Photography, Computer Science and Everything


UC4Chrome – a social network demo

Finally, after months of silence some output from my diploma thesis. UC4Chrome – a social network demo, gives a brief overview about my current work. This video is hosted on the KIT webserver, so you might have to click twice to start it. Enjoy.

UC4Chrome - a social network demo video

UC4Chrome - a social network demo video

Amphi Festival 2011 – Tanzbrunnen Cologne

Amphi 2011 group shot

Amphi 2011 group shot

This weekend Tanzbrunnen Cologne with the Amphi Festival 2011 was the number one gathering place for most (wo)men in black. As promised in the previous post’s comments but heavily delayed are some example shots taken with Socker the sturdy standard reflector. I beg your pardon. The first few pictures in the following gallery are not taken with Socker but you’ll see the difference without any problems. The actual Socker shots were taken with the Nikon SB-800. Hurray, even this model fits the IKEA design 🙂

I have to refine my statement about the quality of light Socker has. The “smooth but defined fall-off on the edges” is only visible up close and personal. Bring some distance into play and it turns into a much tighter and focused spot light. This is not too surprising as the “hardness” of a light depends on its size relative to the subject.

All in all it was a nice and relaxed festival with its ups and downs. For example as I have been told by the panorama guerilla who supplied the opener, this years group shot was an exciting adventure due to heavy security activity. It’s a pity panorama software does not assemble face to face contact across different exposures. If you know a tool or algorithms please drop me a line. I’ll forward it 🙂 Some of my favorites for this year: [(2950, 1424), (3490,1610), (5240, 2200), (4222,1567)]. You’ve been there during Nitzer Ebb? Why not search yourself and tell us about it?


2011-07-22: Due to discussions with friends I came to the conclusion that “there is no bad publicity” so I decided that providing no platform for certain things is the better choice. This section originally containd the following links to articles dealing with Amphi 2011:  [1], [2], [3]


And to join the choir: What’s it with all the rubbish this year?



But enough of that, hope you enjoyed the pictures. Until then, sincerely yours, P.

Building a sturdy standard reflector.

A few days ago while strolling through a local IKEA branch I stumbled across their flower-pot model “SOCKER” (height 16cm). “Standard reflector” was the thing that instantly came to my mind.  Why build a relatively heavy weight standard reflector you might ask? Card-board snoots with black gaffer tape usually do a great job at restricting light and the zoom settings of most modern flashes also work pretty good. My personal reason was that snoots tend to be too restrictive whereas bare flash even on the longest zoom settings can be too wide. It’s also much more professionally looking and longer living than a card-board snoot plus it can be built quickly and cheaply. Maybe in the end the reason I built the reflector is just because I could 🙂

This standard reflector was built with a template for the Nikon SB-600. The SB-80DX might work as well. To use it for larger heads like those of the SB-24/25/26/28 or the SB-900 you will have to use the next larger version of SOCKER I guess. They come in all sizes so you can find one for your strobes head as well.

SOCKER the sturdy standard reflector.

SOCKER the sturdy standard reflector.

Bill of materials

  • IKEA SOCKER 16cm. (1,49€)
  • Dremel or another rotary cutting tool with a cutting wheel.
  • Optionally a rotary grinding stone.
  • 1,5cm tension belt (1,49€)
  • Small patch of black felt. (0.49€ ?)
  • Black and glossy (impact-resistant) spray paint. (7.99€ each)
  • Sandpaper. (0.49€ ?)
  • Superglue. (1.99€ ?)
  • Heat. (ideally an open gas flame)
  • Hot glue, no pistol needed.
  • Adhesive tape and some thin foil.

