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06-22-2020, 08:21 AM - 4 Likes   #61
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@BruceBanner ...

My observations about the DA55-300PLM - DA TC 1.4x - combo:
  • The performance of the lens - TC - combo depends strongly on the shooting conditions.
  • At near to mid distances the lens delivers really great.
  • At long subject distances and 420mm it works ok. But sharpness of the images is not great but ok. So I'm not always satisfied.

I think there are at least two reasons for the latter:
  • the AF seems not always accurate at the long end depending on the shooting conditions. But maybe it's also my problem?! Or the following aspect kicks in additionally .
  • lightweight and not massive build transports shutter vibrations much more than on the DFA150-450. I used a tripod and it didn't get much better.

I'd say you own a DA55-300PLM - a great lens without doubt. Just get a DA TC1.4x - it's not that expensive and it's also great and you can use it with other lenses. Then you can test in every way and under conditions that fit exactly your purpose.

If IQ isn't good enough for you, just sell the DA TC and buy the DFA150-450. But maybe you're pockets are empty until then because you bought the DFA21 Ltd.

Some images taken with DA TC1.4x and DA55-300PLM ...






























Last edited by acoufap; 06-22-2020 at 10:25 AM.
06-22-2020, 10:08 AM   #62
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I have both the PLM and the 150-450 to go with my KP. The KP/PLM combo is my grab and go/travel/hiking option. And it works great for that. It's gone on 15 mile hikes through the Costa Rican rainforest, which was a very challenging shooting environment.
The 150-450 is significantly better IQ, plus significantly longer. But it's way larger and heavier. I wouldn't carry it for long hikes or walking around while travelling unless I was really sure I was going to use it and need it A LOT.

In both cases, I did not feel that the TC was enough better than cropping to justify using it. But others have different opinions on that topic.

The mountain goat picture attached was this weekend at 11500 ft in the Uinta mountains. Good lighting, but shooting up a slope at a target probably 250-300m away. The quail, on the other hand, was a quick shot in my backyard when i noticed it in the garden.
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06-22-2020, 02:27 PM   #63
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Thanks for those contributions.

Was a FF TC ever on the roadmap for Pentax? I could hold off prolly for a year or so if there was such a rumour...
06-22-2020, 02:35 PM - 1 Like   #64
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Suprise Visitor

I had a surprise visitor yesterday and went to grab the KP, Having been following this thread I had been trying the 55-300 plm with different settings and adapters including the 1.4x teleconverter. However I remembered that I had a 1.7x Sony VCL-DH1758 front teleconverter which I bought a while back but it was never very successful with the Fuji 50-230. So when I had a surprise visitor on the lawn it was the KP with 55-300 + the 1.7x Sony. Shot through double glazing with lens at 230mm giving 390mm at f8 the result impressed me greatly. I have since tested it out to 300mm/510mm and the results are excellent. The beauty of the front teleconverter being that you can still use the full aperture of the lens. The down side is that when the lens is set between 70mm and 100mm there is vignetting - but not at 55mm or above 100mm

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06-22-2020, 05:18 PM - 2 Likes   #65
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QuoteOriginally posted by BruceBanner Quote
So this is the second time I have heard this, thanks for continuing to educate me. Can you expand on this at all? What does it really mean when we say 'autofocus is rated to f5.6'?
Have you ever used a split prism viewfinder? That's where you find a line on your subject and get the bottom half to line up with the top half by turning your focus dial, and that means it's in focus, when they coincide.

So, the analogy is to the PDAF module above the mirror box. That dedicated sensor has pixels in strips. As I understand it, they have to be long enough for good discrimination between their ends, and the aperture has to be wide enough to get a nice length of the subject under them. For DSLRs f5.6 is something the makers can cope with.

Mirrorless cameras like Sony, Fuji, Nikon and Canon have this tremendous problem, then. They lack a mirror = no dedicated focus module.

Beholder3 calculated IIRC something like 12 percent of the sensor pixels are affected by having to use on sensor PDAF. Because of Bayer, that's the strips themselves and the immediate surrounding ones.

The RAW file is manipulated to cover these blind spots, you get no say in it, copying and pasting like Content Aware in Photoshop. Artifacts like banding can arise as a result, MJKoski has been disgusted IIRC raising shadows at ISO 100 in the Canon RP RAW files.

Panasonic as a result, refuse to use PDAF, saying it affects mirrorless image quality. Fuji use it very sparingly, only one medium format camera has it, and Digilloyd complained: "The Fujifilm GFX100 cannot capture some shades of blue sky without visible pattern noise, due to the inclusion of its PDAF pixels. "

QuoteOriginally posted by BruceBanner Quote

1) Are we talking PDAF here or CDAF when it comes to this aperture AF limit?
PDAF. CDAF does not use the method of making two ends of a line coincide on paired pixels.

