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Forum: Pentax SLR Lens Discussion 12-24-2017, 10:14 AM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
The conversation gets a bit absurd outside of the APSc context. The Tokina/Pentax design is limited to 90 degrees horizontal FoV on crop sensor. The Sigma was designed for FF yielding an expansive 122 degree FoV - so the marginal difference in resolution from an exotic design is a given. Yet, despite the greater demands on the lens design, the Sigma is far superior in CA and lack of distortion.

The review gives the Sigma a 9.0 (excellent) rating, Pentax an 8.8 (very good) rating - playing on the latter's turf. The retail price at time of review was $829.95; that price is now roughly halved... So, the review conclusion:

If you have an unlimited lens budget, the Sigma DG 12-24 f/4.5-5.6 is the perfect choice. The lens has the least barrel distortion, vignetting, chromatic aberration, and is reasonably sharp. Why wouldn’t you buy a lens that already addresses some of the major problems of ultra-wide angle zooms?

For me, I can tolerate only so much CA, and software correction always leaves defects when the problem is so severe as in this Tokina lens design. The review sums it up correctly:

The Sigma DG 12-24 f/4.5-5.6 was the clear winner. Not only did it have very limited chromatic aberration wide open but it was consistent throughout the f-stop sample. The Tamron SP AF 10-24mm f/3.5-4.5 DI II displayed some chromatic aberration at f3.5 but improved significantly at f8 and f16. The Pentax DA 12-24mm f/4 did not do as well as the other two lenses, which was surprising. Not only did it have significant chromatic aberration at f4 but it did not improve much as the lens was stopped down.

My experience with the Tokina version of this lens (on Canon) was not so severe, but still is considerably worse than the Sigma (second sample). These UWA lenses exhibit extreme CA with only very minor decentering. This is why you get such varied test results in credible testing (especially apparent with the Sigma). It is quite certain that if you are finding greater CA on the Sigma, you have a slightly decentered copy, unfortunately.

---------- Post added 12-24-2017 at 11:34 AM ----------



Good discussion, and some nice images in that thread. Filters are helpful for the kinds of situations you posted.

Believe me, I use filters when I have the need. Way back when when I was working in a camera shop, we got great deals on fully coated filters (typically Hoya back in the days when their filters were much higher quality) because the retail mark-up was huge, and employees got them for cost+10% - $80 filters for $9, etc.

The problem with even thin filters on UWA is angle of acceptance. That's why you see the bulbous outer elements - they can manage the angle better - closer to perpendicular. Obviously, front filters are flat, causing optical degradation in the UWA field due to the severe angles involved. At least gelatin filters mounted at the rear are very thin and are less of an optical challenge. Frankly, I've never bothered with them, though, so I can't say if they are an effective solution.

A second problem is how polarizers work in sunny conditions at UWA. As is quite obvious, the effect of polarization varies considerably depending on angle to the light source (the sun). This results in increasingly uneven impact the wider the FoV. On UWA, it is almost always unnaturally distracting, and very difficult to fix in post. It can be interesting left alone as a special effect, but not my cup of tea.
Forum: Pentax SLR Lens Discussion 12-23-2017, 04:44 PM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
Yep, I get it. From my considerable experience I also get that using filters on UWA lenses create more problems than they resolve, and the Sigma is perfectly capable of taken rear gelatin filters if you feel the need. We can do considerably better using modern PP techniques. Also, the Sigma works perfectly well on film cameras (FF), even though I don't have the K-1.

As for the conclusive findings in the PF review indicating that the Sigma is the superior optic - the evidence presented - especially regarding the vastly superior CA performance for the Sigma - speaks for itself. You might have gotten a bad copy of the lens (quite common, given the exotic design), and should have sent it back if it fell short of your standards.
Forum: Pentax SLR Lens Discussion 12-22-2017, 12:21 PM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
We probably have exhausted the subject...

