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04-02-2011, 12:14 PM   #1
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Sigma 120-400mm f4.5-5.6 DG Vs Pentax 300mm F4 SMC DA ED IF SDM

I am trying out the Sigma lens at present, before I commit to buying. I would value some member comments from anyone who has done a comparison of these two lenses. I have read various reviews of both and, of course, the Pentax lens does get a high rating - and it should be better than the Sigma, given that it is more expensive, fixed focus etc. But how much better? Eye-popping better or what?

I have shot perhaps 200 pix over the last 24 hours. The light has been overcast to a greater or lesser degree, so 200-500 ISA has been set. I have used a monopod, tripod and hand held when there is a bit of sun. As expected, at 400mm, the images are a bit soft, but here's the rub, none of the images have the 'wow' factor that I am looking for over any of the focal lengths. I have shot wide open, but I have concentrated on the f8-f11 range, as recommended in all the reviews. I can't say there is anything wrong with the lens - CA seems well controlled and even the edge sharpness is tolerable and there doesn't seem to be any marked back/front focus issues. The lens is OK, but it still seems expensive for something that is 'just OK'!

I like to shoot a bit of wildlife, landscape and anything else that takes my eye. I want longer reach than 200mm and would prefer zoom, but there really is nothing to compete with the Sigma's versatility. However, I would pay up for the Pentax 300mm and forego the zoom versatility if I can get that 'wow' factor. The camera is a Samsung GX10 (10mp).


I would really like to hear your opinions!

Thanks

Ray

04-02-2011, 02:32 PM   #2
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Hi:

Here is a short review I did of the Sigma 120-400 and the DA* 300.

Hope it is helpful.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/134439-sigma-1...-thoughts.html
04-05-2011, 08:16 AM   #3
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Ray,

There has been a lot of discussion on this topic.
lawjbm pointed out one of them.

The Sigma 120-400mm is not one of the best Sigma lenses.
Unless the copy you are testing is much better than all previous samples I've seen photo's of on this forum and review sites, I would not buy it.
The lens is at its weakest at f400mm, but that 400mm is why most people would buy it.
I bought a DA* 60-250mm + AF 1.7TC combo instead with more range and sharper results.

Have a look at this: (from the slrgear.com site)

Blur index sheet Sigma 120-400mm

Success, Bert
04-05-2011, 09:57 AM   #4
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I'm surprised you're getting sharper results with that combination (any TC really, though that one is probably best of the bunch). That combo also makes it slower throughout the range, only adds 25mm and costs about double (assuming you can ever get your hands on the AF 1.7x TC).

I know you don't like the 120-400mm, but is not as bad as shooting through a pint glass as you might believe!

Anyway, to the OP, here is a long discussion in another thread on the forum; I posted some samples on the last page:

sigma-120-400mm-dg-os-hsm-pentax-anyone-tried-yet-7

Another thought occurred for the OP to chew on. The GX10 is showing its' age, it would be tough to use the 120-400mm on it since 800 ISO is probably the reasonable limit. perhaps it might be time to consider something like the Kr or K5, where ISO 3200 (or 6400) can be useable?


Last edited by pxpaulx; 04-05-2011 at 10:21 AM.
04-05-2011, 10:58 AM   #5
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QuoteOriginally posted by pxpaulx Quote
I'm surprised you're getting sharper results with that combination (any TC really, though that one is probably best of the bunch). That combo also makes it slower throughout the range, only adds 25mm and costs about double (assuming you can ever get your hands on the AF 1.7x TC).

I know you don't like the 120-400mm, but is not as bad as shooting through a pint glass as you might believe!
Maybe I'm just a little frustrated by the fact that there is no good 400mm alternative for Pentax right now.
I was determined to get a 120-400mm and got real disappointed by the results of a model I could try at the Kamera-Express store on my K-7 some time ago.
It was too soft. So I had to spend much more money on the DA* 60-250mm.

Sorry that I might seem a little edgy on the 120-400mm.
Sigma does make some very good lenses though, like the 17-50mm f 2.8.

No, it is not as bad as shooting through a pint glass... But still. I use that stuff while travelling. Don't have a second chance to do them over again, so it must be as good as it gets...

I found a second hand Pentax 1.7 AF for 25 in a small Amsterdam shop.
With that thing I could make a series of test shots with a 60-250mm.
I bought the lens the day after, after having a good look of the results at home.

I think it is a shame Pentax does not provide for that market.
Are you listening Hoya?!

As far as I can tell (from closely monitoring this forum section) it seems that the new 50-500mm Bigma model is the next best choice for 300+ mm.
However, the DA* 300mm seems still the sharpest.

- Bert
04-05-2011, 01:46 PM   #6
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You stole that TC, admit it!!!!

You're right about the competition - if you want something long, Sigma is it, unless you've got the bucks to go used and get one of the rare old Pentax lenses.

