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02-24-2011, 10:49 AM - 5 Likes   #1
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Sigma 120-400 v. Pentax DA*300--my thoughts


I thought I would review my experience with the Sigma 120-400 and the Pentax DA*300. The Sigma I had is the new version with the OS feature. Both have 77mm filter requirements. I use Rodenstock filters. I also shoot in Raw and shoot with a K5 and K7, but only used the lenses with my K5.

First, my thoughts are of a beginner with large telephoto lenses. I have made significant improvements in my studio fashion/glamour and martial arts shooting, but I want to do some outdoor nature work and thought I would try these two lenses. So, please take my comments as someone who clearly is not an expert.

Both of these lenses are very different and it is perhaps unfair to do a direct comparison. The Sigma is a budget minded higher end zoom and the Pentax is a high end prime. They are not terribly different in price, but the Pentax is more expensive. Both lenses represent a significant expense, however, and given the limited telephoto options for Pentax, these lenses often get mentioned together.

So, even though a direct comparison is not quite fair, my sense from reading the forum and other Internet blogs, is that there is interest in comparing the two.

I will post a few pictures when I have a chance and have access to my computer that has the images, though, they are pretty basic images. I used the lenses in and around our front yard here in central Maine, USA, and then in downtown Portland, Maine, on a very sunny day at Noon time. Here in Maine it is hilly and there are lots of trees, so shade and forest are conditions in which it is common to shoot.

Build quality: both are well built. I give the edge to the Pentax. It feels more solid, though, as a prime, it has fewer moving parts. Nonetheless, the Sigma is well built and very attractive. The Sigma also comes with a very nice well cushioned lens case and shoulder strap (the Pentax with a nice, but basic soft lens case). You might want to replace the Sigma strap with a neoprene strap, but nevertheless, the Sigma is well packaged and put together. Of course, the Pentax is weather sealed and the Sigma is not. I am unsure how often I will shoot in the rain, but there is a comfort level of knowing an inadvertent drip or splash of rain or splash from a lake will not hurt the lens or camera.

AF speed: I am not an expert and did not take a great amount of time comparing the two. I think they were about equal with a slight edge to the Sigma. Both focus quietly and relatively quickly, though neither are speed demons. Also, both apparently do not have focus limiters and when they get out of focus (like when you are trying to focus far away and the lens will focus on a branch or animal that you did not intend, it can take a bit for the lens to focus on what you were initially try to focus upon). So, there can be some hunting with both. This probably shows my lack of experience with large telephoto lenses, as I suspect when focusing in the distance it can be easy to lock on things that you did not intend.

Flexibility: of course, the Sigma is more flexible given that it is a zoom. The Pentax is at a nice 300 mm length, but it is only at that length. This is not really a weakness of the Pentax, just the way it is made. Still the Sigma provides for greater flexibility.

Weight: though the Sigma may be more flexible as a zoom, having the two side by side really allowed me to compare them. I am a big guy. I competed in Powerlifting and have been doing martial arts for the last dozen or so years and I do not mind carrying loads of equipment around all day. I do it all of the time (we have 3 children). Shooting with a large lens, though, takes skill and no matter what, you cannot get away from the fact that large lenses are tougher to balance and hold still. I used the lenses hand held and on a Manfrotto monopod. I shot from 1/180 to 1/750. The Sigma is significantly heavier than the Pentax in real life terms, and is bigger, and zooms by extending.

Can people, especially those with experience with large telephoto lenses, get good or even great pictures, at slower exposure times? Yes, but for me and I suspect most, the failures will far outweigh the successes. I am sure with better technique my percentages will increase, but fast shutter speeds really are the order of the day—and there is no surprise in that.

Which leads me to another area--Optical quality and ISO concerns: the Pentax was sharp at f/4, very sharp at f/4.5 and peaked a bit more in the f/5.6—f/8 range. All images were nice and contrasty.