But I would like to mention that folks with a K-1 can look to at least one real, FF UWA option that is generally available used or as a refurbished (how I got mine) - the Sigma 12-24. Even on crop, as indicated in the direct comparison here at PentaxForums, it is a better overall optic than the Pentax/Tokina. That is - if you get a good copy (I had to return the first sample which was considerably de-centered). The pricing now falls around $400 - a bargain. Having used both optical designs, I would agree with the assessment here.

Here's that direct comparison:
DA 12-24mm vs Sigma and Tamron 10-24mm Comparison Review - The Bottom Line | PentaxForums.com Reviews

It is worth pointing out that this review was based on a crop sensor. Obviously, as the only FF lens in the comparison, the Sigma would be that much better comparing them on the K-1, but few would think to bother for obvious reasons.
Forum: Pentax SLR Lens Discussion 12-21-2017, 12:29 PM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
The problem here is that the conversation relates specifically to crop lenses on full frame sensors. Citing DXO tests of Pentax crop lenses on crop sensors isn't proving anything in a scientific sense because there is no data on more than 50% of the sensor real estate. DXO has done no testing of lenses on the K-1 body, and no extrapolation is defensible.

If we must look at myth-busting data from tests such as Photozone and Lenstip, we discover that the corner performance in comparing the FA 35 with the DA 35 is vastly different - a far cry from claims often made that these two lenses are essentially similar and should perform very close to equally well. First of all, a half-stop difference makes them indisputably different optical designs. The slower DA should have a better hedge against vignette problems, but was ranked poorer than other crop comparables by Photozone regarding light fall off. The FA is ranked best in class in vignette measurements - again comparing with other FF lenses. Beyond that, we still don't know how they will compare on actual full frame sensors - but we have a real good hint...
Forum: Pentax SLR Lens Discussion 12-21-2017, 03:46 AM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
Just trying to keep the focus on how particular lenses designed for crop perform on FF, but evidence presented by you strays elsewhere. Admittedly, the K-1 is different, a far-superior beast compared to a 5D.

I owned and heavily used that FF body for several years, and found the 12-24 design lacking for my needs. Consensus is pretty strong that as you go wider, the image quality adapting crop to FF deteriorates. Correspondingly on the long end, Pentax indicating that the 200, 300 and 560 primes are full-fledged FF capable of strong performance into the corners even wide open. Many other lenses perform quite well stopped down, including the DA 50, based on the images offered and various measurements - but only when stopped down. However, if you are forced to stop down to a greater extent, then you essentially lose the chief benefits of FF format. Comparing corner performance near wide open on my DA 50 with an old m50.f/1.4 on APSc - the old lens simply is far better with more natural transitions; the DA is very sharp in the middle, though. Then again, that old optic is better than the FF AF 50 f/1.4 from Canon, as well. These observations are based on what I find pleasing in the images, not relying on test measurements. Yeah, opinion.

Again, doubling down on me personally with comments such as "you can start your education" may provide some sort of gratification, but isn't persuasive evidence.
Forum: Pentax SLR Lens Discussion 12-20-2017, 07:45 PM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
I'm not encouraging consumerism, but rather judicious use of hard-earned dollars based on appropriate mating of body to lens. You are the one encouraging purchase of the K-1 using lenses not strongly recommended by Pentax or the guides on this site (this would be fact based information). You easily could be accused of consumerism accompanied by poor judgment.

I've cited the -.8ev light loss on APSc - which is acceptable, but not good. You should cite the information for FF - which isn't going to be good at all. You should cite some fact somewhere, if that is the basis of your meme. Not that light fall off tells the whole story, especially regarding the CA-prone 12-24 design.

Finally, "as usual" is the personal argument taken most often when one has failed to be persuasive. I'll take it as a complement, though, as I do take pride in my consistency.

Sorry, but the photos you posted in your day with the K-1 simply are not convincing - at least to my eye. Whether processed for optimal effect or not, the quality simply falls short of what I would want to present in public. We all have different ideas of what is optically pleasing, so I'm sure you would find many of my images unacceptable optically, as well. We just see things very differently on this.

