Interesting...

Everyone correctly guessed on the 50-135mm and the 50mm.
But everyone got the 18-55 and 18-200 mixed.

I normally shoot with wider apertures , but I think John has a good point. I may try again with f/8.0 and see how they compare.

Anyway, the order is:
2007-08-16_IGP6620.jpg : Sigma 18-200
2007-08-16_IGP6621.jpg : Pentax 50mm f/1.4
2007-08-16_IGP6624.jpg : Pentax 18-55 kit
2007-08-16_IGP6625.jpg : Pentax DA* 50-135

Honestly, not sure why the 50mm prime isn't the top dog. I may want to re-run. Or I may just leave the Six-Sigma testing to the scientists. (I am a quality assurance software engineer by day, no need to continue when I get home... I just can't help it. )
I think the test is good enough for comparison sake, but I wouldn't make bets on consistency or relevance in all possible cases.

OK, so maybe it don't say much for real life, but I know some people like to "see" examples for new items.

I took the same photo with the following lenses:
Pentax 18-55mm kit lens
Pentax SMC-FA 50mm f/1.4 prime
Pentax DA* 50-135mm
Sigma DC 18-200mm

All lenses set at 50mm or closest value to fit the object in the frame as close to identical as possible. Also set to the least common denominator of f/5.6 so all images would be as consistent as possible for each lens.
The camera (K10D) was of course on tripod, no SR.
Lighting was consistent via Wireless AF-540-FGZ bounced off ceiling.
RAW images were processed using SilkyPix with all default settings. (both JPEG and TIFs are available)

The images are 100% crops to show a smaller section of the image. The images are the same size in pixels, but due to slight differences in lenses they may show slightly different amounts of the subject. (I tried to keep things as close as possible on the camera end, but some human error still prevails)

Hopefully the test was consistent enough to be worthwhile to some.

You can view the four images here:
http://moringello-east.no-ip.com:8080/public/images/lens_test/

The tifs folder contains the same images in TIFF format (duh). They might show a bit more detail, but I really don't see it. I think the jpeg images show enough detail to show the differences.

2007-08-16_IGP6620.jpg : <lens ???>
2007-08-16_IGP6621.jpg : <lens ???>
2007-08-16_IGP6624.jpg : <lens ???>
2007-08-16_IGP6625.jpg : <lens ???>

Can anyone match up the correct lens with the corresponding image?
At least try to guess the DA* 50-135.

Thanks, the Ice portion was an interesting one to do. I laid the cubes on blue blanket over a glass table. The wireless flash was fired from underneath to give the lighting effect I wanted.

I normally love using the remote flashes, but I didn't use flash on the Stone or Iron images. Gotta love those big 500W halogen work shop lights - although they are be better in the winter as they heat up a small room pretty quickly.

Same thing happened with my istD but in the first two days. Argh!
Nothing would clean that out. (didn't know the screen was removable at the time). You'll probably have to remove the focus screen to clean it. But since you're looking to replace that anyway, kill two birds with one stone.

From what I hear, these focus screens are very helpful for manual focus, but metering is only accurate at F/2.8 or wider (I think). So you may need to manually meter if you have lenses that don't open that far up.

D-Lite 4's here as well. Love 'em.
I've been using a 540 and 360 for a while, but they tend to be a little bit dim in some situations where the lights may need to be several feet back and shooting through an umbrella or soft box.

I picked up an tiny, old, dumb hot shoe flash (with safe trigger voltage) for 50 cents from a garage sale and use that as a strobe trigger. It is too small to add significant light to the scene. With that I don't have to worry about pre-flash PTTL "stuff", cables, or other extra equipment, etc...

Anyway, bare bulb, the D-lite 4'a seem to be about two stops brighter than the 540 according to my light meter at 10 feet. But through a soft box, I get as much as a 4 stop difference. Perhaps my technique is flawed, but for me it makes quite a difference. (I've see amazing stuff on sites like Strobist.com, so perhaps its just me...)

If I need F8 or higher, the 540s just don't seem to do it.
I tend to do more animal photos. Very short DOF, slower shutter speeds, and six second recharge rates just don't do well for much of the time.

For small, closer work or with f4-5.6 the 540s will likely be fine.
Although for children, you might look into something with faster recharge rate than the AF540FGZ's six second rate (I've had as little as 5 seconds with new batteries but after about 20 shots, mine drops to seven seconds -- others have had better results, but I'm just sayin...
The D-Lite 4's generally recharge in under 2 seconds at full power, which I don't always need. So I'm getting 1 second or less in many situations.

Anyone hear from thomasthehymer for the next week's subject:

I resemble that remark!

Hell, you didn't think I went in there with the camera did you? I stood outside the stall where it was safe and dry!! I'm not stoopid!

Yeah, my head may be full of rocks, but I just can't sit and leave such things untested. At age five the parents couldn't leave anything laying out... 10 minutes and I'd have it apart to see how it worked. Teachers didn't like me in school either -- too many questions.

TRUE! I wouldn't put in a fish tank of water, but if it can't handle "rain" I'd be disappointed.

Of course, maybe this is a bit harder rain than specs allow and I wouldn't expect to be there for an hour, but now I feel I can safely run to cover without hunching over frozen like a scared puppy trying to keep the camera dry until I pull out my grocery bags.

Wonder how it would handle Maid of the Mist boat ride at Niagara Falls? I might still want to wrap in in plastic for that.