Code of practice

  • Measure your strobes head and create a template.
  • Transfer the template to the rear end of SOCKER.
  • Cut an H shape with the cutting wheel.
  • Optionally cut into the middle of the line where you want to bend the metal “doors” inside.
  • Cut about 2cm long slots into the sides to be able to mount the tension belt.
  • Place the hot glue behind the metal “doors” and melt it to support them.
  • Remove about 45°-75° of the metal ring on the bottom of the reflector with the cutting wheel to make place for the strobe.
  • Use the grinding stone or the sandpaper to get rid of the sharp edges.
  • Mask the reflector with the tape and foil, then paint it black. Let it dry and spray it with the glossy paint.
  • Glue the felt to the rear area where the ring was cut out to prevent scratches on the strobe where reflector and flash touch.

I hope the documentary pictures in the gallery taken with a smart phone will help illustrating the steps involved. If something is unclear please ask. There is one thing I would like to emphasise on though and that is the use of the hot glue. After cutting the H-shape and bending the metal doors inside you will most likely realize that they are fragile and could break off sooner or later. Cut a cylinder of hot glue which is supposed to go into a hot glue pistol to a useful length and just place it inside the reflector, as seen in the picture. Melt the glue over an open gas flame and it will slowly crawl into place and reenforce the metal doors. Hot glue with a high melting point is an advantage as the strobe can get hot when fired successively. The glue I used did not melt yet and I think I didn’t even come close to melting even under heavy use/heat of the strobe in bright sun on a hot day.

SOCKER at work.

SOCKER at work.

I really really like the quality of light this reflector has. It is focused yet not too restrictive with a smooth but defined fall-off on the edges. My main usage scenario is with a SC-28 attached to my D7k in TTL handheld to the left or right at the length my arm. Combined with a DX normal lens like the 35mm 1.8G or a slight wide-angle this combination is perfect for parties and all other highly mobile situations. You want to make yourself unpopular? Why not use it for some aggressive street photography? Just kidding 🙂 Socker makes a great standard reflector, give it a try, you won’t be disappointed!

SOLVED: The cleaning question.

So you bought a neat little camera body together with two or more interchangeable lenses you played around with it or used it on your assignments and you took really good care of it. BUT: No matter how carefull you are with your equipment the sensors of todays DSLRs is not sealed off from the rest of the world meaning that sooner or later there will but dust and other dirt meeting on it to throw a dirty little high f-stop party. The results can usually be seen above f/8 when shooting an evenly lit bright surface. Dark spots everywhere! Alert!.

The problem: Dirt on you DSLRs sensor.

The problem: Dirt on your DSLRs sensor.

At this point you usually have three options:

  1. Send in your body for maintenance.
  2. Buy an expensive cleaning product.
  3. Get your hands on a perfectly working ultra cheap cleaning product.

While an inspection and a professional cleaning is good idea from time to time you do not want to do this too often. Sending the body to the manufacturer or a local service point usually has 3 or more days of “downtime”. Local non-official stores and dealers can be fast but cost the same from my experience. Another reason to send in your gear the manufacturer is that you are most likely give a certificate of maintenance which everybody loves especially if you plan on reselling you stuff sooner or later. The second option is what every company with a cleaning product and the general XYZ photography magazine advertisement wants you to do. Its the no-brainer solution but not in the positive sense. Holy crap is this stuff expensive. You can easily spend 80€ on some sensor swipe whatever pads and 20ml of stuff called “Eclipse”. That is a lot of money considering that the only thing you want to do ist getting rid of a little dust.

As a third option you can use your brain and think a little. The stuff called Eclipse is 100% pure methanol, the sensor swipes are some kind of soft tissue usually dipped in methanol. You can PERFECTLY clean you DSLRs sensor using Q-Tips and methanol. I tried a lot of stuff and this is by far the cheapest and best solution i have come across, as long as you make sure certain conditions are met:

  • Make sure you really use analysis grade clean laboratory Methanol.
  • Use some tips with 100% cotton.

When searching the net you come across a faction of people who do not think to high of this cleaning method. That usually is because the used the wrong alcohol. Isopropyl alcohol (Isopropanol) which most pharmacies want to sell you here in germany has the disadvantage to leave schlieren/streaks on you sensor because it seems to be more hygroscopic than methanol. Ethanol on the other hand which is the second offer pharmacies will make usually contains denaturants to keep you from consuming it but also leaves schlieren.  I’m no chemist though, i write this drawing from my experience. Methanol evaporates perfectly fine without leaving streaks. The reason you read that you should use the original Q-Tips on most forums is that they are 100% cotton. You can use every other tips as long as it is not made of a synthetic micro fabric that will get attacked by the methanol or has some other smearing “feels good on your skin” additives.

