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08-28-2007, 09:01 AM   #31
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But Chikenhawk talked about the 16-45 being great because of the constant f4. But for instance the sigma 17-70 2.8-4.5 could also be used at a constant f4 at least between 17-60mm, so why isn’t that equally great?

Edit, ops I didn't see your last post.

08-28-2007, 09:17 AM   #32
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Glad we're all squared away right now I seriously considered the 17-70mm, and still think it would be a great lens for me (why do I only find quarters under the couch cushions, and NOT $100 bills?) I opted for the Tamron 28-75mm, because I really needed f/2.8 at the long end.

I believe (again, just a gut feeling as I haven't tried either) that the Sigma 17-70 would be a better bet than the Pentax 16-45. I don't consider the f/4 vs. f/4.5 significant enough to warrant "points" for the Pentax. About the only plus for the Pentax (subjective rendering opinions aside) is the extra mm on the wide end (but that's why I have my 10-20mm!)

The Sigma gives you f/2.8 @ 17mm, MUCH longer range (45 vs. 70mm) and closer focusing distance.

(looks under cubicle for any stray money.....)

How's the weather in Sweden?
08-28-2007, 10:39 AM   #33
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QuoteOriginally posted by egordon99 Quote
(but that's why I have my 10-20mm!)
Then you probably wouldn't be interested in the slightly extra wide angle.

QuoteOriginally posted by egordon99 Quote
The Sigma gives you f/2.8 @ 17mm, MUCH longer range (45 vs. 70mm) and closer focusing distance.
Everything I've read suggests that f/2.8 isn't very usable, and it's really more of a f/4.
08-28-2007, 09:59 PM   #34
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QuoteOriginally posted by Gimbal Quote
But Chikenhawk talked about the 16-45 being great because of the constant f4. But for instance the sigma 17-70 2.8-4.5 could also be used at a constant f4 at least between 17-60mm, so why isnít that equally great?
Yes, the lens can stay at f4.0, but the exposure changes with zoom. That is not a problem unless you are shooting in M mode. With a constant aperture lens, the exposure stays the same no matter the focal length. With a variable aperture zoom, the exposure constantly changes. If you left it on f4.0 between 17-60mm, at 17 the exposure would be correct but by the time you got to 60mm, you would be a half stop underexposed. Note this only applies when in M mode and only applies when you are metering the light falling on the subject using either a grey card or a light meter.

Many people don't realize variable aperture lenses change their exposure throughout the zoom range because any program or priority modes take care of that for you. If you don't believe me, pick a large homogenous wall, use MF, set the camera to a convenient f-stop in Av mode and watch the shutter speed change as you zoom in and out. Now try it with a constant aperture zoom, and the shutter speed stays roughly the same.

But this advantage of constant aperture lenses really applies to the way I shoot, and mostly outdoors with fill flash. For most people, they would not even notice the difference.

(When I use fill flash, I meter the background in M mode, set the 360 or 540 flash to P-TTL and dial in about -1.0 or -1.5 EV flash compensation. This gives me a 2:1 or 3:1 fill ratio, which is just about perfect starting point for most of my shots. If I tried to shoot fill flash in any other mode than M, my aged and slow-witted brain would probably explode with the complication.)

08-28-2007, 11:56 PM   #35
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QuoteOriginally posted by bjsmith Quote
Everything I've read suggests that f/2.8 isn't very usable, and it's really more of a f/4.
Good to know, I'll proceed to throw away my pics now :-P

But really, really, really, really, really it depends on the subject. Unless you're shooting studio shots you may not notice slight vignetting (you're shooting at 2.8 in low light anyway) or softness at wide open. Even if you do, it's definitely better than not getting that steady available light shot at all.

For what it's worth I wouldn't have for my everyday walkaround lens that doesn't do 2.8. Perhaps I would, if we didn't have for 2/3 of a year pretty constant low-light weather over here...
08-30-2007, 09:39 AM   #36
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QuoteOriginally posted by bjsmith Quote
That's a small difference, and I'd go for the Sigma 10-20mm then.
Yes, 102.5 degrees is much better than only 83.3 degrees.
But in all honesty, I'm finding 83.3 degrees to be very satisfying, and I'm not whipping out my Zenitar 16mm fisheye anymore.

