[HanSch]

Hello all,

I'm the happy owner of a Sigma APO 100-300mm F4 EX DG zoom with matching 1.4x TC. This is an excellent lens, with only one drawback: the lens is not supported in DxO PL5. I don't need the geometrical corrections, or the CA/fringing corrections. They are small and can easily be done, if necessary, in another appication. But the "lens sharpness" option in PL5 is very valuable, as I experienced with my Pentax 16-45, 55-300 and Sigma 17-70 and 70mm Macro lenses (which are all supported). The "lens sharpness" correction in PL5 provides halo-free sharpening and is hard to beat with other algorithms.
The Pentax 150-450mm offers a similar range as the Sigma with 1.4TC, and with similar max. aperture. The 150-450mm is supported in PL5.

Are there any Pentaxians that had the opportunity to compare these 2 lenses one-to-one? The IQ of the Sigma decreases a bit, inevitably, with the use of the TC. I would like to know if the Pentax is better in the 300-450mm range, and I want to make sure that I don't loose IQ in the 150-300mm range. The camera is a K3 Mk.iii.

[biz-engineer]

would like to know if the Pentax is better in the 300-450mm range, and I want to make sure that I don't loose IQ in the 150-300mm range.

I can't tell about the sigma. I can tell the copy of dfa150-450 is sharp up to 400mm. It's sharp comparable to the 300 f4 at 300mm. Sharpness drops from 400mm to 450mm, such that wide open a 10% crop at 400mm gives as much detail as no crop at 450mm.

[gatorguy]

I can't tell about the sigma. I can tell the copy of dfa150-450 is sharp up to 400mm. It's sharp comparable to the 300 f4 at 300mm. Sharpness drops from 400mm to 450mm, such that wide open a 10% crop at 400mm gives as much detail as no crop at 450mm.

I hadn't noticed the 10% drop in sharpness.

I've got some images still to process from this past weekend, many at 450, I know at last a few at 400 (because of framing) and several from 150 and up. I'll see if I can tell a difference. I'll guess not unless pixel-peeping as it hasn't yet been obvious in the first 1000+ shots I've taken with it.

[jslifoaw]

I find mine is fully usable up to 450mm even wide open. The biggest hurdles to good shots (composition and lighting aside) are hand shake (IBIS isn’t as good at long focal lengths), shutter shock (makes shots slightly blurry even at very fast shutter speeds) which disappears using EFCS at the cost of slow readout, and atmospheric distortion caused by varying ambient temperatures.

[biz-engineer]

I hadn't noticed the 10% drop in sharpness.

Just go to PF review and compare 300mm f5.6 corner to 450 f5.6 corner. HD Pentax-D FA 150-450mm F4.5-5.6 Review - Sharpness | PentaxForums.com Reviews
Sharpness between 300 and 400 is pretty much constant, the drop of resolution is between 400 and 450mm (and this makes sense, most zooms have a tradeoff, either at the short end or at the long end).

[gatorguy]

Just go to PF review and compare 300mm f5.6 corner to 450 f5.6 corner. HD Pentax-D FA 150-450mm F4.5-5.6 Review - Sharpness | PentaxForums.com Reviews
Sharpness between 300 and 400 is pretty much constant, the drop of resolution is between 400 and 450mm (and this makes sense, most zooms have a tradeoff, either at the short end or at the long end).

I understand someone measured something on their copy of a lens. I've not seen a 10% sharpness dropoff at 450mm. I'll assume you have seen center sharpness suffer on your 150-450, was it at all apertures, or did you only read about that 10% somewhere? I didn't see that claim in the PF article.

Reading the link you offered the real world performance was better than what the test bench was showing, something the reviewer anticipated. To quote:" The center is excellent at all focal lengths, and more importantly wide open. For the most common use case (a subject isolated from the background) the sharpness figures of the lens are ideal."

I shoot wildlife with mine, and since at 450 it's quite likely the resulting image is cropped anyway, a fall-off in some corner is a non-issue.

[nixxo2002]

I hadn't noticed the 10% drop in sharpness.

I've got some images still to process from this past weekend, many at 450, I know at last a few at 400 (because of framing) and several from 150 and up. I'll see if I can tell a difference. I'll guess not unless pixel-peeping as it hasn't yet been obvious in the first 1000+ shots I've taken with it.

i had the lens for a past 7 years , and it didn't drop sharpness at 450 . i shoot with K3 ii , K3 iii , KP , and k1 II .