The problem with Methanol though is that its poisonous. Here in germany most pharmacies don’t want to sell it because the can be held responsible if something goes wrong with it. It’s perfectly legal even though Methanol is listed in the Chemikalien-Verbotsverordnung (ChemVerbotsV), a list of dangerous and or poisonous chemicals. Last week i had some really bad experiences with the pharmacies here in Karlsruhe. They tend to treat you like a terrorist and complete idiot when asking for Methanol, it’s a shame. You’d imagine that you are treated as a mature and responsible citizen but that is not the case. Five pharmacies later and i gave up. Luckily a friend who happens to be a chemical laboratory worker got me a small bottle. He also confirmed that it’s not dangerous at all as long as you do not drink it, use it to poison someone else and make sure that there is a basic ventilation like a window which perfectly suffices.

My advice: Save your money, get your hands on some Methanol and some cotton tips. You’ll be surprised how perfectly this works. It also removes heavier contamination. I once sneezed on my sensor, Methanol saved my day! Cost for the complete cleaning system: Depending on where you buy it 4€ tops!

The solution: Methanol and 100% cotton tips.

The solution: Methanol and 100% cotton tips.

If you find this useful, why not drop me a few coins? thx 16NMkuom1qxFSrBytPbmVfBvkMJ6GGm29X

Nitro R/Cs

What is small, fast and stinks like hell? Right, nitro powered R/C cars. These little bastards are fast, dirty and 100% pure fun, except that there is the tendency of modding and repairing them 75% of the time instead of actually racing around, even on location and in a group with others. Last week I twice had the chance to meet with a group of ongoing R/C car junkies. The just bought their gear so there was nothing special or self constructed to see yet but that on the other hand gave me the chance to experience and share the same novice perspective on the topic -> “WTF is wrong with this car. Breaks? Maybe pull the starter a little faster? Maybe its the Ignition? Ups… no fuel!”. One can get a full starters kit for about 150 EUR with a fully assembled R/C car, the actual remote control and a few replacement parts, nitro excluded.  There is one thing i do miss though and that is my beloved green and red turtle shells… you can’t have everything. The starters set almost got me hooked but reflecting on it I luckily came to the conclusion that I have more than enough expensive hobbies and money sinks.

R/C Nitro car

R/C Nitro car

R/C cars are a great way to test you cameras auto focus. To paraphrase Ken Rockwell, the D7000 3D continuous AF grabs on to your target like a pit bull and doesn’t let go until you say so. Combined with the amazingly fast AF capabilities of the Nikkor 70-200 2.8 VR2 the cars had no chance of escaping. I’m still stunned by the amazing performance of this body lens combination, the out of focus miss ratio was only about 10% of the shots even though the cars were constantly moving back and fort, from left to right and i have little “sports” shooting experience what so ever. The shots on the off road track were taken using a Hoya ND 8x neutral density filter, the body glas combination mentioned above, a SB-900 with a 24′ softbox and two bare SB-28s all triggered using my modified Cactus V2s. The ND filter was used to push down the ambient light which was bright sun from time to time due to partially cloudy weather.

Now why do you want to take away light you might ask? First of all shooting in bright daylight forces you to stop down to maybe f/5.6 ISO 100 or worse to  stay within your strobes speed limits… bye-bye shallow depth of field. Second the strobes wireless triggers also can’t shoot any faster than 1/250th of a second which is the fastest sync speed you can reach using a Cactus V2s and most other wireless triggering systems. Yes you are right, i wrote 1/200th of a second in the Fontainebleau post, but that they can reach a 1/250th with fresh batteries, my mistake. Shooting faster than 1/250th your shutter curtain will crawl into the frame. By using the ND you make your glass worse w.r.t. speed but without affecting the DOF. This will put more pressure on the strobes as they are affected by the ND as well and have to compensate for it by emitting more light. On the other hand you can shoot a 1/250th f/2.8 without the ambient burning into your picture and still use strobes. Using a high-speed sync system like Nikon’s CLS can help here as well.