Actually, I'm finding the difference between 16mm and 18mm to be very, very significant for myself, even if it's just a tad less than 10 degrees overall.

.
Here in UK, it's usually 16-45 that's more expansive (generaly around 330-350 pouds) sigma 10-20 is around 300 generaly. And that price of 259 for DA16-45 I only saw in one shop...
I don't really know if I need more than 83.3 degrees. But I do mostly landscapes, so my kit is mostly at 18mm. To be able to zoom oun just another 2 mm and then cover the same range, doesn't make a big sense to me. Especialy if I can't afford to buy both 10-20 and 16-45
Another contenders would be DA12-24 (very pricey) and DA14 (limited versatility since no zoom, better CA and distortion though)
Anyway I can't decide which one shall I splash my hard saved cash for
08-30-2007, 09:52 AM   #37
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QuoteOriginally posted by axl Quote
Here in UK, it's usually 16-45 that's more expansive (generaly around 330-350 pouds) sigma 10-20 is around 300 generaly. And that price of 259 for DA16-45 I only saw in one shop...
Ouch!
I mean, the USD isn't exactly "strong" these days and I got my DA 16-45 for US$359 - US$100 rebate.
The Sigma DC EX 10-20 f/4-5.6 is US$450 on a good day.
The Sigma DC 17-70 f/2.8-4.5 is US$350 on sale as well.
The DA 12-24 f/4 is US$700 - US$100 rebate.

QuoteOriginally posted by axl Quote
I don't really know if I need more than 83.3 degrees.
I have the Zenitar 16mm fisheye f/2.8 and on the APS-C cropped sensor, it only gives me another 20 degrees or so.
So in all honesty, I'm rarely putting the Zenitar on anymore.

And even though the difference between the DA 18-55 and DA 16-45 is even less, I do really find 24.5mm equivalent 83 degrees to be the "sweet spot,"
and a "significant upgrade" from the 27.5mm equivalent 76 degrees of the DA 18-55.
Weird, but it's just what I feel.
08-30-2007, 03:26 PM   #38
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I agree with BJ. I agonized over which of these two lenses to buy and went with the 16-45. That extra bit of wide angle makes a huge difference to me. It also bugged me that the Sigma wouldn't record the lens dta correctly in the EXIF file. (minor I know but I am anal that way)

10-11-2009, 09:30 PM   #39
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I know this is an old thread but I need to comment.

I initially bought my K7 with a 17-70 which had focus issues, swapped it for another copy which seemed to be sharper but I found the colours dull and muted and eventually the lense creep was beyond acceptable. However I loved its macro performance and f stops.

I ended up swapping it over for a Pentax 16-45 which I was mostly happy with, loved the colours, the constant F4 and its extra width. However I really hated its build quality, I found the lense barrel had MORE than acceptable play at widest zoom and I found the lense just wasnt long enough.

After a few months I came across OLD forgotten stock at my work, a Sigma 17-70mm which was a couple of years old and just been sitting in the cupboard practically unused.

I asked to borrow it to shoot an event and WOW that night and day difference between it and the two previous copies was more than obvious. Images were razor sharp even at the widest settings, I immediately plonked money down for this lense and never looked back.

Sure it's not perfect but for the money it's probably one of the best everyday lenses available for the pentax IMHO.
10-06-2010, 03:11 PM   #40
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QuoteOriginally posted by aabram Quote
I was once in the same boat as you, deciding between those two. But in terms of length these two are really different beasts. If you feel that kit lens is too short at times, then 16-45 will be even shorter. I went for 17-70 for two reasons: for its great and useful range and f2.8 at the wide end, compared to f4.0 (although constant throughout) for Pentax. Shooting indoors f2.8 does come handy.

Also, as I mentioned in other thread - try to think what ranges or what lenses will you get next. If you're planning to get 12-24 at some point, you may want to avoid too much overlapping with ranges.

My Sigma 17-70 samples can be found here. There are no people or party shots though, these I tend to keep private ;-)
Great photos - you know sometimes you see a another photographers pictures and you know you are going to like their work almost instantly ?

Well that just happened when I viewed yours !
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