[WMBP]

I'm considering:

• the Pentax DA 16-45 f/4. Backordered at most of the places with the best prices, but looks like I could get it under $400 when it becomes available.
• the Sigma 17-70 f/2.8-4.5. Faster, longer. Can get it for $325 shipped on eBay. Photozone.de gives it a pretty good review. Any downside??

I have both of these and they're both good. Actually, the Pentax 16-45 f/4 is terrific, and a great bargain at the price, but I often find myself wanting to reach a little further than 45mm. In the past, I owned both the Tamron 28-75 f/2.8 and the Sigma 28-70 f/2.8. Liked 'em both but had the opposite problem: they weren't wide enough. The Sigma 17-70 f/2.8-4.5 macro is just about right, in my opinion, a nearly perfect basic, everyday lens.

I also have the Sigma 18-50 f/2.8, which I bought mainly for wedding use. I decided I wanted that constant f/2.8. It's a pretty good lens but I have been less pleased with the image quality of the Sigma 18-50 than with the Pentax 16-45, even though I lose a stop switching to the Pentax lens. Still, I'd like 'em both better if they were longer.

I haven't put the Sigma 17-70 through its paces yet; just got it last week. My initial response is that it may do nicely. Here's just one bad example:



It's not a good example from which to begin evaluating the lens because it's indoor sports, lighting was awful as usual, and the image has been post-processed in Lightroom. Still, it's not a BAD result, in my opinion. I have not made my mind up yet about the lack of a constant aperture throughout the zoom. It's a about stop and a half difference between 17mm (where you get the f/2.8) and 70 (where you get the f/4.5). Shooting that volleyball game, I put the K20D into TAv mode, set the aperture to f/4.5 and left it there and it worked. Perhaps it helps to be shooting with a K20D. (Technical notes about the shot above: It was taken with a K20D at ISO 2500! Focal length for that shot = 34mm, shutter = 1/250th sec.)

If I get a chance tomorrow, I'll take another shot or two with the new lens and with the 16-45 and post here for comparison.

Will

[moxfyre]

I have both of these and they're both good. Actually, the Pentax 16-45 f/4 is terrific, and a great bargain at the price, but I often find myself wanting to reach a little further than 45mm. In the past, I owned both the Tamron 28-75 f/2.8 and the Sigma 28-70 f/2.8. Liked 'em both but had the opposite problem: they weren't wide enough. The Sigma 17-70 f/2.8-4.5 macro is just about right, in my opinion, a nearly perfect basic, everyday lens.

I also have the Sigma 18-50 f/2.8, which I bought mainly for wedding use. I decided I wanted that constant f/2.8. It's a pretty good lens but I have been less pleased with the image quality of the Sigma 18-50 than with the Pentax 16-45, even though I lose a stop switching to the Pentax lens. Still, I'd like 'em both better if they were longer.

I haven't put the Sigma 17-70 through its paces yet; just got it last week. My initial response is that it may do nicely. Here's just one bad example:

...

Will

That's really informative, Will, thank you! Sounds like the Sig 17-70 is nice indeed. My current standard zoom is the 18-55 f/3.5-5.6, so just about anything will seem faster Do I want constant 2.8, or more reach... hmmm. I have the K10D so don't have the stratospheric high ISOs of the K20D.

Can you tell me what the minimum aperture of the 17-70 is at 35mm, the normal-ish focal length?

[frank]

Can you tell me what the minimum aperture of the 17-70 is at 35mm, the normal-ish focal length?

It's F3.5 at 35mm IIRIC, F2.8 between 17 to 22mm, F4 up to 63mm, then F4.5 beyond that. Excellent lens, would be a hotter seller if it's a Pentax made lens ...

[WMBP]

Do I want constant 2.8, or more reach... hmmm.

Well, it depends on how you're shooting. Until very recently, I was shooting in M mode almost all the time (or in TAv, which is basically M with auto-ISO). When I put the aperture at f/whatever, I liked it to stay put.