Note that it is important for you when you focus on your subject whether it is a vertical line or a horizontal line. If you compose off centre, the ones on the outside can only focus on horizontals. The ones in the centre can do either, they're 'cross' points. Pentax have historically been pretty good at providing those, which is not appreciated by many Pentaxians. The Canon 6D full frame camera had only one cross point, for instance.

QuoteOriginally posted by BruceBanner Quote
I always understood in PDAF the centre spot and spot directly above and below were 'rated to f2.8', I just took this to meaning they are better more accurate AF points to use, and that to use Spot AF mode (not centre point SEL spot) would actually even increase AF accuracy a little more. I never really thought about the other AF points in terms of f number accuracy.
No, in this case, we are talking about the *widest* aperture they're rated for, not the narrowest. So this means focusing an f1.4 lens is inherently hit and miss, because the focus point is really focussing at f2.8, not f1.4. On average, the focus plane will be the same, but because f2.8 has a greater depth of field there will be more variation acceptable to the sensor before calling it a match.


QuoteOriginally posted by BruceBanner Quote

3) If 5.6 is the maximum aperture for autofocus, then what is Pentax doing with the PLM 55-300 which has f6.3 as its minimum on the long end? What does that mean? Do we take it that Pentax are not the same as the others and have AF points rated higher than 5.6?
No, it's simply an inferior lens - I have one, by the way, and love it regardless. I also have a Sigma 150-500, guess what, also f6.3 at the long end, and never to be completely trusted.

There are mirror lenses that are f8. Ok, but they're manual focus. Just understand that focus confirmation can never be guaranteed to work on them, because that uses the PDAF module.

Sports photographers pay $10,000 for a 400mm f2.8 prime. One reason is they need all the AF points to work when tracking players. A wildlife photographer can aim for a $12000 600mm f4. They're likely to affect that with a TC, so 1.4 will give them f5.6.

QuoteOriginally posted by BruceBanner Quote
4) What does this mean when we use say a FA77 at f8? It's less accurate than using f2.8? Are we getting that depth of field trade off where AF accuracy is less but because focus plane is deeper the AF inaccuracies are harder to detect?
No, in taking a shot DSLRs go through a cycle. For the focus stage, they open up to the widest aperture anyway for increased accuracy. This is why I'm baffled to see anyone here suggesting to a member with a problem to troubleshoot by microadjusting at different apertures. Doesn't happen.



QuoteOriginally posted by BruceBanner Quote
It's been more of a gut feeling than anything else, but my experience with the PLM thus far feels like it is sharper at its wide open apertures
Unless the ISO climbs from stopping down, giving more grain, it's user error on your part, Bruce, I'm afraid to say. There is no lens of any brand that is not sharper closing it down a bit. The reason is you're progressively excluding the 'junk' light from the very edges of the elements, the good stuff without aberrations is directly in the centre, along the axis.

Last edited by clackers; 06-22-2020 at 05:41 PM.
06-22-2020, 05:45 PM   #66
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Note some of the problems with the limited size of a mirrorless' PDAF sensors here in this Sony A7 II review.:

"The Sony A7 II comes with an improved version of the hybrid autofocus system found on its predecessor, offering up to 30% faster autofocus performance. This hybrid AF system is a combination of phase and contrast detect AF, which allows for much quicker AF acquisition than only contrast detection, which is found on both Sony A7R and A7S. The difference in AF performance between the A7 series cameras is quite noticeable, particularly when shooting in good light – the A7 II acquires focus much faster in comparison with phase detection engaged. When light levels drop, the camera switches to phase detection, slowing down autofocus operations.

With a total of 117 phase detection AF points and 25 contrast detection points, the A7 II features a fairly complex AF system. But how much faster is the A7 II compared to the A7? In Single Focus mode (AF-S), it certainly feels a bit snappier than the A7. But it is still a somewhat mixed bag: in some situations, AF acquires very quickly and takes no time, while in other situations, the camera probes for focus first, as if it switches to contrast detect (with plenty of ambient light). Continuous AF certainly got a boost and the A7 II feels more like the A6000 (which is pretty decent for continuous AF), but not as good as OM-D E-M1 and certainly not anywhere close to what a full-frame DSLR can do. If you are into photographing fast-moving subjects, the A7 II will disappoint you, so you will be much better off with a DSLR instead."

