[FozzFoster]

The DFA is WR

uhhh.. yeah I know. I'm saying the weather outside sucks. not that the lens sucks.

[Andrea K]

At f/2.8, that's to be expected - and it's still not bad by any means. It's not huge CA... I own a few lenses that justify that description, but not the D FA100/2.8 WR. Remember, this is a macro lens, first and foremost. You can use it for other things, sure... but in its macro role it's usually going to be stopped down to at least f/8 - more likely f/16 or even smaller. The results at f/5.6 were rather good in my view... That's really very minimal CA. I had to look carefully to actually see any in your examples

The incamera MTF and the tests that you can find online put his best at 5,6, also for borders.

I see that you see the CA in my examples

[BigMackCam]

The incamera MTF and the tests that you can find online put his best at 5,6, also for borders.

Indeed, though that's not where it performs best for CA.

I see that you see the CA in my examples

I do. Just not very much of it

[UncleVanya]

Indeed, though that's not where it performs best for CA.



I do. Just not very much of it

Looking at opticallimits website I'm hard pressed to find any macro that performs better - admittedly they test at non macro ranges.

I find your ca results instructive and to be honest I didn't really notice the ca until I zoomed up the image and looked for it. I frankly find those results very reasonable. But each of us has different tolerance for this I suppose. Fotlr my peace of mind what macro do you feel out performs the DFA 100 WR in the CA dept?

[stevebrot]

I'm not a big fan of the D-FA macros, I think that a macro lens has to have ED / APO elements inside to avoid CA:

That is an interesting comment. I only own two macro lenses, neither of which have ED/APO elements and neither of which exhibit CA (LoCA or LaCA). No purple fringing either.*

Given that those are 100% crops, the CA seems anything but huge to me. It's rather minimal, IMHO.

As in not visible on my monitors either...

FWIW, a change seen due to "correction" in PP is not evidence of CA in the original image.


Steve

* PF is related to LoCA, but not the same thing. Lenses with LoCA may show fringing, but only on digital sensors.

[UncleVanya]

That is an interesting comment. I only own two macro lenses, neither of which have ED/APO elements and neither of which exhibit CA (LoCA or LaCA).



As in not visible on my monitors either...

FWIW, a change seen due to "correction" in PP is not evidence of CA in the original image.


Steve

I see slight purple hue in the ones with ca. But it is mild and subtle compared to the screaming purple some lenses deliver.

[BrianR]

I find your ca results instructive and to be honest I didn't really notice the ca until I zoomed up the image and looked for it. I frankly find those results very reasonable. But each of us has different tolerance for this I suppose. Fotlr my peace of mind what macro do you feel out performs the DFA 100 WR in the CA dept?

The DFA50 seems to outperform the DFA100 in the CA department (and a bit in the sharpness department). At least, in a year with the dfa50mm I've yet to see any CA I strenuously objected too, but I also haven't made any attempts to seek out and find it in the situations where the dfa100 gives me pains.

No one has commented on my CA example, it's the last post of page 3 so these sometimes get lost. Please go look, and tell me if this sort of CA on the DFA100mm is reasonable, keep in mind it is the entire image and not a crop.

[BigMackCam]

No one has commented on my CA example, it's the last post of page 3 so these sometimes get lost. Please go look, and tell me if this sort of CA on the DFA100mm is reasonable, keep in mind it is the entire image and not a crop.

Hi Brian - my apologies, I had viewed your example but didn't yet get around to commenting.

Honestly, I'm not surprised with your result, and I don't find it unusual or excessive in this use case. I wouldn't normally shoot my own WR copy of the lens at f/2.8 where extremely high contrast edges - especially bright highlights - are present, for precisely this reason. I've used it happily enough for a few portraiture shots, but even here I'd be very careful if strong back-lighting was involved.

Whilst this lens can be used for many different purposes, it's optimised for macro work. Amongst its peers, it seems to perform quite well, and to expectations.