---------- Post added 12-20-2017 at 09:10 PM ----------



Don't follow you at all on this point. You realize you are making a claim about a pro FF lens mounted on a crop sensor body, right? We probably do agree that FF lenses do a good job of covering a crop sensor, especially that particular lens. Not all Nikon bodies with three numbers in the model name are FF, but they are pro class...
Forum: Pentax SLR Lens Discussion 12-20-2017, 02:52 PM  
front element size - does size matter?
Posted By ScooterMaxi Jim
Replies: 68
Views: 3,723
While it comes down to a matter of how much degradation a user is willing to accept, the official stance from Pentax and echoed on the guides at this site (including the zoom and prime listings posted last month) indicate that only the DA*200, 300 and 560 qualify as full frame in the DA range. You have APSc+ designations for a few others, such as the various 40s and the 50. As for the 50, it really quite clearly suffers in the corners. Even on APSc, the light fall-off performance is somewhat marginal at -.8 ev. It is a lens that does not get at all sharp in the corners until at least f/4 - on APSc. I'm fine with the limitations of this APSc lens, given the price point.

To say it is a good-performing full-frame lens on a semi-pro body such as the K-1, though, appears to be a questionable claim at best - no matter how often repeated. Most of the K-1 users here describe it as no more than "usable."

---------- Post added 12-20-2017 at 04:25 PM ----------

I had the Tokina 12-24 on Canon crop and full frame bodies. Yeah, the Pentax is a better lens due mainly to the superior coatings, but optical design is identical. While its true that the hard vignette disappears at 17 or 18mm on FF, the quality relating to sharpness, contrast and CA is especially low outside of the APSc image circle. A cheap 17mm full frame prime lens was a vast improvement. I'm not a fan of going to FF for the sake of it, especially when the optics fitted "work" but considerably fall short of what can be achieved in a proper APSc system.
Forum: Pentax SLR Lens Discussion 12-19-2017, 07:05 PM  
What lens has the most clinical color?
Posted By ScooterMaxi Jim
Replies: 45
Views: 2,256
The lens profiles - whether LR or Capture One - are remarkably unsophisticated - focusing entirely on distortion, light fall off and CA (sometimes) - and certainly have no color correction other than basic CA adjustments.

The point I was making relates to the coded changes made at the Pentax body sensor level which is somewhat ballpark with the Adobe profiling, and more precise with Capture One. Pentax introduces significant shifts in the sensor raw processing toward magenta bias (hence "warmth") that you don't find otherwise in the Nikon handling from the same Sony-sourced sensor. (Not that Nikon doesn't over-manipulate in other ways, such as unabashed underexposure followed by heavy smoothing compensations to claim DR that in reality isn't any different than the more honest approach taken by Pentax that properly labels DR highlight expansion rather than implementing it secretly...) Bottom line, RAW is not raw at all... and getting to a "neutral" treatment involves cracking something of a trade secret.
Forum: Pentax SLR Lens Discussion 12-19-2017, 12:50 PM  
What lens has the most clinical color?
Posted By ScooterMaxi Jim
Replies: 45
Views: 2,256
You know what they say about RAW. It is raw in name only, and in-camera processing alters what's rendered from the sensor. Not that I have any scientific evidence, but the warmth in Pentax imaging varies based on particular bodies and - most certainly - the raw processing engine's profiling. It is pretty clear that Adobe (and therefore LR) profiles are put together with far less care than, say, Canon profiles (having shot both systems extensively in the days when LR was my main processor). The magenta shift problem is almost never corrected entirely when dealing with the Adobe profiles. In Capture One, Pentax and Canon profiling are pretty much equally meticulous and you get the magenta problem largely corrected.