[Paul the Sunman]

My 150-450 is stellar throughout the zoom range. It gets plenty of work at 450mm.

[clackers]

So these are the official MTF curves for the DFA150-450.

For a non-decentered specimen it's actually sharper at 450 than 150, with less field curvature, but the edges might get some harshness to the bokeh or other aberrations at that longest length - look at that MTF30 divergence.

I've also attached an MTF from Dyxum.com of the Sony A mount version of the Sigma 100-300 for comparison. Again, the edges, not the centre, are the problem. To compare with the Pentax at that length, you'd have to interpolate the top two graphs.

[biz-engineer]

i had the lens for a past 7 years , and it didn't drop sharpness at 450

Mine is less sharp at 450 than it is at 400. If your DFA 150-450 is as sharp at 450mm as it is at 400mm, doesn't this make my DFA 150-450 sharper?

[gatorguy]

Mine is less sharp at 450 than it is at 400. If your DFA 150-450 is as sharp at 450mm as it is at 400mm, doesn't this make my DFA 150-450 sharper?

Nonsensical. Your copy may not be as good as the OP's. Or mine. Or several others who have commented in this discussion, not finding that 10% performance hit you're claiming at 450.

There is some variance in production runs as you yourself have pointed out before. If you're getting less than stellar results it may just be your copy of it. It's been noted before that the 150-450 is pretty unusual for a long tele, performing as well at the long end as it is in the middle. My 170-500 Sigma certainly doesn't with an obvious falloff from 450-500, and that is the more common tendency in telezooms that the 150-450 designers seem to have avoided.

[HanSch]

So these are the official MTF curves for the DFA150-450.

For a non-decentered specimen it's actually sharper at 450 than 150, with less field curvature, but the edges might get some harshness to the bokeh or other aberrations at that longest length - look at that MTF30 divergence.

I've also attached an MTF from Dyxum.com of the Sony A mount version of the Sigma 100-300 for comparison. Again, the edges, not the centre, are the problem. To compare with the Pentax at that length, you'd have to interpolate the top two graphs.

Thanks, these are very useful graphs. According to the MTF curves the 2 lenses are more or less comparable on this aspect.

[clackers]

Thanks, these are very useful graphs. According to the MTF curves the 2 lenses are more or less comparable on this aspect.

Yes, the Sigma's good, but it only goes to 300mm, which is what you would get with the DA55-300.

You can see the DA is pretty good at 300 itself, but it's not full frame, and it's already f5.8. You could put a 1.4 TC on the Sigma and still be within the specs of the autofocus system.

[biz-engineer]

Nonsensical. Your copy may not be as good as the OP's. Or mine. Or several others who have commented in this discussion, not finding that 10% performance hit you're claiming at 450.

That's fine. I was just sharing my practical experience as owner of the DFA150-450 and DA*300 (that I used for birding and wildlife photography with and without TC). When I posted my comment I didn't have any particular agenda in mind.

[HanSch]

Yes, the Sigma's good, but it only goes to 300mm, which is what you would get with the DA55-300.

You can see the DA is pretty good at 300 itself, but it's not full frame, and it's already f5.8. You could put a 1.4 TC on the Sigma and still be within the specs of the autofocus system.

I have the 55-300mm as well, the first edition, non-WR. It is a very convenient lens for traveling and hiking, light and with reasonable IQ. But the IQ is no match for the Sigma 100-300mm. Not surprising, taking the prices into account. And the AF is a very different story. AF of the 55-300 is accurate (after micro-adjustment), but slow and a lot less accurate for moving subjects. Practically not usable for e.g. birds in flight.
I use the Sigma 100-300mm with the matching TC1.4, and with a Soligor TC2. IQ suffers a bit of course, but AF stays pretty reliable but slower. An advantage of the Pentax 150-450mm could be, that the focus throw is very long. I like to focus manually if possible and the Sigma has a very short throw, making MF a pain. The focus ring is comfortably wide, but you touch it and the focus is gone.
If I can compare the Pentax 150-450 with the Sigma 1:1 and decide to buy the Pentax I will probably sell the Sigma 100-300 to ease the pain in the purse.