Flash pulse duration

Chuck Westfall's October Tech Tips is out, and he answers a question regarding the flash pulse duration of Canon's speedlites. Canon doesn't publish these numbers so there's quite a bit of speculation, but he points out one thing that I didn't know: at lower power levels, the xenon bulbs used in the flashes are not as efficient as they are at high power. Therefore, a flash firing at 1/16th isn't necessarily firing 16 times faster than it does at full power, since it's putting out less than 1/16th as much light per millisecond.

Without actual numbers or the tools to do some testing, it's impossible to say how much it matters. It's probably still firing faster than it would at 1/4 or 1/8, which is important in flash-based macro because your flash pulse duration is, effectively, your shutter speed.

The bit I find most interesting is where he says "I suspect that if you use a higher power setting on the 430EX to match the output of the 550EX, the flash durations from both Speedlites will end up being very similar if not identical." I've been considering the 430EX II over the 270EX, on the assumption that they'd have similar pulse durations at full power, and therefore the 430EX II would be faster since I'd be using it at lower power levels. It may be that the 270EX at 1/2 or 1/4 power isn't as much of a compromise in speed as I had thought; in terms of price and weight, it's obviously the better choice for macro.

This may seem like nitpicking, but it does have real application for the small animal photography I like to do. On a warm, sunny day, it's simply not possible to get a sharp image of a fast-moving insect without a flash pulse fast enough to freeze its motion. 1/250th of a second is a looong time in that shooting scenario.

Digikam

I'm a long-time user of Linux, and one of the minor annoyances I put up with in photography is the need to use Windows for an efficient workflow with good post-processing control. I've been dual-booting with Ubuntu for about a year now, and had frankly stopped really using it because of a few problems I was never able to resolve. I've always been more of a Gentoo guy, and what with their tenth anniversary this month, I decided to switch back. Except for this past year, I've used it as my primary OS since 2002, so even though it's a lot more DIY, I'm quite comfortable with it.

Anyhow, I've been looking more seriously into Linux RAW processing software. I know there are some really powerful options out there, but I honestly find a lot of that power is more than I need. I've currently got the latest beta of Digikam installed and I think it's about 95% of what I want, but there's still a lot I need to learn about it.

I'll be looking closely at its output later, and hopefully it'll turn out to be a good alternative to Lightroom or even DPP.

Lightroom vs. DPP comparison

Update: I see Google still sends people here when they look for this comparison, so I'd like to point out that this post is outdated.  Lightroom 3's noise reduction is much, much better than either of these two, and I don't have any of these problems with it.

I've put together two 100% crops of a recent picture, comparing the results from Lightroom 2.5 and Digital Photo Professional 3.6.1. Where I could, I processed them identically, but generally speaking Lightroom has much finer control than DPP, so to a degree I had to just ask myself how I'd normally process the image in that program.


View original


View original

The comparisons show the problem I have with Lightroom: the JPGs I get out of it lose their texture to noise. The second crop is a perfect example. There are places that are much sharper in LR, like the tip of the flower bud, but towards the edges of the in-focus region, the fine detail is lost in the noise very quickly, and there's even some color banding in the bokeh. The DPP crop, though not as detailed in the in-focus areas, doesn't have that harsh, noisy, almost plastic texture to the bokeh and nearly-bokeh regions. Lightroom's sharpening tool, incidentally, can mask out the low-detail regions, so it didn't touch the areas I'm unhappy with.

This image was shot at ISO 200, with +0.33 exposure in both LR and DPP. Noise reduction is 3 luminance and 1 color in DPP; 24 luminance and 34 color in LR. (The DPP scale is 0-20, LR is 0-100. The color slider doesn't have much effect in either on this image, as long as it's not 0.) I don't see much improvement in LR's noise reduction below about 90, which seems unbelievably high for an ISO 200 image from a 40D, even with the background a stop or two intentionally underexposed. So I don't know what's going on here -- I have to assume I'm missing something. Do I just need to crank up the noise reduction?

Lightroom

I'm playing with the Adobe Lightroom trial again. I've used it in the past and wasn't happy with the JPGs I got out of it: there was a weird plastic texture that I think had to do with noise reduction, and the contrast just didn't seem quite there. Canon's DPP gave me much better results in that regard, even though the organization, tagging, and interface are so poor, so I never made the jump to Adobe.



But lately, the workflow issues around DPP have just gotten to me. I've caught myself letting photos sit on the camera because I don't want to deal with the ordeal of processing them in DPP. Don't get me wrong: individual photos are fine to work with, but sorting through 200 shots, deleting the rejects, and then getting to the individual picks is a pain. And that's not even looking at DPP's total inability to handle data like tags and captions, which means my DPP workflow often has to involve two, three, or sometimes four separate programs to get my work online. And Lightroom can do all that stuff easily.



So, I'm reading up on Lightroom again, and already found some good advice for dealing with sharpening and tone curves in it. I'm looking through old favorites to see what I can do with them, and we'll see how it goes.