The Sigma was soft until f/8 and even by then or through to f/11 was not as sharp as the Pentax, though the Sigma did sharpen up at those focal lengths. What was very obvious was the lack of contrast. The Sigma images were very flat and dull at all focal lengths, though things did improve as I stopped down. Nonetheless, the difference with the Pentax was significant.

Which brings me to my next concern: ISO. I am shooting with a k5, and it is a great camera, but it is not a magician. The Sigma becomes f/5.6 a bit around 230mm, (it stays f/4.5 to about 200mm, then jumps to f/5, then eventually to f/5.6 near 230mm). The Sigma really needs to be used at or around f/8 or above, really f/11 I think, at least my copy. That means unless I was shooting in the daytime on a sunny day, high ISO was needed.

When I set the camera to a shutter speed and aperture and let the camera meter for ISO, with the Sigma I regularly shot at or near ISO 2000 and often at 3200, in the later afternoon and even during the mid afternoon, as I shot towards the ground, in the trees, and away from the sky.

When I shot on a very sunny day sunny day the Sigma did much better and I was able to shoot at or near ISO 400-560, but here in Maine it is hilly and forested, which is why I want to shoot some nature oriented images. It also gets darker early for a good part of the year. As such, keep in mind that shooting at f/8 and above means higher ISOs. Does that mean you can’t get good or even great shots, especially with a little help in post? Of course, not, but again, no matter what the k5 at ISO 3200 is not equal to ISO 200.

None of this was a surprise, but again, it really is made much more significant when you have the two lenses to directly compare and you are (I am) a beginner seeing these obvious differences right in front of you.

Of course, if you were shooting nature stills on a (sturdy) tripod the issue of ISO is less significant, but the optical quality issue remains. The DA*300 benefits from a monopod or tripod. Though smaller than the Sigma, it still remains a big lens.

OS and Shake reduction: the OS works very well. I have read it can take a toll on battery life, but it worked well and seemed to be about equal to the Pentax. I did not test them thoroughly so I do not know if one is a bit better than the other, but the Sigma OS did fine (I turned off SR in the K5 when I used the OS, but did use either SR or OS on my monopod).

In the end, I kept the Pentax. I really wanted to keep the Sigma. It is attractive, well built, comes with a nice case, has a very desirable focal range, and was a less expensive than the Pentax. When I really saw the weight difference in terms of steady shooting, obvious optical quality difference, recognized that the Pentax was very sharp and contrasty at f/4.5, and added the weather sealing, I just felt the difference was clear. I was saddened to return the Sigma. I really wanted to keep it, but the differences were obvious.

I hope this helps people considering these two lenses.

Last edited by candgpics; 02-24-2011 at 12:28 PM.
02-24-2011, 11:21 AM   #2
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Thanks ! I've been looking at the DA* 300mm, and was wondering if there was a good zoom out there that would give me more flexibility for close to the same IQ. Your review answers that question admirably. I'm now sold on the DA* 300.

NaCl(my bank account now hates you)H2O
02-24-2011, 11:50 AM   #3
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Glad it was helpful. Neither lens is cheap, and the DA*300 might well be my last procurement for a while. Hopefully, as the Spring comes I will get some good images on the coast and post some.

Thanx so much.
02-24-2011, 11:55 AM   #4
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Thanks for the feedback.... I wonder though if somebody did a direct comparison between DA*300 and DA*60-250....

02-24-2011, 12:27 PM - 1 Like   #5
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I had the 60-250 and returned it. At the time I needed something else. It is a very nice lens, built well, just like the DA*300. It is heavier than the DA* 50-135 and built more solidly. Weight and build quality are on par with the DA*300. Very similar performance as to the DA*300. It was sharp at f/4, very sharp at f/5.6. Focus speed was about the same as the DA*300. It is a heavy lens. I thought about using it and selling the 50-135, but I like the 50-135. It is built well, but still pretty light. A tripod or mono pod is not necessary for most use. I think the 60-250, like the DA*300 benefits from a monopod or tripod.