Having read this months “CT Special Digital Photography” (german version, the english translation is not yet available) article on sharpening I had to try RawTherapee‘s RL deconvolution sharpening implementation. There are a lot of open source raw converters and tools but I think RawTherapee is by far the best converter when it comes to a productive and time effectiveness in the workflow. If you haven’t tested it yet you should definitely give it a try, you won’t be disappointed. The RL deconvolution uses an imaging systems so-called point spread function (PSF) to iteratively calculate a the “original” image.

The basic idea is as follows: If a perfectly 1 pixel sized beam of light hit my camera sensor after being transmitted by the glas it would most likely still blur due to the systems inherent imperfections. Even if we do not know how exactly this perfectly small beam of light is blurred we can estimate the blur which most likely is some kind of radial pattern. This pattern is the PSF. With this estimation of the blurring we iteratively calculate the “original” image for every pixel of the picture. The RawTherapee implementation took much more time on my system than the USM but for single images or large-scale printing purposes i see some clear advantages over USM. The following image was processed from raw and scaled to 200% without interpolation. You need to view it as a 100% image in your browser to see all details and differences.

None - USM - RL Decon comparison

Left to right: None - USM - RL Decon

Crashpad junk?

Directly after the seduction of Fontainebleau i decided the to go get my own crashpad. Some might call it shopping but i prefer to think of it as an investment into my well-being. The decision and preceding web research phase wasn’t easy but being an employee of THE local outdoor store and benefiting from a few companies discount programs i finally came to terms with the Black Diamond Impact Pad. It’s a simple pad without any unnecessary features or as the advertisement puts it: “The Impact is a minimalist, all-around and entry-level pad.”

Black Diamond Impact Crashpad

Black Diamond Impact crashpad.

The Pros

  • Good cost-performance ratio. (Amazing if you can get the BD employee discount 🙂
  • Small, doesn’t eat much storage space.
  • Unfolds perfectly flat, unlike the BD Dropzone, it’s brother model.
  • Folds perfectly flat, with right angles, unlike the Dropzone.
  • Unverified (but fully trusted source): Very durable and long living foams.
  • Two handles, you can carry it like a carrying case without having to close the clips and it doesn’t unfold.

The Cons

  • Small, 100 x 114 x 10cm.
  • Straight fold, you might accidentally kick through. There are other models that have an angular fold or even a continuous surface.
  • Polyester fabric. Other models feature nylon/polyamide fabric, e.g. Cordura which is very durable and well-known from heavily burdened working and protective clothing.
  • Slippery on the outside. The Dropzone features a sticky rubber outside which might reduce shifting on impact. Today i had some unpleasent first hand experiences with shifting so this feature is weighted much heavier now, at least for myself.
Black Diamond Impact Crashpad

Black Diamond Impact Crashpad

The pictures were taken with a very basic setup. As you can see they were shot white in white with two shoot through umbrellas and spill floating all around the place due to the walls and ceiling. Usually you want to avoid or at least control you light spill but with a narrow environment and a white in white subject it comes in handy. Basically all you have to do is watch your levels, mainly the blacks and then just drown the whole setup in light. Here is the data on the shots, double SB-28 1/2, 28mm left and 35mm right, ISO 100 f/5.6 1/160th and distances of about 1.5 m / 5 ft. Free-form your subject, add in a drop shadow and you’ve got an instant ebay picture. That is of course if your subject isn’t covered in dirt and footprints all over it’s fabrics like mine.

