Stephan Paukner :: syslog - Photography

A peek on current DSLR tech, II

paux@paukner.cc (Stephan Paukner) — Wed, 01 Sep 2010 20:52:00 +0200

Apparently, it’s time for my yearly follow-up on Canon’s releases.

Canon announced the EOS 60D. It’s interesting that their prosumer “x0D” line now got downgraded in a certain sense: This DSLR became more similar to a cheaper bridge camera, with a vari-angle LCD, less weight, plastic housing, fewer fps and SD cards instead of CF. This is probably a measure for increasing the difference to their EOS 7D, which should attract the more dedicated amateur.

However, there won’t be a 7D or 5D Mk II in my hands at all. My 40D is just working fine for me; unfortunately, I hardly found time to hold dedicated photography sessions apart from the obvious ones with my child. There’s still a lot of potential with and within my camera, although the maximum (unboosted) ISO of only 1600 is rather limiting sometimes, given that one could have ISO 6400 with current models.

And the limited number of occasions I mentioned is also a reason why there was no “lens p0rn” in my blog recently. Although I had predicted the purchase of a tele lens for fall 2008 and then for the end of 2009, I didn’t buy one, as I rarely missed such a tool. However, there seems to be the ultimate candidate for me to finally put one into my bag at the end of 2010: Canon’s newly introduced EF 70-300mm f/4-5.6 L(!) IS USM. It’s rather compact and doesn’t possess the disputed design of their aging 100-400mm. It appears to me as a 70-200mm f/4 “with the 1.4× extender included” in some sense. It’ll be available by October for 1,400. Let’s see if that’ll be my Xmas present for me, or if I rather go for a completely different gadget (namely an Android tablet).

Work around the image scaling "bug"

paux@paukner.cc (Stephan Paukner) — Thu, 25 Feb 2010 20:45:00 +0100

Eric Brasseur explained a “bug” in the scaling algorithm of current image processing software. It’s not really a bug, technically, or mathematically. Calculating the numerical average of the surroundings of a pixel as the new color value is a pretty correct approach to scale an image downif it’s seen as a data matrix. Rather, it’s visually not the thing you’d expect.

Technically speaking, the problem is that the computations are performed as if the scale of brightnesses was linear while in fact it is an exponential scale. In mathematical terms: a gamma of 1.0 is assumed while it is 2.2.

Here’s an example of what might occur:

The wrong way:

Take this image as a start:
Simply scale it down to 50%:

Obviously, this might not be what you intended.

The right way:

Continue reading "Work around the image scaling "bug""

Cheap time lapses with gphoto2

paux@paukner.cc (Stephan Paukner) — Sat, 28 Nov 2009 21:39:00 +0100

“Cheap” should mean here that you don’t need to spend money on extra hardware like a remote timer or on extra software like Windoze (which Canon’s EOS Utility depends on). With a GNU/Linux system, just install gphoto2in Debian, take version 2.4.5 from ‘squeeze’. After attaching your e.g. Canon EOS camera via USB, you can issue the command

$ gphoto2 --auto-detect --force-overwrite --capture-image-and-download --frames 360 --interval 10

to automatically shoot and download images for a time lapse, in this example every 10 seconds for one hour. You should keep all exposure values constant and switch to a lower resolution in advance. You can render an HD video e.g. with

$ mencoder mf://*jpg -ovc lavc -lavcopts vcodec=mpeg4:mbd=1:vbitrate=7200 -mf fps=25 -o timelapse.avi

If you make it bad, it might look boring like my very first try:

If you make it good, it should look like this.

My hope is that I can use gphoto2 with an Android smartphone.

Light gain with fast lenses

paux@paukner.cc (Stephan Paukner) — Fri, 04 Sep 2009 23:23:00 +0200

I was interested what difference there is between the Canon EF 50mm f/1.2, f/1.4 and the f/1.8 model regarding the light gain compared to an f/2.8 lens. The amount of light that travels through an optical system is usually given by f-numbers, the relation between focal length and aperture diameter. Doubling or halving the diameter of the aperture results in quadrupling/quartering the aperture area and thus the amount of light that can fall through:

Practically it is of interest what f-numbers result in doubling/halving the amount of light,

what is thus given by an aperture diameter change factor of √2 ≈ 1.41. Continuously doubling/halving the light amount results in the diameter changing with the factors (√2)^k, yielding the classical sequence

1.4 → 2.0 → 2.8 → 4.0 → 5.6 → 8.0 → ...

