Raw Matter - Photography

On Bad Lenses

nospam@example.com (Adrian von Bidder) — Tue, 22 Mar 2011 09:48:22 +0100

I, and maybe some others, wondered why people would (have to) send new lenses back claiming that they got a “bad copy” so often. I couldn't imagine quality control being so bad that two out of three (at least that's the impression I got from reading the occasional foto discussion forum) lenses are bad.

It turns out that it is not only people needing to be pampered and having the impression that their second (identical) copy of the expensive new lens is better. Nor is it bad QA by the manufacturers alone. Fact is that todays high megapixel cameras are at the limit of the manufacturing precision that can be achieved at a reasonable price. Roger Cicala (LensRentals.com, so he occasionally does have a lens or two at his place) wrote some very interesting articles about this topic which I discovered just now as they were featured on canonrumors

(In case you're wondering: No, I don't see any issues with my new 70-200mm, just coincidence that I'm reading this just after getting a new lens. When I upgrade my camera body to something like a 5D MkII I will take a very close look at my Tokina 11-16 though, where I don't trust the AF 100%. On the 10MP Canon 40D it's a great lens, so I'm quite happy for now, but it seems strange that when I release and half-press the shutter again after having focused, the focus will sometimes move a tiny bit again. Haven't noticed this behaviour on the other lenses.)

New Toy

nospam@example.com (Adrian von Bidder) — Thu, 10 Mar 2011 21:16:58 +0100

Getting a birthday present is always nice, of course. This one made me itch to go outside and hunt for nice motifs, though ... Images are straight from the camera, just a bit cropped (look at the EXIF if you feel like it.) If you don't want to look at the EXIF: the beautiful new lens is the Canon Canon EF 70-200mm 1:2.8 L IS II USM (like all manufacturers, Canon likes to collect funny abbreviations at the end of their product names — though I feel they're not as bad as some...), and I truly like what I'm seeing so far. That this lens has excellent sharpness goes without saying (especially on the 40D with modest 10MPixel on a crop sensor), see the comparison with the old EF 100-300mm f/4.5-5.6 USM (the piccolo picture.) Beyond sharpness, there's the 1:2.8 aperture, the IS really keeps what it promises (and is absolutely silent), and AF is quiet and ultra fast as well. I've only got it today, so I took only a few shots — I'm confident that CA, flare resistance etc. will live up to reputation though. Now I'm really starting about a full frame camera with higher MP count to take full advantage of my lenses (you may remember that I quite like decent equipment; the wideangle is said to be usable for full frame down to ca. 14mm although it's really designed for crop sensor...)

The obvious question is if I really can take better pictures just because I'm now lugging around a 6kg bag of stuff ... but honestly, having a telephoto lens without image stabilisation was a pain, so getting the old tele replaced was the obvious next step.

Oh yes, and: see you in Banja Luka! :-)

Toys, Number Three

nospam@example.com (Adrian von Bidder) — Tue, 01 Dec 2009 22:20:09 +0100

Biggest, in terms of money involved, piece of equipment is a nice piece of glass to put in front of our camera.

Since my wife had been using a Canon SLR since forever (and we stayed with that when moving from the EOS 300 to the current EOS 40D), the choices to upgrade from the kit EF-S 17-85mm f/4-5.6 basically have been:

EF-S 15-85mm f/3.5-5.6 IS USM: since it's been announced with the 18Mp 7D it should be quite good on the 10Mp 40D. Newest design, certainly one of the best IS on Canon, true wide angle.
EF 24-70mm f/2.8 L USM: The old trusted one. No IS, but a constant f/2.8. Narrowest zoom range of the lot. A real tank, at almost 1kg.
EF 24-105mm f/4 L IS USM: The other full frame L lens. Not quite as big, longer, but only f/4.
EF 24-70mm f/2.8 L IS USM: including waiting for it to be announced and available, of course.