Sorry to throw another challenging variable into the mix, but there's no doubt its another factor that makes finding "neutral" or "clinical" a nearly impossible task. You might be best off using JPEG and manual color temp - at least then you are getting what Pentax engineers intended (which, frankly, isn't neutral). You might be best off just accepting that the various lenses can be ranked from warm to cool, and you will have to accept what is closest to neutral based on your own preferences.
Forum: Pentax SLR Lens Discussion 12-18-2017, 10:51 AM  
Which of my lenses for Northern Lights?
Posted By ScooterMaxi Jim
Replies: 31
Views: 2,092
The problem is mainly related to the relative opportunity. Very bright aurora is relatively rare, and we are in the down-cycle of activity since the 2013-14 peak - bottoming out in 2020-21. So, you are likely to get only relatively moderate activity this winter. Faster and wider lenses, preferably primes, are your best bet. The Samyang 14 and 8mm for APSc are possibly good enough - but who knows? The best options are going to be expensive, of course.

The two Samyangs have minimal coma issues (assuming good copies), better than nearly any zoom. Coma is a critical concern for any astrophotography application.
Forum: Pentax SLR Lens Discussion 11-10-2017, 10:52 AM  
FA 35mm 2.0 or DA 35mm 2.8 limited
Posted By ScooterMaxi Jim
Replies: 26
Views: 1,635
Those are stunning photos. The FA 35 is very good overall, but at the close focusing on the cat, I don't think it could quite match the pop of that shot. At normal distances, the FA 35 is very good. Also agree, it tends to be just a bit warm - which might or might not be to your liking. Just as the macro has a reputation for good quality wide open, the FA is good at f/2 and excellent across the entire field by f2.2 - possibly the best lens I have at the aperture. Both lenses are capable of yielding a 3D quality. I don't think there is any question that both these lenses are considerably above average - especially for the price, but their strengths are somewhat different. As an absolute macro (1:2 or closer), I don't think 35mm is a preferable length - especially if you are planning on shooting critters. However, that isn't the main strength of that lens, IMHO, as it clearly performs extremely well as a "normal" lens.
Forum: Pentax SLR Lens Discussion 11-09-2017, 02:41 PM  
What is the most compact/light Pentax zoom lenses?
Posted By ScooterMaxi Jim
Replies: 22
Views: 1,505
I'm pretty fond of the 28-70 f/4 which is quite a bit smaller than the standard 18-55s though a bit heavier, stronger into the corners (weaker in the center), and renders nicely overall. For a constant aperture zoom, it is pretty amazing for compactness. Balances nicely on the K-01, but the build is a bit of a letdown - compared to the body.
Forum: Pentax SLR Lens Discussion 11-05-2017, 07:55 PM  
Full-frame lens on a crop body not advisable?
Posted By ScooterMaxi Jim
Replies: 168
Views: 6,655
On a more serious note, I do tend to notice some difference in general between crop lenses designed for digital and FF lenses designed for film. You tend to get a snap and saturation with the newer lenses, but a busier look in the near-OOF areas. Especially for landscapes and portraits, I tend to prefer the older, softer look that strikes me as more realistic. This became especially apparent with the DA 50 compared to the older 50s.

Not sure why that would work that way, other than differences in the coatings. One thing I really appreciate with the FF lenses is that they tend to render sharpness similarly on crop across the frame (even though they are likely to have heavier CA on the edges) whereas modern lenses often show considerable sharpness degradation toward the edges compared to the ultra-sharp center. This center-corner sharpness difference is especially apparent in comparing the FA 35 to the DA 35 on crop.
Forum: Pentax SLR Lens Discussion 11-05-2017, 02:33 PM  
Full-frame lens on a crop body not advisable?
Posted By ScooterMaxi Jim
Replies: 168
Views: 6,655
Interesting... I have the Tamron 28-75 lens in Canon mount where it was used both for crop and FF needs. Photozone indicates that the lens performs especially well on crop, but the edges and corners have too many issues for FF. I found that it was really fine at FF when stopped down to f/4, but not adequate wide open (no lens I've owned has dramatically improved so much in a single stop). I'm just the opposite in terms of my shooting needs. I really enjoy lenses that go from wide to mild telephoto - with "normal" roughly in the middle. Starting at normal feels very limiting to me.
Forum: Pentax SLR Lens Discussion 11-05-2017, 01:27 PM  
Full-frame lens on a crop body not advisable?
Posted By ScooterMaxi Jim
Replies: 168
Views: 6,655
Nothing finer than an English cocker for a good excuse; wonderful dogs. It was pretty clear you knew the right stuff, but didn't want others confused.
Forum: Pentax SLR Lens Discussion 11-05-2017, 10:55 AM  
Full-frame lens on a crop body not advisable?
Posted By ScooterMaxi Jim
Replies: 168
Views: 6,655
I'm sure you meant that standing further away "increases" DoF - that is, it becomes less shallow with distance. Otherwise, the point is valid.