The switch from a lens with maximum f/2.8 to one with f/1.4 thus yields 4× as much light, allowing ¼ of the original exposure time. Between f/2.8 and f/2.0 there’s a factor of 2. So, switching f/2.8 to f/1.8 must gain light with a factor between 2 and 4. What’s the exact amount? It’s

So it’s even less than 2.5, while with an f/1.4 lens it’s a factor of 4! Thus, there’s quite a difference in the light amount between those two lenses. And what about the step from f/2.8 to f/1.2? The gain factor is calculated similarly: 5.44. The step from f/1.4 to f/1.2 only yields 1.36× more light.

A peek on current DSLR tech

paux@paukner.cc (Stephan Paukner) — Tue, 01 Sep 2009 21:20:00 +0200

The longer I own my DSLR, the less important it becomes, and the more important it is to focus on the pictures rather than the gear. However, Canon’s annual DSLR presentation was due, and so I had a peek on their new release: The EOS 7D, placed between the prosumer x0D-line (10D and up) and the professional 5D. What’s technically interesting me are

8 fps continuous shooting with a burst of 126 JPEGs or 15 RAWs
19-point AF with new modes
Viewfinder with 1.0× magnification, 100% coverage and LCD overlay
iFCL metering system that respects color
HD-movie mode
Dual 14-bit DIGIC 4 processing

It’s probably targeted against (the successor of) Nikon’s D300 that’s placed between their D90 and D700. While the D90 could be compared to the Canon 50D and the D700 to the Canon 5D, Canon lacked something in between so far.

The current hype to include a movie mode into DSLRs isn’t quite comprehensible to me. Maybe time will show whether video photography will become a style of its own. It appears to me that video capability and operability are rather limited, although the ability to choose between lenses is a big advantage. I’ll rather go for a dedicated camcorder nonetheless.

Regarding the pictures: While it’s still okay for me to be involved in casual techie debates (e.g. about astro photography), they become less interesting when it’s just about cameras. Only the output matters, so I don’t feel an urge to follow current developments in that detail. Unfortunately, I didn’t find the time to go out shooting as much as I had wished, due to priority reasons. However, my next main genre will apparently be child photography in great profusion.

While I’m at it, I was struggling a lot what tele lens I’d finally buy, thinking of getting things closer “out there”. Although Canon’s EF 100-400mm f/4.5-5.6 [review] has a disputed design and is more than 10 years old, Sigma’s recently introduced 120-400mm and 150-500mm lenses can’t outperform it. So it’ll probably join my gear in a few months. I also had tested Zeiss’ ZE Planar T* 50mm f/1.4, but I’m not sure whether I’d use such a lens often. Maybe Canon’s cheap EF 50mm f/1.8 II might be an option.

Finding dark places in Austria

paux@paukner.cc (Stephan Paukner) — Fri, 12 Sep 2008 13:59:00 +0200

Recently I took my first star trail images with my DSLR. There finally was no moon and clear sky, so I took my photo backpack and my tripod with me and drove at 2.00am a few kilometers outside the small town where we were staying that weekend. It was located in the Waldviertel (“Woodquarter”), a rather sparsely populated region at the north of Austria, and so I expected best conditions for taking pictures of a starry night. Indeed, the Milky Way was clearly visible. I pointed my camera northwards to capture the sky rotation, and although it was really dark, I was a little surprised that the trees silhouetted against the sky. And a long time exposure unveiled a faint orange glow at the horizon, although the next populated spot in that direction was a small village a few kilometers away.

This finally raised the question to me: How should I find the sparsest populated place within a certain radius? What data would I need to find that out? A set of coordinates of towns plus their number of inhabitants? Use that to compute an image and blur it? Or rather, is it possible to use data collected in the course of the light pollution issue?

By some research I was finally able to find

the darkest place near the Waldviertel and
the darkest place in Austria.

Continue reading "Finding dark places in Austria"

Canon EOS 50D announced

paux@paukner.cc (Stephan Paukner) — Tue, 26 Aug 2008 20:28:00 +0200

I was really surprised when I read that Canon itself leaked a webpage describing an EOS 50D! The surprise was due to the usual timespan of 1½ years after which Canon presented a successor of their respective EOS line. As the EOS 40D was presented in fall 2007, I didn’t expect a 50D to come before spring 2009. But probably the 50D came a little earlier to be placed against Nikon’s D300 that really outperforms the 40D.