For a catalogue shot on the other hand i think these two wouldn’t qualify. First of all your subject _has_ to be perfectly clean and second the arrangement is far from optimal (e.g. placement of the laces). This is where are tripod does an amazing job, given that you want to spend more time on composing 🙂 I don’t exactly recall where i read it, it must have been on more than one source but it’s such a mind blowing insight that i have to repeat it once more. When you ask photographers what a tripod is good for many will tell you that it reduces camera shake and blur, but this is only half the truth. The main benefit of a tripod, and i absolutely agree on this, is that is helps you composing your image. It reduces the load on your mental CPU, e.g. physical movement of your body while standing in a slightly crouched, uncomfortable position to get the angles right, holding your breath or exhaling before pressing the shutter  and so on… It allows you to focus on the much more important part of overall image composing.

But coming back to ebay, don’t think anyone will appreciate your efforts.  You could as well just take the manufacturers pictures which of course can get you into trouble, even as a privately selling person (at least in Germany). “Original” pictures by the manufacturer just like all other pictures do have copyrights and usually this means that they are supposed to be used by authorized dealers only.

Crashpad shooting setup.

Crashpad shooting setup.

To sum things up the Impact is a neat little pad and not junk at all.

Bienvenue à Fontainebleau

Finally, after hours of retouching i’m somewhat close to being satisfied with the selection and post-production of most of the shots taken in Fontainebleau, France. The main pictures can be found in my flickr stream, or in the linked gallery at the right bottom of this blog. But first of all: i will never ever curse the german radio again! You might think that it’s repetitive and boring but that’s only until you drive through the french countryside. Here you have to discover that having no CDs in your car is as funny as half a day in purgatory, only with chanson. We stayed at Grez-sur-Loing which is located about 10km south of Fontainebleau. The town’s best know  landmark is without question the Tour de Ganne, here seen in a slightly tonemapped nightshot (5x time exp, +2 EV stepping).

"Tour de Ganne" à Grez-sur-Loing, France

"Tour de Ganne" à Grez-sur-Loing, France

The local camping site seems well organised, it has reasonable prices, everything is clean, there is a bakery about 10 minutes away and they have WiFi 🙂 Anyway, we did not drive there just to hang around the camping site. Having built up our base we packed our stuff and went to work. Let me tell you one thing, Fontainebleau is the undisputed bouldering heaven. To paraphrase a co-worker: “You made the mistake to go to Fontainebleau. No you will compare other areas to Bleau for the rest of your life.” But see for yourselves, here are two slight impressions:

Strolling around.

Blocks in the wood.

Strolling around. Deux.

More blocks in the wood 🙂

Unfortunately due to the unforgiving laws of physics and gravity in particular the whole trip had to be shot without a polarizer. Three days prior to our departure it fell and cracked… Even though i ordered a replacement immediately after this devastating 80€ incident it didn’t arrive in time, thx to DHL. It would have been the perfect situation to further explore it’s effects but i just had to get along without it.

All in all the whole trip was a refreshing alternation to my common studio photography workflow as i relied much more on available light and reflectors than on speedlights. They are far less work and tend to blend in more smoothly which of course isn’t that surprising. My personal highlight of the trip is the mixed light shot of Dirk pulling up easily. As usual in bright sun situations like these flashes are competing with the available light, dictating the maximum synchronization speed. The new Nikon D7000 can sync up to 1/320th of a second but using modified Cactus V2s triggers the picture had to be shot with a maximum speed of 1/200th or otherwise the curtain would have creeped into the frame. Maybe fresh batteries would have helped reaching the de-facto standard of a 1/250th well known from other camera/trigger combinations. David Hobby did an article on this a few weeks ago, i heavily recommend it as this article and its archived logical predecessors highlight and illustrate this “sync limit” topic nicely. You might want to use his search to look them up. As a result of the 1/200th Dirks face is a little more blurry as the AL burns in more heavily at this sync speed. In addition to the AL the reflector placed to the left which was supposed to fill in some of the shadows added to this effect and should have been taken out in hindsight.

Hope you enjoyed my first full article on this blog. Depending on my spare time there might be some more coverage of Fontainebleau. Thanks for reading, P.