The new Bigma would probably be a better alternative as well (or perhaps the 150-500mm), but you sacrifice a small amount of speed, and in the case of the current Bigma, forget lightening your wallet, they'll take the wallet as well!
04-05-2011, 05:36 PM   #7
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QuoteOriginally posted by rayhf1485 Quote
I am trying out the Sigma lens at present, before I commit to buying. I would value some member comments from anyone who has done a comparison of these two lenses. I have read various reviews of both and, of course, the Pentax lens does get a high rating - and it should be better than the Sigma, given that it is more expensive, fixed focus etc. But how much better? Eye-popping better or what?

I have shot perhaps 200 pix over the last 24 hours. The light has been overcast to a greater or lesser degree, so 200-500 ISA has been set. I have used a monopod, tripod and hand held when there is a bit of sun. As expected, at 400mm, the images are a bit soft, but here's the rub, none of the images have the 'wow' factor that I am looking for over any of the focal lengths. I have shot wide open, but I have concentrated on the f8-f11 range, as recommended in all the reviews. I can't say there is anything wrong with the lens - CA seems well controlled and even the edge sharpness is tolerable and there doesn't seem to be any marked back/front focus issues. The lens is OK, but it still seems expensive for something that is 'just OK'!

I like to shoot a bit of wildlife, landscape and anything else that takes my eye. I want longer reach than 200mm and would prefer zoom, but there really is nothing to compete with the Sigma's versatility. However, I would pay up for the Pentax 300mm and forego the zoom versatility if I can get that 'wow' factor. The camera is a Samsung GX10 (10mp).


I would really like to hear your opinions!

Thanks

Ray
Ray, I cannot give you a direct comparison of these two lenses. However if you want to achieve the “wow factor” in your photo’s, you can do so with most glass if you shoot at its’ optimum aperture per focal length, in good light at low iso, with the correct technique; everything beyond that becomes degrees of compromise. The best glass will allow you a much bigger window of opportunity. Trying on your shoes I would look at the DA 55-300 as it seems to be the best general purpose zoom available – which is always good to have regardless. If I needed more performance a newer body and or long prime would be my next move (Hands shoes back). Lens buying it’s never an easy decision, so I hope something here helps, good luck.
04-05-2011, 11:12 PM   #8
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Thanks everyone for your replies - really helpful. I have been able to get a 60-250 DA* on apro to compare with the Sigma and so far the Pentax lens is much sharper than the Sigma. On the first series of test shots (indoors to get some better light!), I found I could pull up a shot taken at 250mm to the size of one taken at 400mm on the Sigma with sharper results. The other advantage is the fixed f4 max aperture, of course. Downside - no OS, so I have to rely on the Samsung in-camera OS and cost, of course.

Pxpaulx, you are right about the GX-10. I doubt if the extra pixels would make much difference, but the better dynamic range, high ISO and better burst rate and AF would certainly be better. Enough to make you wish you had the simplicity of film, when the improvements mostly came from better film, rather than massive leaps in technology and without the huge cost of upgrades. But with digital now able to outperform film, that's the price we have to pay!

Talking to a large retailer here in the UK, they have sent all their K-5 stock back to Pentax because of the stain issue and apparently the K-5 is now selling only slowly. I don't know how much truth there is in this, but this saga must have dented Pentax's credibility. Reading some of the K-5 posts, I get the impression (possibly incorrect) that the camera has it's fair share of technical issues - is that fair? If so, Pentax will need to get the price down fast (hopefully!!)

Thanks again.

Ray

04-06-2011, 05:31 AM   #9
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I don't believe that statement about the K5 is true at all. Retailers who have store fronts tend to push the big marketing brands, as they usually accompany the marketing with larger commissions to the dealer. Pentax simply doesn't do that, and generally pays the price at retailers - not only in terms of not getting the sales push, but often times directly put down by salespeople who want to sell the camera they'll get the most money from.

The stain issue has been addressed, other technical issues as well via the recent firmware. If you took one for a test drive, you'd not want to give it back, bottom line.
04-07-2011, 12:32 PM   #10
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I thought I would add a postscript to my original post. In the event, I have decided to buy the Pentax lens after a very detailed look at the results from both. Frankly there is not the huge difference in the performance of these two zooms that I was expecting and I think that is more of a testament for the Sigma, especially when the zoom range and on-board optical stabilisation is taken into account – and not forgetting the substantial price difference. The Pentax certainly has a bit more snap as well as the advantage of the fixed f4 maximum aperture, but what really swayed the decision was the more usable zoom range of the Pentax and the lighter weight and small dimensional is which make it a better walkabout proposition. I didn't find the 400 of the Sigma as useful as I thought it would be and I did find that the Pentax lens output can be enlarged to give just as good results, if not a little better.

All in all, there was an interesting exercise. I certainly wouldn't put any one of the Sigma if they are really looking for the longer reach. One big plus point for the Sigma is the OS, which I found more effective than the in-camera system of the Samsung GX10.

Thanks for your views.

Ray
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