[pxpaulx]

I tried this sigma with k-7. The OS works when SR is turned off. The lens is not bad, however stiff zoom and average IQ made me buy sigma 70-200mm non OS

The few times I've been testing my OS version, I forgot to turn off the in-body IS and didn't notice any real negative affect (could be random of course).

[normhead]

Here are another few shots from todays hike, some of them at full reach. The first one is close to 1-1 for the pixel peepers. It's also probably 75 meters away.

[jpzk]

So, the "official" Pentax Forums announcement states that this lens is OS after all, and reading from the B&H Photo ad, that seems to be the case.
Sigma 120-400mm f/4.5-5.6 DG APO OS HSM Autofocus Zoom 72A109

Is this REALLY a confirmation that the lens is OS for Pentax?


JP

[jpzk]

Here are another few shots from todays hike, some of them at full reach. The first one is close to 1-1 for the pixel peepers. It's also probably 75 meters away.

Norm,

This first shot (of two) of the birds on water ... did you have any SR or OS turned on at all?
I am asking because it does show a hand held situation at low shutter speed or/and perhaps with the SR/OS off?
What caused it to show blur?

JP

[pxpaulx]

So, the "official" Pentax Forums announcement states that this lens is OS after all, and reading from the B&H Photo ad, that seems to be the case.
Sigma 120-400mm f/4.5-5.6 DG APO OS HSM Autofocus Zoom 72A109

Is this REALLY a confirmation that the lens is OS for Pentax?


JP

How many times do I have to tell you, mine is OS, and yes its a K mount!

The 47th Street Photo salesperson I spoke with (while in the process of getting my OS version) stated that his Sigma rep indicated the non-OS versions are being discontinued, and that only the OS version will be sold once the old stock clears.

[normhead]

As I stated above, I got the non-OS, I returned it and got the OS version.

This first shot (of two) of the birds on water ... did you have any SR or OS turned on at all?

There is no shake reduction, but the lens is mounted on a tripod with a two second shutter delay so, it should be good. I checked to make sure the camera was set at infinity, and it was well over 125 feet, so it should have been. The only thing I can think is, I was shooting down river. There could be diffraction from varying humidity and temperature levels at different points on the river. That's my best guess. Kind of disturbing since I took the first lens back because it didn't focus well at infinity. I'll give it another try tomorrow.

[jpzk]

How many times do I have to tell you, mine is OS, and yes its a K mount!

The 47th Street Photo salesperson I spoke with (while in the process of getting my OS version) stated that his Sigma rep indicated the non-OS versions are being discontinued, and that only the OS version will be sold once the old stock clears.

You may well have to tell me everyday until I get my hands on one and try it!

Seriously, with all of the contradictory posts as to whether this lens comes or not with OS (for Pentax), you have to admit that it does become confusing.

On the other hand, I'll take your version of the facts, which is obviously credible, since you do own such a lens.

Thanks for the up to date information!

Cheers.

JP

[jpzk]

As I stated above, I got the non-OS, I returned it and got the OS version.



There is no shake reduction, but the lens is mounted on a tripod with a two second shutter delay so, it should be good. I checked to make sure the camera was set at infinity, and it was well over 125 feet, so it should have been. The only thing I can think is, I was shooting down river. There could be diffraction from varying humidity and temperature levels at different points on the river. That's my best guess. Kind of disturbing since I took the first lens back because it didn't focus well at infinity. I'll give it another try tomorrow.

Yes, that could account for the "softness" ... as a matter of fact, [and it never donned on me until you explained that you were at least 125 feet away and across a fair size body of water], this happened to me quite a few times.
How far away were you for the second shot ... with the running water and ice? This one is actually very sharp.

Thanks for the info.

JP

[normhead]

How far away were you for the second shot ... with the running water and ice? This one is actually very sharp.

I'm guessing that the second shot was between 75 and 100 feet.

[Stringmike]

As you all know, I was one of the skeptics as I owned the earlier HSM/non-OS version. The confusion arose because Pentax and Sony versions of this previous lens were not OS, but many dealers listed them wrongly. When the new version turned up, dealers still had stocks of both and non-OS ones were shipped until the old stock was gone.

It would probably be useful when ordering in the next month or so to double-check that what you're getting is the new OS version and not old stock.

Mike

[pxpaulx]

It is also nice to see that the pricing of the OS version is the same (At least for now). As Stringmike said, for the next month or 2 if you are ordering the lens, it would be a smart move to make some sort of direct contact with the seller to ensure you get what you pay for (though I am sure most would rectify the situation, it is best to avoid a possible return/exchange from the start!).

