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Since the impending sunset of Google Plus I'm contemplating where to move with my online presence. Google Plus has served me well as a newsfeed and micro-blogging site and also a good way for staying in touch with like-minded people. I've backed up all my posts and temporarily moved them over to blogger, but that one might turn out the next candidate for demolition once Google finally gets bored with it.

So I'm building my own presence here.

Let's see how it turns out.


It may sound strange to some. After all, digiKam is for digital cameras, it says so in its very name. However, nowadays all photographs eventually end up in a digital format, and so I tend to think of photographic film as a form of light sensor with certain, quite favorable qualities. This article, split into two installments, deals with film photography in a digital world, and a tool I wrote to support its use. This first part is about the why. The second part will demonstrate the tool and explain how to use it.

How it all started

A couple of weeks ago I started working on a new tool for the digiKam photo management application. My newly discovered love for shooting 35mm film culminated in buying a Canon EOS-3 SLR and a scanner and I have spent a lot of time trying to get good results from scanning the color negatives directly. It's a problematic process, to say the least.

One of the my reasons for shooting film is how it presents color on the final paper prints, but it's tough to recreate that if you don't scan from prints (it's expensive) but from the developed negative. Getting rid of the orange mask is a trivial challenge, but going from there to a pleasantly looking image on a computer LCD is not. How to develop the films "signature color" without non-reproducible manual intervention?
I started with VueScan which presents itself to be well set for color negative scanning. It got some good, initial results for easy images, but its internal automation is too easily thrown off path. Photos of blue sky? Forget it, the automatic correction creates a muddy gray or mauve but no blue. Also, the amount of film profiles is very limited, for example there are only few Kodak films and none of them are recent. No "New Portra" 160 or 400, no Ektar 100. And yes, you need those profiles to go from a raw, linear scan to something that looks like an photo. Another thing about VueScan is that I don't know what it does and I keep asking myself, is this really how Kodak Gold should look? This ultimately leads to the question of how to recreate the color "signature" of a certain film instead of just getting an "image with nice colors".

Searching for inspiration

When googling for what others do one finds a lot of descriptions of "best settings" for Silverfast or VueScan but nothing that you could devise a script detailing the steps one would need to perform in order to go from Negative to final Image with basic image manipulation tools. Still Google spit out an inspiring article from fellow blogger Obakesan, a Negative-scanning tutorial providing basic input on how to perform most of the necessary steps with the simple level adjustment tool found in any image manipulation software. That article was what eventually culminated in the tool I have written and that just got released together with version 2.6.0 of digiKam, and which I christened, unceremoniously, "Color Negative Inverter", for this is what it does.

The tutorial had a lot of steps to perform manually and didn't fulfill my requirement for reproducibility of images, like hand-adjusting the levels and then manually correcting the colors. You get a photo that looks good as a result but your wife will tell you that her dress had a totally different color that day. Trying to achieve that I went looking for characteristics of film from which I could compute the necessary settings.

How color film works

Chemical film in any format comprises of a plastic carrier film that is coated with light sensitive material. Color negative film for the standard C41 process has three such layers which are sensitive to red, green and blue light and then form a cyan, magenta and yellow color dye. The more light of a specific wavelength hits the film, the higher the density of the resulting color dye. The relation between wavelength, illumination and density is known and published by the film manufacturers in data sheets, like this:
Looking at these one finds that the dye densities for cyan, magenta and yellow map a relatively small density range to a quite large illumination range, and that density range decreases drastically from cyan to magenta to yellow. This mapping has to be translated into parameters for a computer algorithm.