[stevebrot]

I see slight purple hue in the ones with ca. But it is mild and subtle compared to the screaming purple some lenses deliver.

What I am seeing is a small band in the coating reflection on left image of the first example that might be taken as lateral CA that was correct in the PP'ed example. Whether this is due to aberration or the nature of the coatings is hard to say, though I know from experience that CA correction in PP is based on pattern recognition and will "correct" legitimate detail such as prismatic color in the subject.

What is perhaps more interesting is that the two example images may look quite different depending on monitor. For example, neither example shows anything looking like typical PF on the calibrated monitor for my main workstation. Both show slight bluish fringing (to the right side of one of the coating reflections) on my laptop's display, but not enough to trigger my alarms. Of course, one's tolerance to this sort of thing varies.

It may be noted that the Pentax Forums detailed review of the D FA 100/2.8 WR did note PF, though only in the corners or with extreme overexposure, the latter being an indication of the digital component of PF. Almost any lens can be incited to bad behavior with sufficient provocation.

It is easy to state that no macro lens lacking ED glass or APO design is adequate, but doing so ignores that macro lenses are typically much better corrected than other types at similar focal length, despite generally lacking the APO designation.* Field examples of CA with close-up or macro subjects are somewhat hard to demonstrate. (Yes, I just finished a quick survey of several hundred examples of my own images where CA or PF should have been present if the lens were prone. For my case, that would be with the Tamron SP 90/2.8 72B or Sigma 50/2.8 EX DG Macro.)


Steve

* One example does come to mind, specifically the Cosina/Voigtlander 125/2.5 APO Lanthar Macro, an increasingly rare and expensive lens of sterling reputation.

[BrianR]

Hi Brian - my apologies, I had viewed your example but didn't yet get around to commenting.

No worries! I just thought my example (and I have several more like it, some even worse) flew in the face of the sentiment that "the CA is not that bad".

Honestly, I'm not surprised with your result, and I don't find it unusual or excessive in this use case. I wouldn't normally shoot my own WR copy of the lens at f/2.8 where extremely high contrast edges - especially bright highlights - are present, for precisely this reason. I've used it happily enough for a few portraiture shots, but even here I'd be very careful if strong back-lighting was involved.

So, that's the thing. I do tend to avoid these situations, but at the same time it's somewhat annoying having to alter my preferred compositions or lighting arrangements due to a lens deficiency. I understand it's a compromise for having such a tiny package, and I absolutely adore both my dfa macros as they are.

As you say, it performs up to expectations, but it is also important to be realistic with those expectations and to take into account how often (if ever!) you'd be using it in less optimal situations that highlight its weakness.

[stevebrot]

No one has commented on my CA example, it's the last post of page 3 so these sometimes get lost. Please go look, and tell me if this sort of CA on the DFA100mm is reasonable, keep in mind it is the entire image and not a crop.

Sorry for not commenting! That is some pretty impressive CA, I must say...not subtle at all.


Steve

[BigMackCam]

No worries! I just thought my example (and I have several more like it, some even worse) flew in the face of the sentiment that "the CA is not that bad".

So, that's the thing. I do tend to avoid these situations, but at the same time it's somewhat annoying having to alter my preferred compositions or lighting arrangements due to a lens deficiency. I understand it's a compromise for having such a tiny package, and I absolutely adore both my dfa macros as they are.

As you say, it performs up to expectations, but it is also important to be realistic with those expectations and to take into account how often (if ever!) you'd be using it in less optimal situations that highlight its weakness.

I agree, it's important to take the limitations of a lens into account, and setting expectations accordingly.

I'm always wary when shooting *any* lens wide open. Or, rather, when I choose to shoot them wide open (and I frequently do, for creative use of DoF), I immediately accept that many aspects of that lens will be performing well below ideal levels. For example, my FA50mm f/1.4 wide open has less contrast, the resolution isn't stellar, the in-focus to out-of-focus transitions can look quite ugly. It can still be used very effectively at f/1.4, but those limitations have to be understood and accepted if the lens is to be used in this manner. All of the lenses I own have their own limitations when used at or close to maximum aperture.