I got mine from 47th st photo through their ebay listing - note they have a best offer option - I offered about 8% off msrp and it was accepted. They were prompt and helpful through the whole process of verifying it was the OS version, though they still had non-OS stock the sales rep hand picked out the new OS version for me to make sure I received the correct lens. The lens is a US version with full warranty from them as well (yes, this paragraph is a recommendation!).

[bymy141]

I've been studying this lens last year (non OS version) and did not buy it because of the test results of various websites.

For example, this is what slrgear has to say about the lens:
++++++++++++++++++++++++++++++++++++++++++++
Sharpness
The 120-400mm is a fairly sharp lens, but its performance is optimized for the wider range of its focal length spectrum. As you zoom in towards the 400mm range, image sharpness degrades significantly. Optimal image sharpness was achieved at either 120mm and ƒ/5.6, or 150mm and ƒ/8.

Wide open and wide-angle (120mm, ƒ/4.5) image sharpness is quite good, with test results showing 1.5 blur units across the frame. Stopping down to ƒ/5.6 improves central sharpness to 1 unit, but there is still some very slight corner softening. Diffraction limiting seems to set in at ƒ/11, but image quality never gets so bad, reaching 2.5 blur units at ƒ/22. Results at 150mm are almost the same, just a tad less sharp.

However, at 200mm and above, image sharpness starts to worsen. Our sample copy of the lens also showed some centering issues at this focal length. Sharpness showed results of between 1-2 blur units in a very small central region, while corner softness reached 4.5 blur units; as the lens is stopped down, quality improves dramatically at ƒ/8 and ƒ/11 (1 blur unit centrally, 2-3 units in the corners) and the image is generally soft at ƒ/25 (3 blur units).

Between 300 and 400mm, performance when used wide open (ƒ/5.6) is nothing to write home about - very uneven and soft (3-5 blur units at 300mm, and 5-8 units at 400mm). Stopping down to ƒ/8 or ƒ/11 is necessary to get any kind of sharpness out of the lens at this focal length. Interestingly, image sharpness is better at ƒ/22-29 than when used wide open at these focal lengths.

Full-frame performance is similar across all focal lengths and apertures, although corner softness is generally more of a factor throughout. We do note some interesting ''blips'' of extreme corner softness, particularly at 250mm. Optimum performance on a full-frame body is 120mm or 150mm at ƒ/8.

Chromatic Aberration
The 120-400mm ƒ/4.5-5.6 tolerates chromatic aberration very well, better at the wider end of its focal length range. At 120mm the lens shows less than 2/100ths of a percent of frame height CA generally, and less than 3/100ths in the corners. This is very good performance. As the lens is zoomed in and stopped down CA tolerance degrades slightly, but never objectionably. Even at 400mm and ƒ/5.6, performance is still good at less than 3/100ths generally and 4/100ths in the corners. CA performance is as good or better on a full-frame body.

Shading (''Vignetting'')
Corner shading isn't an issue with the 120-400mm mounted on a subframe camera body; the worst-case scenario is noted when using the lens wide open (ƒ/4.5-5.6), and even then we note the corners only a quarter-stop darker than the center. At any other apertures, corner darkening is insignificant.
++++++++++++++++++++++++++++++++++++++++++++

Also, you can play and see the results for yourself using this script:
120-400mm interactive blur chart

I guess results can be good at the long end of the lens if there is a lot of light.
For instance a picture taken in Arizona with full daylight will make is possible to shoot at f11 or so, reducing most of the lens its sharpness issues to acceptable levels.

I guess, as soon as you've been spoiled by the much better DA* results, this lens is not an option anymore.
I'd go for a DA*60-250mm, or even better a DA*300mm and crop the results. Todays 15 or 16 Mp sensors give you some room for that.

- Bert

[Frogfish]

bymy141 - thanks for posting that. This lens was creeping higher and higher on my wish list and challenging my ' 60-250' or *300 thought processes. Now I've seen those 3-5 blur units at 300 it's gone !

[pxpaulx]

Bert,

I am sure quite a few of us have read that review - some of it reads as though the 120-400mm might in fact just be a pint glass shrouded in a lens casing, when that is not really the case. There are also some real-world user reviews out there that appear to provide useable results!

Also, when it comes to Sigma you definitely can't judge based on a single lens review - their QC can be pretty poor at times.

[jpzk]

I'm guessing that the second shot was between 75 and 100 feet.

That is good. Still sharp and across water.

In spite of the review provided below (post by bymy141) which states that the lens is unsharp at longer focal lengths, I do think that it is still "an option" as opposed to what is said.
I will be looking for more reviews before I make the final decision though.

Thanks for the info.

JP