What folks tend to forget is that the smaller the sensor the greater the magnification needed. That's where you sense the loss of resolution. Of course, the image circle of a lens has nothing to do with that.
Forum: Pentax SLR Lens Discussion 11-04-2017, 07:23 PM  
The Pentax DA* 11-18mm F2.8
Posted By ScooterMaxi Jim
Replies: 82
Views: 6,374
It's a pre-production model that still has the Tokina markings for a lens introduced more than five years ago. That should help with the LBA concerns.
Forum: Pentax SLR Lens Discussion 10-31-2017, 10:06 AM  
How 'Bad' is DAL 18-55 vs Other Options?
Posted By ScooterMaxi Jim
Replies: 67
Views: 3,344
The right answer comes down to personal needs and what you are willing to spend. The Pentax 18-55 WR is the best value if you need the weather resistance, and are willing to stop down to f/7.1 or more (assuming a good copy). If you need speed (extra light gathering in dim conditions), the Tamron is excellent by f/4, but has a reputation as having less than solid build. I'd be least enthusiastic about the Sigma, but if the slightly extra reach is important to you - worth considering.
Forum: Pentax SLR Lens Discussion 10-05-2017, 08:09 AM  
Opinion needed: DA 40mm f/2.8 - Yes? No?
Posted By ScooterMaxi Jim
Replies: 28
Views: 2,463
Lea, I know a lot of folks swear by that Sigma 30, and are especially fond of it for its sharpness in the center especially. I've seen a lot of fine images taken with it, and much like my Sigma 17-50, it just doesn't impress as much as tests indicate due to the neutral-to-cool coloration and sense of depth somewhat lacking. I like the warmth found on most of the Pentax lenses, even if they might not have the highest sharpness. Also, keep in mind that the Sigma is a somewhat wide angle lens designed only for crop sensors. I would be very surprised if the corner sharpness and light fall off holds up well on full frame.

Others with direct experience might have a different viewpoint.
Forum: Pentax SLR Lens Discussion 10-03-2017, 10:30 PM  
Opinion needed: DA 40mm f/2.8 - Yes? No?
Posted By ScooterMaxi Jim
Replies: 28
Views: 2,463
Well you got in under the two-year limit for responding. The decision was long in coming, but is the right one.

I love my DA 40xs, but see absolutely no reason to try to extend its capability to FF. The body is huge, the little lens is capable on crop, but much like the m40 upon which it is based, not a good choice for FF. You love the FF FA 50, and you would be unsatisfied with the only slightly wider 40mm. The better choices are at 35mm, and the FA35 especially gives you a far better prime step. You will notice a different character to the FA 35, more film like with better bokeh (much like the 40s, but far sharper into the corners). Not as sharp or contrasty in the center compared to any of the 50s, but more natural overall. It might be tempting to go with the DA 35 to save a few dollars, but the FA 35 will be far superior into the corners. Despite the myth forwarded here, the DA vs. FA 35 are not at all similar, especially into the corners (even on crop, let alone FF).
Forum: Pentax SLR Lens Discussion 10-02-2017, 11:15 AM  
Unusual inscription on Pentax-M 50mm f/1.4
Posted By ScooterMaxi Jim
Replies: 10
Views: 793
Back in my camera shop gear selling days around 1980, Pentax (and the other major brands) often provided deeply discounted bodies and lenses sold directly to the retail representatives - for obvious reasons.