Having a brief look at the specs I have the impression that it’s rather a minor advance compared to the 40D, fortifying the impression of a pure marketing decision rather than a real technology jump. The significant changes in my eyes are

15 MP compared to 10 MP,
DIGIC IV processor compared to DIGIC III, and
ISO 12800 max. compared to ISO 3200.

In the end only the last one in that list could be of interest if it implies a lower noise behavior at the same ISO speed. The jump from 30D to 40D was much more significant in my eyes, while that from 20D to 30D was only a cosmetic one in a similar way. However, as there obviously won’t be another successor in spring 2009, I can now be sure that my EOS 40D will stay a top camera for at least another year.

Much more interesting in my eyes is the upcoming EOS 5D Mk II, Canon’s updated “cheap” FF DSLR. Nikon aimed their D700a FF DSLR as wellat the same target audience. It’s interesting also that Nikon now has two FF DSLRs on the market, both from this year, while Canon announced their first FF DSLR, the EOS-1Ds, already in 2002.

Digitale Bilder organisieren

paux@paukner.cc (Stephan Paukner) — Thu, 14 Aug 2008 20:46:00 +0200

Obwohl ich schon einmal hier laut darüber nachgedacht habe, wie ich meine (digitalen) Fotos organisieren soll, reagiere ich nun auf eine Blogparade zu diesem Thema, auch um mich selbst etwas mehr zur Fotografie anzuspornen.

Auf wie vielen Datenträgern speicherst Du Deine Fotos?
Auf drei bis vieren: Eventuell parke ich sie nämlich schon unterwegs auf dem Datentank. Danach habe ich eine Drei-Zeiträume-Strategie: Solange Platz ist, sind die aktuelleren Fotos am Notebook, zur Bearbeitung und zum schnellen Zugriff. Dann werden alle Fotos gemeinsam mit weiteren persönlichen Daten auf einen Backup-PC synchronisiert, der aber wohl bald durch ein USB- oder FireWire-Festplattenarray ersetzt wird; dort sollen sich alle bisher gemachten Fotos befinden. Zuletzt landen die Fotos zur Katastrophenvorbeugung auf DVD-RAMs (nicht CDs und nicht DVD-R(W)s), da diese relativ lange physikalisch haltbar sind; diese werden außer Haus gelagert. Darüber hinaus werden die besten Bilder schlicht ausgearbeitet.
Wie regelmäßig machst du Backups?
Neue Fotos werden sofort aufs Backupmedium synchronisiert. Monatlich kommen sie auf DVD-RAM. Sobald eine DVD-RAM voll ist, verlässt sie das Haus.
In welchem Format speicherst du deine Fotos?
In dem, in dem sie aus der Kamera kommen, d.h. RAW oder JPEG. Bearbeitungen werden immer als separate JPEGs gespeichert; TIFFs habe ich bisher noch nicht benötigt. Nicht überzeugende Fotos werden sowieso gnadenlos gelöscht.
Welche Ordnerstrukturen oder Dateinamen verwendest Du?
Bisher lege ich die Ordner einfach in der Form YYYY/MM/DD_Thema an, die Dateinamen bleiben die aus der Kamera. Ableitungen erhalten ein Suffix.
Wie indizierst Du Deine Fotos?
Mit digiKam. Allerdings fühle ich in letzter Zeit keinen Bedarf dafür.
Welche Software setzt du ein?
Ich bin sehr hart im Nehmen, setze nämlich zu 100% Linux-Software ein. digiKam verwende ich zum Taggen und Aussortieren, GIMP zur klassischen Bildbearbeitung, Bibble Pro zur RAW-Konvertierung, QtpfsGUI zum HDR-Berechnen, und schließlich das Triplett aus Hugin, Autopano-SIFT und Enblend zur Erstellung von Panoramabildern. Desweiteren besitze ich eine Noise Ninja-Lizenz. Unter den Linuxern gehöre ich also zu den Pragmatikern, die nicht ausschließlich freie Software benutzen. Das Backup selbst fahre ich mit rsync.