But lately I've been shooting more and more in Hyperprogram mode, which has been sitting there all along, but whose brilliance only became apparent to me quite recently. Anyway, if I'm in P (hyperprogram) mode and zoom all the way from 17 to 70, I do lose, as I said earlier, about a stop and a half in the aperture (from f/2.8 to f/4.5) It's certainly not nothing, but if I really need to be shooting at f/2.8 a lot, I'll probably be using a different lens (the Sigma 18-50, or Pentax 35 f/2 or something like that). So with the Sigma 17-70, I will probably hover around f/4 as a max aperture anyway, which means I'm generally only going to lose half a stop or so, and in P mode, the camera can compensate for me either with a slightly slower shutter or, if I'm in auto-ISO, by adjusting the ISO.

Can you tell me what the minimum aperture of the 17-70 is at 35mm, the normal-ish focal length?

I just tested it with the lens: f/2.8 at 17mm; f/3.5 at 24mm; f/4 at 35mm. This is slightly different from what Frank has suggested already but only slightly. I don't usually agonize over these things, although perhaps that's because for a good while now I've mostly been using fixed-max-aperture lenses. Anyway, it's f/4 at 35mm for me, so it's not any slower overall than the Pentax 16-45.

Don't place your order yet! Give me a chance to take and post some comparison shots tomorrow. I'm up in the middle of the night now because I couldn't sleep, but I think I'm fading, so I'm going to pop off, snooze a bit, and will try to remember to get back here tomorrow.

Will

[hll]

don't go with f/4 lenses, they are very good but slow
i am a 16-45 user and it is not good for indoor shots, i think i will have the 17-50 2.8....

[frank]

don't go with f/4 lenses, they are very good but slow
i am a 16-45 user and it is not good for indoor shots, i think i will have the 17-50 2.8....

For indoor low light shots, better go w/ some fast prime lenses instead of a zoom. Even a F2.8 zoom lens isn't fast enough if you don't use a flash. But if you do use a flash, even a kit lens is capable of taking excellent indoor photos

[moxfyre]

For indoor low light shots, better go w/ some fast prime lenses instead of a zoom. Even a F2.8 zoom lens isn't fast enough if you don't use a flash. But if you do use a flash, even a kit lens is capable of taking excellent indoor photos

I have an A50 f/1.7 as well. I don't use it much because the FOV is a kind of narrow on the DSLR. But fast, wider primes are pretty expensive. The 35mm f/2 is $300 and still a stop slower than the typical "fast 50"

Are there any other options for fast "normal" primes for Pentax DSLRs?

[hll]

For indoor low light shots, better go w/ some fast prime lenses instead of a zoom. Even a F2.8 zoom lens isn't fast enough if you don't use a flash. But if you do use a flash, even a kit lens is capable of taking excellent indoor photos

yeah, 2.8 is not very good but better than f/4...
imho for kids you need a zoom lens.... they are very fast....even the wide angle is necessary...

[NaClH2O]

*snip*
Are there any other options for fast "normal" primes for Pentax DSLRs?

Don't know what you consider "normal" but Sigma makes both a 30mm F1.4 and a 28mm F1.8. I don't own either lens, and both seem to get pretty good "press". I do own the Sigma 24mm F1.8 and it is a good lens if a bit on the heavy side.

NaCl(what is 'normal' for some is 'wide' for others)H2O

[moxfyre]

Don't know what you consider "normal" but Sigma makes both a 30mm F1.4 and a 28mm F1.8. I don't own either lens, and both seem to get pretty good "press". I do own the Sigma 24mm F1.8 and it is a good lens if a bit on the heavy side.

NaCl(what is 'normal' for some is 'wide' for others)H2O

Hey, thanks NaCLH20... I did not know about either of those!