Of course, Pentax didn't want to see a black market emerge from these sales, so the inscriptions were the logical move. I went with an LX and m50 f/1.4. I'm sure the SAMPLE inscriptions were also intended to ensure that the sales representatives didn't cycle through stock (mostly a matter discouraging unopened boxes becoming samples). Those reps were displaying and packing up at least once a day.

My biggest issue came with the LX (a body that never got me feeling wowed despite the many pro options available) which had the deeply set inscription right below the shutter cock lever, and due to the softer metal caused some indentation surrounding the heavy scribe. Seeing that I was surprised that it didn't impede the shutter advance. Sure enough, within about four months, the shutter advance mechanism failed - repaired under warranty.

The lens inscription looks much nicer than how the body came out:
http://www.jamesrobins.com/Photo-tests-/M50mm/n-J9JMHR/i-xFMD7rC/A
Forum: Pentax SLR Lens Discussion 09-19-2017, 07:13 PM  
Samyang 85mm f/1.4 or SMC Pentax M 85mm f/2?
Posted By ScooterMaxi Jim
Replies: 75
Views: 6,092
Wow, I thought mine took the cake when it comes to turning a blind eye. Pretty sure I couldn't get away with flashing a 645z without a pointed question. And, if the question was, "What did that cost?" doubt that saying "less than half what the Hassy version costs" would get me out of that pickle.
Forum: Pentax SLR Lens Discussion 09-02-2017, 08:04 PM  
Looking for versatile everyday lens...
Posted By ScooterMaxi Jim
Replies: 40
Views: 2,206
I'd have to wonder if you got a slightly off Sigma 17-50 because there shouldn't be much difference in sharpness between the two when stopped down. Possibly contrast, rendition and saturation favor the Pentax 16-85, but it would be good to know how you get to "greatly outperforms." Personally, for serious landscape work, especially in marginal light, I would rely only on primes. Especially so toward the wide angle side of things, you simply get more consistently sharp results with lower CA issues - and wide zooms tend to have so much field curvature (the major failing of the Tamron 17-50, for instance).
Forum: Pentax SLR Lens Discussion 09-01-2017, 05:11 PM  
Looking for versatile everyday lens...
Posted By ScooterMaxi Jim
Replies: 40
Views: 2,206
Well, we are really speculating based on our own priorities at this point. It isn't clear what the OP wants in terms of IQ, size, lens speed, build and pricing. We're just sharing our particular needs. Norm is absolutely right, assuming that the OP is willing to compromise a bit on IQ, wants low pricing, and seeks considerable reach. Bottom line, there are a lot of good choices out there for mid-range zooms - even in Pentax.

It is entirely possible that we have provided a bit more feedback than the OP is wanting to process. Might be best to say look at the lens reviews on this site, but narrow choices based on needs before you look at all those options.

I want the one that is really small, super fast, plenty of reach, excellent build and extremely high IQ at a very low price. Can hardly wait until that one shows up.
Forum: Pentax SLR Lens Discussion 08-31-2017, 08:32 AM  
Looking for versatile everyday lens...
Posted By ScooterMaxi Jim
Replies: 40
Views: 2,206
Although I don't own one, I agree overall with the sentiment regarding the 16-85 given the high quality of the images it produces. It doesn't work well for me due to the size and relatively slow aperture. I have the Sigma 17-50 (even a bit larger) and find it performs well in pretty much every situation - especially so toward wide open. Brooke is right about the Tamron 28-75 (having shot it extensively on Canon both FF and crop), but it isn't a single lens solution on a crop camera; it also isn't as strong wide open as the Sigma (but is excellent already by f/4).
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