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View Poll Results: Sigma 120-300mm F2.8 or Pentax FA* 300mm F2.8?
Sigma 120-300mm F2.8 APO EX DG OS HSM 3257.14%
Pentax FA* 300mm F2.8 2442.86%
Voters: 56. You may not vote on this poll

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03-05-2011, 03:12 PM   #1
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Sigma 120-300mm F2.8 or Pentax FA* 300mm F2.8

The Sigma 120-300mm F2.8 APO EX DG OS HSM with weather seals is due for our mount in May for $3200

The Pentax FA* 300mm F2.8 is legendary. It's cost used when you can find it tends to be $3100-$3500.

The pros of the Sigma are:
New
4 year warranty
it's predecessor without OS is said to be sharper than the Sigma 300mm/2.8 prime
Service is available
It's got zoom to it instead of being restricted to 300mm
105mm thread
The non-pentax hsm predecessors could use the 1.4x and 2.0x TCs in those mounts with autofocus.

However the Pentax lens is reported to be the best telephoto of all time.
Service for this lens may not be possible or may require shipment to Japan,

Which lens should I wait for? Which lens are you waiting for?

03-05-2011, 04:04 PM   #2
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I have a F* 300mm f4.5, A* 300mm f2.8 and Sigma 100-300mm f4.

Once the 120-300mm Sigma is released in Pentax mount (and provided it is up to spec) I will sell all 3. (and possibly the 60-250mm as well).
03-05-2011, 06:04 PM   #3
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5 votes for the FA*. I'd love to hear some counterpoints for the FA* over the Sigma.
03-05-2011, 06:23 PM   #4
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The Sigma is a truly awkward and heavy 120/2.8 lens

03-05-2011, 07:10 PM   #5
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A zoom lens will never truly match a prime. Even with todays advanced optical designs when zoom lenses take one step forward in quality, primes take two*.

I have actually used the sigma 120-300mm f/2.8 APO EX DG on my Nikon D3s. And from my experience the lens puts in a decent performance the only area I am disappointed is flare tolerance which is where the FA*300mm f/2.8 will beat it hands down. Resolution on the D3s is a bit lacking at the corners at 300mm f/2.8 though stop it down to f/4 and the lens improves substantially producing crisp areas of focus with very good OOF rendering, the sweet spot with this lens on the D3 is f/5.6. Vignetting can be visible at 120mm f/2.8, but the main selling point is that the Sigma 120-300mm f/2.8 works very well with teleconverters, though be warned the AF can be a bit twitchy.It also has no filter drawer and the lens hood is the same plastic fantastic design that they use with the 100-300mm f/4 - personally I would expect a built in metal hood- especially at this price point.


* There are exceptions E.G The image quality from the Nikkor 14-24mm f/2.8G beats the Zeiss 18mm f/3.5 at all apertures - but of course the zoom nikkor isn't anywhere near as compact as the Zeiss lens, and it also has a rather nasty prismatic flare characteristic.

Last edited by Digitalis; 03-05-2011 at 07:23 PM.
03-05-2011, 09:13 PM   #6
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I think all the Sigma 120-300mm F2.8 APO EX DG OS HSM voters really just want one of the lenses MikeP will sell when he gets his!
03-05-2011, 10:21 PM   #7
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QuoteQuote:
However the Pentax lens is reported to be the best telephoto of all time.
Service for this lens may not be possible or may require shipment to Japan,
I don't know where that came from, but the new one I had was not sharp at all at distances and pentax wouldn't adjust it. So I voted for the sigma. I'm not sure if the sigma TC's work with the pentax sdm though. I wound up getting a different mount for a 300mm f2.8. I guess it was good that my FA*300 f2.8 wasn't good as it pushed me to try other bodies that are more suited to wildlife.

Here is a crop (not even 100%) from my FA* at f5.6 and this is about the best it would do. Yes it is as focused as it could get and not motion blur.
03-06-2011, 10:20 AM   #8
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QuoteOriginally posted by borno Quote
I don't know where that came from, but the new one I had was not sharp at all at distances and pentax wouldn't adjust it.
That's part of my concern with picking up an FA* of this magnitude. It seems as though it's like buying a car that you can't get parts for.

03-06-2011, 11:58 AM   #9
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QuoteOriginally posted by Clinton Quote
That's part of my concern with picking up an FA* of this magnitude. It seems as though it's like buying a car that you can't get parts for.
I guess I should have checked it out with a laptop instead of just my camera when I got it. I had never heard of any Pentax 300mm primes as being not up to par and assumed it was fine, and I'm sure it is rare but can happen. I was also mistaken by assuming it would be adjusted by the manufacturer. They finally told me it was designed for film and some older designs may not be optimal on a DSLR. That is really what got me steamed.

As an aside, I saw a tamron 300mm f2.8 AF in the adorama used section in K mount.
03-06-2011, 02:01 PM   #10
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QuoteOriginally posted by borno Quote
As an aside, I saw a tamron 300mm f2.8 AF in the adorama used section in K mount.
No matched AF teleconverters though...
03-06-2011, 04:25 PM   #11
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QuoteOriginally posted by Digitalis Quote
A zoom lens will never truly match a prime.
Hmmm, Isn't it agreed that the Sigma @300mm is sharper than the FA300 @ 300mm?

QuoteQuote:
I am disappointed is flare tolerance which is where the FA*300mm f/2.8 will beat it hands down.
I doubt that the newer version with it's special 2xFLD elements would suffer from this issue in the same fashion. ?

