PDA

View Full Version : Sigma 18-125mm f3.5-5.6 any good?



Erwin
02-16-2005, 11:07 PM
Looking for a good all-around lens for Pentax *ist DS? A lens which has good wide angle and decent zoom. I've been looking into this Sigma lens (under $250 on ebay). Anyone have any experience with this? I've read 2 user reviews - both very positive, but I could use more feedback. The down side is suppose to be a little noisy and slow to focus in low light.
The Pentax *ist DS is my first digital camera and I bought it with the kit lens 18-55mm. A co-worker who has the digital Rebel says this lens is a little noisy - but it doesn't seem to bother me. If this Sigma is just as noisy as the Pentax kit lens, then I don't see it as being a problem.

speaklightly
02-17-2005, 07:03 AM
I am currently using that lens on my Canon EOS 20D and am quite pleased with the results. I, too, have considered getting the lens for my Pentax.

Actually I feel that the "kit lens" that came along with the Pentax 1stDS does a rather nice job of things. In practice, I tend to favor the Pentax dslr because it is smaller and more agile to use. It will be interesting to see how much smaller the Canon Digital Rebel XT really is in hand.

My Canon 20D is a great digital camera, but bigger than I really prefer.

Speaklightly

speaklightly
02-24-2005, 07:49 PM
Obviously the Tamron 28mm-75mm might be the better choice for the Pentax 1st DS. It has received glowing reviews when used with the Canon EOS 20D.

What do you think??

Speaklightly

Erwin
02-24-2005, 11:32 PM
Obviously the Tamron 28mm-75mm might be the better choice for the Pentax 1st DS. It has received glowing reviews when used with the Canon EOS 20D.

What do you think??

Speaklightly

Is there a mount for a Pentax *ist DS? I'm no camera expert, but it looks like it might be a faster focusing lens. It's F2.8 vs F3.5 on the Sigma lens. However, it doesn't have the range of the Sigma 18-125mm. There's a new one out now too, a Sigma 18-200mm. Oh well, it doesn't matter - I just purchased the Sigma 18-125mm - hope to get it by next week.

jeisner
02-25-2005, 03:20 AM
The 18-125 isn't an amazing lens, but it IS very good value for money, you shouldn't be disappointed. I don't use it everyday, but it is a handy walkaround lens if I want a wide range without carrying more than one lens.

Erwin
02-25-2005, 12:23 PM
The 18-125 isn't an amazing lens, but it IS very good value for money, you shouldn't be disappointed. I don't use it everyday, but it is a handy walkaround lens if I want a wide range without carrying more than one lens.

If you own the lens, can you elaborate? Do you use a Pentax *ist DS with it? What's bad about the lens? How does the quality compare with the kit lens that comes with the Pentax (18-55mm) ? If it has the same picture quality as the Pentax 18-55mm, then I know I'll be a happy camper. I just need a longer zoom.

jeisner
02-25-2005, 01:43 PM
I have conducted a lot of tests on the lens wigth the *ist DS. Basically it works very well, it has minor distortion at the edges, not a big deal. The biggest problem is it shares Sigmas usual backfocus issue, that I have heard many people report on different Sigma lenses. It is all covered in the thread below, notice I have replied to the inital post in the thread a few times giving more details and comparisons......

link (http://forums.dpreview.com/forums/read.asp?forum=1036&message=12164248)

gary_hendricks
02-25-2005, 04:44 PM
Looking for a good all-around lens for Pentax *ist DS? A lens which has good wide angle and decent zoom. I've been looking into this Sigma lens (under $250 on ebay). Anyone have any experience with this? I've read 2 user reviews - both very positive, but I could use more feedback. The down side is suppose to be a little noisy and slow to focus in low light.
The Pentax *ist DS is my first digital camera and I bought it with the kit lens 18-55mm. A co-worker who has the digital Rebel says this lens is a little noisy - but it doesn't seem to bother me. If this Sigma is just as noisy as the Pentax kit lens, then I don't see it as being a problem.

The default lens kit that comes with the Pentax is pretty decent.

Erwin
03-03-2005, 02:47 PM
All shots taken within a 10 minute window with camera mounted on tripod, in Av mode and using Auto Focus - as AF accuracy plays a part in the test also.

Interesting link with the comparison using the 18-125mm sigma lens. I'd like to re-create this back-focus problem. I'm not sure how you take a shot with a 10 minute window - can you explain this? Thanks.

My initial reaction to the lens (before using it) was that it didn't have the quality feel that the Pentax kit 18-55mm lens has. However, once I started to take a few shots - it seems fine. Since I'm a beginner, I don't have the eye on how to distinguish what's good and what's not so good - but so far I'm happy with my purchase.

jeisner
03-03-2005, 06:54 PM
I'd like to re-create this back-focus problem.

OK, well mount the camera on a tripod, zoom out to 18mm and widest appeture (f3.5) and use AF to focus and then take a shot. Now use manual focus to focus the camera and take your shot. Which is clearer, the MF by far ??? Conduct the same test at higher apetures or over about 50mm and the problem will not occur!!!

With some models of Sigma lenses, you can actually use 18mm at f3.5 and AF and shoot then change apeture to say f5.6 and half press the shutter button and you can see the focus change.... shouldn't happen, especially if your pointing straight on into a brick wall like I was.... (I have seen this reported from Pentax, Nikon and Canon users of various Sigma zoom lenses, my Sigma 50mm DG EX Macro does NOT display this same backfocus issue)

I have noticed in in real world shots too, I have used spot focus and focused on a tree a couple of meters in front of me (18mm f3.5) and when I reviewed the photo the tree was not in focus, but another tree 1-2 meters back is perfectly in focus, this happens consistantly when both wide angle and wide open.


I'm not sure how you take a shot with a 10 minute window - can you explain this?

Yep I took the shots with the 18-125 and the 28mm and 50mm over a 10 minute time frame, ie I didn't take the 18-125 shots in the morning and the 28mm at lunch time and the 50mm in poorer light in the afternoon. Basically I am trying to say they were all taken within a short time frame in the same lighting conditions (clear sky that day BTW),,,