The 60-250 did have a lot of focus breathing, though. This was something I learned about after I bought the lens. I probably will not state it precisely correctly, but in short, the closer your subject is to you, especially at fairly close distances, 30 feet or so, the zoom is probably around 200mm, not 250mm. Of course, at that close of a distance perhaps a long zoom is not really needed, but when you are in the stands at a baseball game for your chhildren, you may not have the flexibility to move. At greater distances, especially as you focus very far away, the zoom is closer to and reaches 250mm.

I am very happy I have the 300mm. The difference is not that great in terms of 250mm v 300mm, but every mm of focal length counts especially since after the DA*300 there are few choices out there. There is the Bigma at 50-500, but my sense is that given the reviews, it will behave more like the 120-400. Perhaps after I get some experience under my belt Pentax will have released a longer lense or I might find an FA 600 on the used market that will not break the bank.

Hope the above is helpful.

Last edited by candgpics; 02-24-2011 at 09:35 PM.
02-25-2011, 10:58 AM   #6
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Just thought I would add that the DA*300 has nice bokeh. I have taken some images of my children playing. The lens really was not the right tool for the job, but it was nice to use the lens to practice. The images were nice and contrasty and the keepers had a nice pleasing blurred background. I will note that I did get a number of stares from onlookers. Of course, I did not mind at all.
02-27-2011, 07:58 AM   #7
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Very interesting and good comparison, I have the Sigma 120-400 HSM without the OS and the DA*300 and think I can confirm most and maybe all your conclusions. One of my favorite subjects is sports and for some sports I just need the flexability of the Sigma. If however sharpness and max aperture is required due to bad light the DA*300 will be mounted.
The Sigma is almost always used on a Manfrotto monopod, but I may take the DA*300 out for a walk wihtout the monopod.
I have used both lenses extensively on my K7 which is now replaced by a K5. Sofar I have not done real shooting with my K5.
02-27-2011, 04:23 PM   #8
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Thanx so much for the confirmation. I really am a beginner with large telephoto lenses so it is nice to know I was accurately comparing the two lenses. When I have a chance I will post a few images I took with both lenses.

05-14-2011, 06:58 AM   #9
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Me too.

I was comparing the Sigma 120 to the DA*60-250. The thing that killed me with the Sigma was it's flat, lack of sharpness in the long end. IN the end, I decided I was better off with a sharp 250mm and a sharp f.4 at 250mm than images that for me were unusable. I will say that for birds at my feeder, the Sigma was the better lens. As I find with my Sigma 70-300, none of the image problems I saw with a longer reach were apparent when the object was 10-40 feet from the camera. For birds at my feeder, the Sigma 70-300 outperforms my DA*60-250, in that there is a lot more magnification in the Sigma, in fact the image size of the Sigma at 240 is considerably more magnified than the Pentax at 250mm.

The 120-400 also produced the worst purple fringing I've ever seen on one of my test images. In the end, it was IQ at long distance that made me take this lens back. I could set up a tripod, use a delay and stop down and still get a crappy image. That's just unacceptable. If I take the time to do things right, the lens has to perform. The 120-400 didn't. My DA*60250 doesn't give me as much reach, but what I get is tack sharp. A much more desirable outcome.
05-14-2011, 10:33 AM   #10
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Thanks for the comparising and comments about 60-250. I'm an owner of the DA*60-250 since yesterday and wend out for a shoot-out today. Getting back on that later when pictures are sorted out. I used a monopod today and that is very usefull with such a heavy lens.
05-14-2011, 12:45 PM   #11
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Thanks a lot for the review. Many times, because of the budget, I have been thinking of the 120-400. But, looks like I rather wait for some more time, save some money and then go for DA*300.
05-14-2011, 04:36 PM   #12
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good review.. I am leaning toward the 60-250. I need a good zoom. A little put off by the reviews of the4 Sigma..
05-14-2011, 07:30 PM   #13
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very nice review/comparison. Please upload some pics also; thanks.
05-15-2011, 12:50 AM   #14
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Just to throw a cat amongst the pigeons, how would the Sigma EX DG 100-300mm f/4 compare to the Pentax DA* 300mm?

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