I'm most interested in knowing how good (sharp) the new Sigma is @ 300mm F/2.8 & F/4.
03-06-2011, 05:59 PM   #12
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QuoteOriginally posted by Freak Quote
I doubt that the newer version with it's special 2xFLD elements would suffer from this issue in the same fashion. ?
you can use whatever glass you want in a lens, but if the lenses aren't coated (and we all know sigma's lens coatings leave a lot to be desired) the lens's performance will be impacted. Under field conditions I have suffered from flare that completely wrecked some images from my 100-300mm f/4 APO EX DG - and before you ask, yes I did have the lens hood on, and I don't use "protective" filters.

QuoteOriginally posted by Freak Quote
Isn't it agreed that the Sigma @300mm is sharper than the FA300 @ 300mm
@ f/2.8 the prime will be superior to the zoom. Compared to my Nikkor AF-S 300mm f/2.8G ED VR the sigma 120-300mm f/2.8 APO EX zoom the image quality is lacking at f/2.8 - at f/8 there is little difference between the prime from the zoom lens. The optimum aperture of your typical 300mm f/2.8 lens is typically one stop down from widest aperture, for the sigma zoom, the optimum is reached at two stops - so the prime has a one stop advantage. And one stop can be the difference between getting the shot -and not.

Last edited by Digitalis; 03-06-2011 at 06:05 PM.
03-06-2011, 08:23 PM   #13
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QuoteOriginally posted by Digitalis Quote
you can use whatever glass you want in a lens, but if the lenses aren't coated (and we all know sigma's lens coatings leave a lot to be desired
This was my point, Pentax's coatings are known to be lacking for CA in particular.

Sigma claims it's FLD elements are class leading, and recent reviews of the FLD type lenses back up their claim that it's much improved flare/ghosting and CA. So I would be surprised if the newer Sigma didn't perform better than the older FA in this regards to flare etc..

But i guess we will have to start waiting for the reviews, before we know for sure.


QuoteQuote:
@ f/2.8 the prime will be superior to the zoom.
Fair enough most of the reviews impressions seems to paint it the opposite picture on these lenses. While i agree in principal, just because it's a prime, doesn't automatically make it better than a zoom IMO. It's most often the case though.

I have not used either in this case, but i will be purchasing the 120-300 when it's released.
03-06-2011, 09:03 PM   #14
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QuoteOriginally posted by Freak Quote
Pentax's coatings are known to be lacking for CA in particula
lens coatings have a very indirect effect on chromatic aberration. It is the overall optical design that is responsible for this characteristic, though coatings increase the image contrast by eliminating internal reflections, and this increase in image contrast has the effect of making aberrations look worse.

The best way to eliminate Chromatic aberration in wide angle lenses is make use of high grade ED (extra dispersion) and LD (low dispersion) glass types to shift the colour spectra so the three primary colours focus at exactly the same plane. It is when these colours aren't perfectly focused, and how far they are misfocused is what causes the appearance of chromatic aberration .

Lenses over 100mm typically employ apochromatic designs to get red,green and blue light to focus at exactly the same plane, however apochromat designs are nearly impossible to use on focal lengths shorter than 100mm because the lens elements would have to be aligned with perfect microscopic precision - and with alignment tolerances that small for mass produced products(providing quality control uses similar tolerances) would cause lens prices to go stratospheric.

Last edited by Digitalis; 03-06-2011 at 09:10 PM.
03-06-2011, 10:48 PM   #15
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QuoteOriginally posted by Digitalis Quote
Even with todays advanced optical designs when zoom lenses take one step forward in quality, primes take two*.
It seems to me that many prime designs are quite old and hard to improve, whereas zoom lenses improved in leaps and bounds since the 60's. The new Nikon 85/1.4, e.g., doesn't have a new optical formula. Many would describe the improvements of the DA* 55 over the FA 50/1.4 (very old design) not nearly as dramatic as between old and new zoom lenses. No one would have even begun to compare a zoom to a prime in the 60's.

QuoteOriginally posted by Digitalis Quote
you can use whatever glass you want in a lens, but if the lenses aren't coated (and we all know sigma's lens coatings leave a lot to be desired) the lens's performance will be impacted.
I didn't know that Sigma coatings leave a lot to be desired. I bet it escaped thousands of others as well. What I do know is that the coatings of all older Pentax lenses I tried a pretty horrible in comparison to the coatings on my Tamron and Sigma lenses. They create an odd green tinge that is hard to correct in PP, as if some colours were removed. Really bad for skin tones and foliage. I had access to a K 50/1.2 for months and only used it briefly on two occasions because of the ugly colours it produced. If my interest had been in B&W then it would have been fine. Other older Pentax lenses I tried (e.g., M135/3.5, M 85/2, K55/1.8) show a similar effect, not as strong as the 50/1.2 I had but still.

From my experience modern Sigma coatings blow the old SMC stuff out of the water. Way more contrast and more natural colours.

Has anyone ever looked into the relationship between Pentax losing their advantage regarding lens coatings (the others caught up, you know) and losing its position as one of the top lens/camera manufacturers? Surely Pentax lost a lot of ground being late to the digital game but I wouldn't be surprised if their demise had some relationship to their lens coatings not being a unique selling proposition anymore.

BTW, I understand once lens coatings become decent their effect on lens flare are not significant. I believe all modern coatings from any major manufacturer are just fine regarding lens flare and the latter is dominated by optical design and the internal built of the lens.

Last edited by Class A; 03-06-2011 at 10:57 PM.
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