In the end I got the EF 24-70mm f/2.8 L USM, because the EOS 40D is no high ISO monster (we don't plan to upgrade immediately.) Also: I bought the Tokina AT-X 116 PRO DX (11-16mm, f/2.8) a while back and we're quite happy with that so wide-angle is covered. And since we're often shooting indoors (family and other events), f/2.8 is a big plus. On the tele end, there's quite a gap from the 24-70 to the old EF 100-300mm f/4.5-5.6 USM [age of the page to reflect the age of the lens ;-) ] but then the latter is probably the next lens to be replaced anyway.

Since I only got 24-70 I can not directly compare these lenses. But after a few early tests I think I'm happy with the 24-70: while it seems to be a bit soft wide open at 24mm and at 70mm, it seems to be very sharp center to edge even at f/2.8 when used in the 35-50mm range. (Note that the 40D is a crop sensor camera, so I'm nicely using the sharp “center” area of a lens designed for full frame!) Yes, it's huge, so for casual walking around the 17-85mm will probably still get some use. Time will tell. And since it can, potentially at least, be used on a a EOS 5D Mk II, I now have another gadget to covet. Although this would mean giving up the Tokina 11-16mm. Anyway, not for quite some time yet...

(The test also included the venerable EF 50mm f/1.8, Mk I, and I must say I'm quite surprised how sharp that one is in the f/4 to f/11 range.)

DeviantArt

nospam@example.com (Adrian von Bidder) — Tue, 03 Nov 2009 21:36:39 +0100

I am eager to get feedback on some of my pictures. Some people already liked them, so the ego is quite well right now... :-)

Color Calibration

nospam@example.com (Adrian von Bidder) — Fri, 23 Oct 2009 15:48:24 +0200

A topic I've been trying to understand more about for some time is color calibration. I've used lprof to get a very rough starting point for my old CRT (sorely in need of replacement by now...)

Since hardware colorimeters are not cheap and probably not many can be used with Linux (I've not really looked, to be honest) I've wondered if I couldn't use the one device that is (should be) calibrated that I already have: my camera. With some kind of feedback loop like “shoot screen, analyze img file, adjust settings, shoot again” (and the same process for the printer, and, possibly a bit more error prone since the freshly calibrated printer would be used to produce the template, the scanner), shouldn't it be possible to arrive at sane settings? The camera explicitly allows using sRGB or Adobe RGB color model, so I'd think the colors should be more or less narrowly defined, at least when shooting raw or using manual white balance.

(Another thought: I have a dual screen system. Can X even do this? And if X can do it, is it possible to tell Gimp to set this up? But this is just idle speculatio. I've not really looked at Google's results yet, either.)

Update: Haven't really thought about ambient light. But the display emits light, so I'd shoot the screen in a darkened room, with white balance of the camera set manually. OTOH — thanks Joël — if I can get a colorimeter for not much above 100$, it's not worth investing too much time. I had always thought these devices were much more expensive. divide_by_zero Yes, I know CRT are usually much better than LCD, but OTOH my screen apparently starts to show its age: it will suddenly, and visibly, change brightness and color every few hours. I suspect the high voltage circuitry is not too stable anymore... And I won't buy another CRT, those things are just huge...

Build your own lens

nospam@example.com (Adrian von Bidder) — Fri, 13 Mar 2009 17:46:23 +0100

Just stumbled on the Optical RayTracer by Paul Lutus, a fun program to play around with optical lenses. After an initial look around, the next obvious step was, of course, to re-build an existing lens; I guess it worked somewhat. Compare the screenshot below with the block diagram of Canon's EF 50mm 1.8 lens. (No, I'm not paid by Canon, it's just the brand of the camera we own, and it's probably one of the simplest lenses around, too. Which, no surprise, we happen to own as well.)

Optical RayTracer is not in Debian yet. I've asked Paul if he'd mind if I did a package. Not within the next two, three weeks, though, sorry.

The Canon EF 50mm 1.8 re-built in Optical Raytracer

(Note to self: also look at OpenRayTrace)