The 30 f/1.4 is pricey at $400-500, though the 28 f/1.8 is not too bad at $250-300. If they can make a full-frame FA 50 f/1.4 for <$200, why can't they make a DA 35 f/1.4 for the same price

Hmm, apparently there's also a *non-macro* Sigma 28mm f/1.8... sigma4less lists it for $180, but it is out of stock Is that discontinued? I can't find it anywhere else.

And you're right, I'm not exactly sure what's "normal" for me either! I should check and see what focal lengths I use most for candid shots... time to do some EXIF digging!

[simonkit]

I'm another very pleased Sigma 17-70 owner, I find it excellent for a walkaround and a landscape lens.

It's not just sharp but I particularly like its colour & contrast rendition. I'm intrigued to see if the Pentax version can better it, it's got a difficult task !!

simon

[WMBP]

OK, I've done a few quick test shots with both lenses: the Pentax DA 16-45 f/4 and the Sigma 17-70 f/2.8-4.5 DC Macro. Note that, on 4-1-2008, the Pentax is available from Amazon for $330; the Sigma is available from Amazon for $370. MSRP for both lenses is much higher.

You can see the photos here:

20080401 Pentax 16-45 vs Sigma 17-70

NOTE! I am not an engineer, nor a pixel peeper. I do not claim that these comparison photos are scientifically legitimate tests. It's quite possible I've made gross errors here that badly skewed the results, so I don't want anybody to be unduly influenced by my handful of photos.

On the other hand, I did use moderate care, trying to get the same shots in pretty much the same light, with pretty much the same camera and lens settings. However, everything was done hand held (no tripod). To compensate for operator error as much as possible, I took each shot a couple of times and then selected the best one for the comparison. And I did do a little post-processing in Adobe Lightroom: slight exposure fixes, clarity, and a bit of sharpening. Some of the photos were given a black and white treatment. I justify post-processing because I post-process all of my photos and I'm interested in what I can get from the image files, not what the image files look like straight from the camera.I took my shots mainly around 35mm, and avoided the max aperture settings, too. My goal has not been to identify each lens's weaknesses but rather to try to figure out the BEST that each lens can do, given my uninspiring choice of subjects, lack of time, mediocre light, etc.

Bottom line? I am not a lens connoisseur, but to my eyes, the results from the two lenses are pretty comparable, which is to say that the Sigma 17-70 seems to be a pretty decent lens. I've stared at these photos now for an hour, and I think that it's likely the Pentax shots are "better" but the superiority is slight. And of course, the Sigma's ability to cover the focal range from 45-70mm is a big mark in its favor, indeed, it's the reason I bought the lens.

I've added a couple shots taken other lenses - one by the Pentax FA 35 f/2, one by the Sigma 18-50 f/2.8 Macro - to add two more points of comparison. I wish I still owned the kit lens so I could have thrown it in there.

I also added, at the end of the album, a couple of close-focus (I won't call 'em "macro") comparisons. Although the Pentax isn't marketed as a "macro" lens, it does fairly well at close range.

For what it's worth (which ain't much)....

Will

[moxfyre]

OK, I've done a few quick test shots with both lenses: the Pentax DA 16-45 f/4 and the Sigma 17-70 f/2.8-4.5 DC Macro. Note that, on 4-1-2008, the Pentax is available from Amazon for $330; the Sigma is available from Amazon for $370. MSRP for both lenses is much higher.

Again, really useful to me! Thanks, Will.

Yeah, I can't see much difference in IQ, and I would not mind the extra speed and reach of the sigma. Though I guess the Pentax lens is more compact.

[benplaut]

Don't know what you consider "normal" but Sigma makes both a 30mm F1.4 and a 28mm F1.8. I don't own either lens, and both seem to get pretty good "press". I do own the Sigma 24mm F1.8 and it is a good lens if a bit on the heavy side.

NaCl(what is 'normal' for some is 'wide' for others)H2O

I have the 28/1.8, and find myself advertising it every day on some forum or other

It's tack sharp at f2, pretty good CA/PF/distortion, and 1:2.3 macro (very, very useful). Big, heavy, and prone to flare. Still worth it, imo