Given the above, I wouldn't expect the best from the D FA100 f/2.8 (WR) wide open. It's usable, sure... In fact, I think it does remarkably well - but with some limitations, as we've seen.

I think you hit the nail on the head re compromise. Recently, we've seen some very big, complicated and expensive lenses coming to market - in Pentax land, the D*FA50/1.4 would be a good example - that really push the boundaries of performance at maximum aperture.

My point in all this was regarding @Andrea K; and the "huge CA" comment. With my sincere respect to Andrea, I see CA, but I don't consider it huge within this class of lens, especially when used with the same precautions I'd apply to anything other than the latest, biggest, most complicated and expensive glass...

EDIT: I also own the Tamron 90mm f/2.8 Di Macro, but in Sony A-mount. My personal experience suggests that, stopped down, the Tamron has the edge in CA performance in "extreme" situations. I also slightly prefer the out-of-focus rendering with the Tamron, though it's a close-run thing. And if out-of-focus highlights are in the image, the advantage swings back to the Pentax because of the rounded diaphragm. I consider both lenses to be excellent, though I have a small preference for the Tamron, but there's really not much in it

[BrianR]

And if out-of-focus highlights are in the image, the advantage swings back to the Pentax because of the rounded diaphragm.

Have you ever done side by side comparisons? I've asked a few people regarding the DFA100mm WR and the non-WR model and few seems to care. You 'get' that it's the out-of-focus highlights and not the general mashed out of focus areas where the aperture shape matters the most, so I figured I'd ask. Actually, this could be a job for Ash whose time I have already imposed upon. The FA100 looks to have the same 8-blade aperture design as the non-wr dfa100mm, but a comparison with the 9-bladed tamron would also be interesting.

I ask because one of my initial photography loves was frogs in ponds, so plenty of out-of-focus highlights and also often plenty of light/dark edges. So I'm often confronted with the choice of stopping down to reduce the CA but then losing out on the slightly annoying octagonal highlights.

[BigMackCam]

Have you ever done side by side comparisons? I've asked a few people regarding the DFA100mm WR and the non-WR model and few seems to care. You 'get' that it's the out-of-focus highlights and not the general mashed out of focus areas where the aperture shape matters the most, so I figured I'd ask.

I'm afraid I haven't done side-by-side comparisons, Brian My views are based only on independent personal use of the D FA100/2.8 Macro WR on my APS-C Pentax gear, and the Tamron 90/2.8 Di Macro on Sony full-frame. Clearly there are numerous variables. But my general impression is that I very slightly prefer the Tamron, though not enough to be in any way dissatisfied with the Pentax lens. Quite the contrary. Wide open, both lenses produce round out-of-focus highlights. Stopped down, the Pentax lens wins by continuing that shape. But the general out-of-focus rendering of the Tamron is, to me, ever-so-slightly more attractive. That's not to say it's better - just that I think I like it better. I also think it's highly subjective and, in the scheme of things, quite insignificant.

I'm not opposed to performing some side-by-side tests in future, but couldn't commit to a time-frame just now. Proper comparisons - those with any real value - would require a suitable, varied target and consistent lighting to give a fair appraisal of each lens. I could take some hand-held test shots with each easily enough, but I'm not sure I could reliably demonstrate what I've discussed...

[Andrea K]

My point in all this was regarding @Andrea K; and the "huge CA" comment. With my sincere respect to Andrea, I see CA, but I don't consider it huge within this class of lens, especially when used with the same precautions I'd apply to anything other than the latest, biggest, most complicated and expensive glass...

Yep, you are right. "Huge" is the wrong word, I already edited my original post. But the problem is real and often you can't take precautions to avoid it. The CA eats details and in MACRO photography this is bad

A "target" macro? The PENTAX 200mm serie or the APO Lanthar 125mm ... but they have other dimensions, weight and cost...