How the Color Negative tool works

First of all, the input data is a linear, raw scan of the film negative, with no corrections like white balance, gamma or tone curve applied. Also, it should be a well exposed scan, using the full dynamic range of the scanner, without clipping of any color channel to null or full scale. Each channel should be represented with 16 bit. The color profile of the scanner output should be known. Your scan program must be able to provide this. I know no free Linux scan program doing that, so I bought VueScan by Hamrick Software. The histogram of such a scan will look like this:
As one can see, the red color channel occupies the widest range while blue has the smallest range. The brightest values of each channel together represent the color of the orange mask. If you adjusted the levels so that the maximum input of each channel matched these values, the orange mask would turn into bright white. This is what the Color Negative tool does to remove the mask.
To map the input range for each channel, one also needs to compute the minimum input. For this task the density profile of the film is used. For Kodak Gold 200, the maximum density just before the shoulder (around the 0.0 point of the exposure axis in the above diagram) is (1.53, 2.00, 2.40) for R, G and B, on a log10 scale. Since we're still talking about a negative image, the maximum density is equal to the minimum brightness. You just need to transform the logarithmic density from the diagram into a linear value. Then apply a gamma correction (globally and to each channel to balance the colors) and you're pretty much there, you just need to invert the image. 
This is as far as the Color Negative tool will take it. From there it's a bit like working with RAW files from a digital camera: You may need to fix the levels and adjust the white balance and tone curve, or use any of the digiKam tools to tweak the photo until it suits your taste.

Collecting film profiles and samples

As best results are achieved with matching profiles for each film, I had to collect data sheets. Not many companies nowadays make C41 film and most of them are by either Fuji or Kodak. I tried finding as many recent and not so recent or even discontinued film data sheets as Google would find. I actually tried verifying the profiles by shooting a roll of each to see how it goes, but some are hard to find today. I think I achieved a good coverage but for some brands like DM Paradies that are re-branded Kodak or Fuji film stock no data sheets exist. For example, some say DM Paradies is Kodak Gold, but looking at the scans I somehow doubt that. If you find data for obscure brands my tool doesn't support yet, I'd be happy to hear about it. Just send me the PDF containing a density diagram like I've shown above. You can additionally send scans to verify the result, just make sure they are linear uncorrected scans with 16 bit per channel. They should also have a bit of the orange mask color around the actual photo. Even better, send me a roll of the film 🙂

What next?

The basic functionality of the tool is complete, but I would like to add a few features and of course more profiles. One feature will be automatic detection of orange mask values, which is pretty easy to do. For now there is only a color picker so you need to perform a few clicks manually, but fortunately you only need this once for every roll of film, if your scanner has consistent output from picture to picture within a roll. The automatic white point calculation for the negative only requires a bit of searching in the histogram bins and therefore will be easy to do. Suggestions for improving the user interface and also the quality of the conversion? I would certainly like to hear your suggestions.


You may know that the nationalists party in Sweden just managed to enter parliament for the first time. The reaction of the Stockholm people is quick and concise: they're all out on the streets protesting against racism. I found this photo on flickr, my contact Sean was out on the street with his camera and managed to take this fantastic photo! It's marvelous, the way it captures the moment is brilliant. Go and visit his photo stream, there are many more from the "No to SD" demonstration, and say NO to Racism, wherever you can!

Tour Eiffel
Originally uploaded by thinkfat

On Sunday evening Eva and I returned from a long weekend in Paris. We went there with our friends Andrea and Sergio to spend some time in Paris for leisure and to take photos, of course. Sergio and I also went on a night tour with a photo guide, Gilles, who showed us around and gave tips for nice motives in the City of Lights.

I will be posting some photos on my flickr account during the next days.

Originally uploaded by thinkfat

I like carnival parades! There's no other opportunity to take photos of smiling people, enjoying themselves, in colorful costumes, actually wanting to be seen.

This was my second year joining the crowd in Mayence during the Carnival Monday parade. I love to go there. It is a relaxed and joyful atmosphere and you can get really close to the people, interacting with them. The security is minimal, everybody is just having fun and does not mind a photographer running across the street, diving into the parade, taking images like crazy.

I used only the 45-200 zoom and it did not disappoint. It's fast to focus, light and sharp and the OIS really helps. I filled three memory cards with almost 1000 photos. The set on flickr contains approximately 120 images which I liked most. Many of them are Jpegs right out of the camera, just resized for presentation, some I had to lay hands on, some were developed from RAW.

Come, see and enjoy!

In a previous post I ranted against a local "Subways" shop as a prime example for bad food in Darmstadt. I want to share an example for good food today.

Asian restaurants are often laden with kitschy decoration and the menu is mainstreamed to comfort the local taste. Also you have the same dishes with only small variations everywhere. Traditional style cooking is rarely found anywhere.

A very nice example of stylish interior and excellent cooking is the "Ngoc Lan", small Vietnamese restaurant located a bit outside the city centre. You find it at the corner of Bismarkstraße and Steubenplatz, see the map embedded below.

