

Yesterday I visited Longshaw estate. I will be writing about the visit later but while I was there I took some more pictures using it.

Here is an image of the main road taken with the camera. The distortion is clear from the way the road curves in the image.

When editing an image in DigiKam, under the enhance menu there is a lens correction option. This allows you to correct barrel distortion (lines bend inwards) or pin cushioning (lines bend outwards). Using it is a matter of trial and error. This is made harder by the fact it takes several seconds to update the preview every time you change a value.

After using the correction tool the outer edges showed a lot of curvature outwards, so it was necessary to crop the image slightly to remove that.

This is the result. the distortion hasn’t been completely removed, there’s still a kink in the road.

This is another image of a set of trees.

Origional image:

The corrected image:

For comparison here is the image taken using a regular 10mm lens:

Even though the corrected image had to be cropped, it still has a wider field of view than the one from the 10mm lens.

Clicking on the images will take you to a larger version.

NB: I mentioned the gallery feature in the last post. Unfortunately I wasn’t able to get the image uploader to work. It kept causing Firefox to crash while compressing the images.

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.

DigiKam

DigiKam is a photo management program that is being developed as part of the K Desktop Environment for Linux systems (hence the strange spelling/capitalisation. When KDE was first started the K stood for Kewl but now it just stands for K).

However there is good news for Windows users. Recently the license of one of the libraries used by DigiKam has been changed which has made it possible for a Windows version to be produced. A Windows port of DigiKam is being worked on, along with other KDE applications.

In DigiKam pictures are stored in a tree of albums, with each album corresponding to a folder on the hard drive. I tried a number of schemes for arranging the pictures before deciding it was simplest to just arrange them by date.

Each picture can be given a number of tags to help organise them, similar to Flickr. They can also be given a rating from 0 to 5.

The central section shows thumbnails of the current pictures.

The column on the left lets you select the album, date or tags to show.

The column on the right lets you filter the pictures shown or view the details of a particular picture.

When you click on an thumbnail it brings up a larger view of that picture. It’s possible to view the full size picture or expand it to fill the screen. You can move back and forth between the pictures or changes the details of an image from here.

It also has an editor mode. From here it is possible to crop, rotate or resize and image as well as applying various effects. There are also options for repairing various problems.

It is able to handle Raw files using the dcraw program by Dave Coffin.

So far this is like most similar programs. However it has a feature that I haven’t seen in any other program. A light table.

While viewing the pictures in the main view you can select to add them to the light table. The pictures are shown as a string of thumbnails at the top of the screen. You can select two of them to see larger versions of below. Nowadays when I go out taking pictures I end up with a lot of similar pictures. Being able to view them side by side makes it a lot easier to choose which ones to keep.

In all I find that it makes the process of sorting, processing and cataloguing my pictures a lot simpler than it would be otherwise. So when it does become available on other platforms I’d recommend trying it out. If it doesn’t suit you, you can always ask for your money back.

You can find out more about it at its website