... https://photographylife.com/reviews/sony-a7-ii/4
06-22-2020, 08:41 PM   #67
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QuoteOriginally posted by clackers Quote
Have you ever used a split prism viewfinder? That's where you find a line on your subject and get the bottom half to line up with the top half by turning your focus dial, and that means it's in focus, when they coincide.

So, the analogy is to the PDAF module above the mirror box. That dedicated sensor has pixels in strips. As I understand it, they have to be long enough for good discrimination between their ends, and the aperture has to be wide enough to get a nice length of the subject under them. For DSLRs f5.6 is something the makers can cope with.

Mirrorless cameras like Sony, Fuji, Nikon and Canon have this tremendous problem, then. They lack a mirror = no dedicated focus module.

Beholder3 calculated IIRC something like 12 percent of the sensor pixels are affected by having to use on sensor PDAF. Because of Bayer, that's the strips themselves and the immediate surrounding ones.

The RAW file is manipulated to cover these blind spots, you get no say in it, copying and pasting like Content Aware in Photoshop. Artifacts like banding can arise as a result, MJKoski has been disgusted IIRC raising shadows at ISO 100 in the Canon RP RAW files.

Panasonic as a result, refuse to use PDAF, saying it affects mirrorless image quality. Fuji use it very sparingly, only one medium format camera has it, and Digilloyd complained: "The Fujifilm GFX100 cannot capture some shades of blue sky without visible pattern noise, due to the inclusion of its PDAF pixels. "



PDAF. CDAF does not use the method of making two ends of a line coincide on paired pixels.

Note that it is important for you when you focus on your subject whether it is a vertical line or a horizontal line. If you compose off centre, the ones on the outside can only focus on horizontals. The ones in the centre can do either, they're 'cross' points. Pentax have historically been pretty good at providing those, which is not appreciated by many Pentaxians. The Canon 6D full frame camera had only one cross point, for instance.



No, in this case, we are talking about the *widest* aperture they're rated for, not the narrowest. So this means focusing an f1.4 lens is inherently hit and miss, because the focus point is really focussing at f2.8, not f1.4. On average, the focus plane will be the same, but because f2.8 has a greater depth of field there will be more variation acceptable to the sensor before calling it a match.




No, it's simply an inferior lens - I have one, by the way, and love it regardless. I also have a Sigma 150-500, guess what, also f6.3 at the long end, and never to be completely trusted.

There are mirror lenses that are f8. Ok, but they're manual focus. Just understand that focus confirmation can never be guaranteed to work on them, because that uses the PDAF module.

Sports photographers pay $10,000 for a 400mm f2.8 prime. One reason is they need all the AF points to work when tracking players. A wildlife photographer can aim for a $12000 600mm f4. They're likely to affect that with a TC, so 1.4 will give them f5.6.



No, in taking a shot DSLRs go through a cycle. For the focus stage, they open up to the widest aperture anyway for increased accuracy. This is why I'm baffled to see anyone here suggesting to a member with a problem to troubleshoot by microadjusting at different apertures. Doesn't happen.





Unless the ISO climbs from stopping down, giving more grain, it's user error on your part, Bruce, I'm afraid to say. There is no lens of any brand that is not sharper closing it down a bit. The reason is you're progressively excluding the 'junk' light from the very edges of the elements, the good stuff without aberrations is directly in the centre, along the axis.
Only briefly played with split prism, never owned a camera that used such a viewfinder, but I got the jist of what it's doing.

I was going to say... I've swapped out my K-1 stock screen for the Canon S Type Matte, and I feel content with that choice. It's a pro and cons thing but for me the pros outweigh the cons. It's obviously not as ideal an experience with using slower glass like the PLM or some manual focus glass stopped down. I have found it useful for using when doing Quickshift fine tuning stuff, so if the PDAF has done one of those jobs and slightly let the user down (ie gotten you to the ball park of where you need to be for correct focus, but it's slightly off), then having that Canon screen and dialling in the focus to being just right feels completely easier with less liklihood of still a poor outcome. But this is not really as possible with the PLM due to the dark/dim viewfinder experience.
So I wondered then, could the KP focus screen be swapped out for some other prism style screen where the AF system of the camera is never really expected to get you great focus but just to the ball park area and then you use the QS feature to line things up properly for the shot (without a dim screen)? I guess it would be another pro and con, BiF stuff a nightmare (who uses QS for BiF?!), but for static subjects in the middle of the frame, could be more reliable?
I dunno... just after swapping out the K-1 focus screen I'm starting to feel like Pentax's native screens are poor and having awesome options like lenses with QS is almost meaningless on those screens because you can thing you have improved and fine tuned better when in fact you made it worse


I remember either you or Beholder talking about that, 645Z would seem to be king for IQ on budget medium format cameras then...