Größere Kartenansicht

We come here once every while and the quality of the food is always great. The cooking is very traditional compared to the standard issue Asia Kim or Dong Dong in more prominent areas of the town. Well cooked, spicy and with fresh herbs, the menu lists many unique meals very different from the usual "fried noodles with chicken/pork/beef". A selection of well mixed, fruity Cocktails can be had as well.

The single room is bright and nicely decorated, calm in minimalist way but not frugal. Go there after dark to experience the full effect of the lighting. There is parking space behind the restaurant, about 15 places in the lot. No need to make a reservation, in fact we never found more than a couple of tables occupied whenever we came there. Which is a pity, because it means it won't stay open for much longer. So go there and enjoy before the place closes for good.

Apart from the obvious Pun, this is what unfortunately happened to me a few days ago. I was buying some snack before entering the train back home at Paris Gare de l'Est and was probably spotted tucking my wallet away. I put it in an outside jacket pocket, a circumstance that immediately retaliated itself as I stood waiting by the platform for my colleagues to arrive.

I was approached by an Asian looking women of middle age and asked for the train to Basel. It struck me odd to be asked for this for my obviously tourist look (after all I was carrying a backpack and a camera bag) but not odd enough to raise my suspicion. While talking to the woman, which took a good amount of time I felt something brush my backpack but again it did not alarm me enough to make me look around. I think I was set up with a classic distraction manoeuvre to give the thief opportunity to pick the wallet from my pocket. It can not have taken him/her more than a couple of seconds despite the pocket being zipped shut.

I did not notice the loss before the conductor asked for my ticket, a good while after the train left the station. I was baffled, but quickly recovered and phoned the emergency hotline of my bank to have the banking and credit cards suspended, avoiding additional financial losses apart from some cash that was in my wallet.

Still, I've now lost my ID, drivers license, credit and banking cards and a couple of other documents that can all be replaced, still there is a significant amount of time and money to be spent now to have them all back. Definitely gives you a sour taste being ripped off like this.

What to learn from this? Crowded places should keep you alert. Strangers approaching you should make you look around for other strangers standing close. Wallets should not be kept in outward pockets. Documents should be kept apart from the money to limit the damage and the amount of time to spend recovering from the loss.


Look what the cat just brought in. Holy cow. Only miscreants and evil-doers fear Google tapping their into their privacy, but the Righteous have nothing to worry about. And it's all the governments fault, anyway.

But this doesn't come as a surprise, does it? Google is an information broker so how can they share anyones concern about information not being another good to sell. However, it's primarily information about people that they collect to drive their advertisement business. This is hardly neutral goods.

I'm wondering if with all this business background Google can still be the best resource when it comes to Internet research. Either the web complexity has grown to a point where they cannot come up with good search results any more or they weigh the results too much towards what their customers think you should be seeing, anyway I found it's becoming increasingly difficult to have good search results with Google. Too many hits are on proxy sites that just pretend to have the keywords you look for and instead reflect to some shady online shops claiming to sell "cold fusion energy cheap"?

I only recently found time to process and upload some photos I took during our summer holiday this year. Instead of going abroad we decided to travel Germany, there are quite a few places we've never been. This year we went East, visiting Thuringia and Saxony. I've uploaded a selection to Flickr, with more to come. Enjoy today some impressions collected visiting Dresden, which marked the end point of our journey.

In a recent interview with the Digital Photography Review web magazine a Nokia representative talks about convergence devices like the N86 mobile phone incorporating an 8MP digital still camera and aiming to replace digital compact cameras in many peoples' pockets. Read the story here.

Seemingly unrelated, The Register has an article about a provider in the United Arab Emirates pushing a trojan horse program as a software update to their customers Blackberry smart phones. The sting was only accidentally discovered and if anything can be learned from that, it is that stuff like that is not just overheated imagination of a few conspiracy theorists but happening right now under our very eyes.

This got me thinking. Do I really want all those features crammed into a connected device I have no control over? Each and every feature requires me to provide more, sensitive information. Phone books are no longer just phone books but store email and postal addresses of my contacts. browsers store web site credentials, Ebay, not to mention PayPal accounts. All my data under the reign of a software that can be changed at any time, without me even noticing.

I may want my camera be a camera, and my mobile phone be just that and nothing else.