Um, I thought some might be suggesting the Fine Adjustment for different apertures would be based around Focus Shift?


No doubt user error! But... I think I worded it incorrectly. I was meaning that it felt like PLM @300mm and f6.3 felt like focus was better thus image IQ better, when I bumped aperture to f9 or 10 and tried refocusing again.. image is soft :/ Maybe this is focus shift again with the PLM, maybe just bad luck/user error, but it feels like a regular occurrence a bit. I'm gonna test more soon.

Thanks again!

06-23-2020, 04:38 PM   #68
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QuoteOriginally posted by BruceBanner Quote
Um, I thought some might be suggesting the Fine Adjustment for different apertures would be based around Focus Shift?
Um, read again, Bruce, there is no such thing as Fine Adjustment for different apertures.

All focusing is done wide open, irrespective of what you have chosen the aperture to be.
06-23-2020, 05:22 PM   #69
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It looks like focus shift requires a different correction for every aperture <f/8. you can only correct for one so it can make sense to adjust at a specific aperture, just know you have to eyeball any other aperture if you want the eyeball in focus.
Anyone know if this shift is extreme on the 50mm a 1.7? I can never get focus at f/8? I will test it if I ever use it again. my 50mm a 1.4 doesn't have this problem so it could be aberrations.
06-23-2020, 06:51 PM   #70
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QuoteOriginally posted by clackers Quote
Um, read again, Bruce, there is no such thing as Fine Adjustment for different apertures.

All focusing is done wide open, irrespective of what you have chosen the aperture to be.
Oh sorry, I know that, I thought you meant like how that might be why people would like that as a feature in their cameras. I know some other brands allow for some in depth fine tuning for their zooms, so that you can have different values for different FL, I wondered if there is a brand that has gone so far as to do it for apertures as well O.o
06-23-2020, 08:33 PM   #71
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QuoteOriginally posted by BruceBanner Quote
Oh sorry, I know that, I thought you meant like how that might be why people would like that as a feature in their cameras. I know some other brands allow for some in depth fine tuning for their zooms, so that you can have different values for different FL, I wondered if there is a brand that has gone so far as to do it for apertures as well O.o
No. Only Pentax takes microadjustment seriously, there are entry level Canons and Nikons that don't permit the owner to do anything. Even a central adjustment is done by an authorized repairer, as I understand it.
06-23-2020, 10:46 PM   #72
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QuoteOriginally posted by clackers Quote
No. Only Pentax takes microadjustment seriously, there are entry level Canons and Nikons that don't permit the owner to do anything. Even a central adjustment is done by an authorized repairer, as I understand it.
My friend who bought a Nikon D750 I think could calibrate his Sigma Zoom, maybe it was a Sigma hub thingy? Not sure, I think he did get adjustments done for his zoom at different FL tho.

There's the Dot method as well that I saw demonstrated with a Nikon I think and it had -20 to +20, and it made it bit more sense and I think Pentax could possibly benefit from a higher scale/smaller increments. My FA77 for example needs +8 when using the dot method, but that's a bit of a guess because I can't go pass +10 to find out the other side of the mark where the lens AF confirm drops out.
06-23-2020, 11:04 PM - 1 Like   #73
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QuoteOriginally posted by BruceBanner Quote
My friend who bought a Nikon D750 I think could calibrate his Sigma Zoom, maybe it was a Sigma hub thingy? Not sure, I think he did get adjustments done for his zoom at different FL tho..
Yes, I own that hub myself. So, no, it's not Nikon.

The hub can let you do it at different focal lengths or distances (four), but not apertures.
06-23-2020, 11:16 PM   #74
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QuoteOriginally posted by clackers Quote
Yes, I own that hub myself. So, no, it's not Nikon.

The hub can let you do it at different focal lengths or distances (four), but not apertures.
I don't think any do apertures, and focus shifting from apertures is a 'old lens' issue more than exists today in modern glass, is it not?
06-24-2020, 04:26 PM - 1 Like   #75
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QuoteOriginally posted by BruceBanner Quote
I don't think any do apertures, and focus shifting from apertures is a 'old lens' issue more than exists today in modern glass, is it not?
The issue is not old versus new. It's how corrected spherical aberration is in a fast lens.

Lots of glass is the usual cure - a big, heavy, expensive lens like the DFA*50 and DFA*85 or Zeiss Otis.
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