Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-24-2017, 01:21 AM   #31
Kiwi Pentaxian
Loyal Site Supporter
NZ_Ross's Avatar

Join Date: Mar 2012
Location: Timaru
Photos: Gallery | Albums
Posts: 3,679
QuoteOriginally posted by grispie Quote
Personally i'd wish them to come out with a wide prime first, but it seems logic to me, to gain professionals, the classic 50 & 85 need to be there first..
No?
I think we will see the 35/50/85 primes before we see a WA/UWA in the 18-25mm range.

I think there is plenty of demand for a DFA* 20 or 24 which is fast and weather sealed, but 35/50/85 is a classic prime set and well accepted in the market.

02-24-2017, 01:37 AM   #32
Senior Member




Join Date: May 2014
Posts: 292
Original Poster
QuoteOriginally posted by grispie Quote
Personally i'd wish them to come out with a wide prime first, but it seems logic to me, to gain professionals, the classic 50 & 85 need to be there first..
No?
For professionals then I think a 20mm prime should have been a high priority rather than the 50mm. You have to consider that the k1 users are in a high number landscape users. But hey, that's my opinion. I could be wrong. It could well be that they are already making a wide prime and it is gonna be that good that it just needs a bit more time to perfect.... like the k1 did
02-24-2017, 03:59 AM   #33
Pentaxian
aurele's Avatar

Join Date: Jan 2011
Location: Paris, France
Photos: Albums
Posts: 3,208
QuoteOriginally posted by bobbotron Quote
An f4 20(ish) WR pancake that's razor sharp at f8 would be a killer lens for the system.
almost every lens is sharp at f8 ....
02-24-2017, 05:12 AM   #34
Loyal Site Supporter
Loyal Site Supporter
monochrome's Avatar

Join Date: Mar 2008
Location: Working From Home
Photos: Gallery | Albums
Posts: 26,241
If their vision over the coming 5 and 10 years is to establish a professional presence in Wedding and Studio it stands to reason they need superb, in-house 35/50/85. In the interim they still have 31/43/77.

They covered Trinity zooms effectively, while simultaneously demonstrating their chops.

I thought 2018 was Year of the Prime. I expected (from posted suggestions and sourced rumors) 5-6 primes this year. Unless they drop f/2.8-ish D FA primes out of the sky, where are they?

02-24-2017, 06:43 AM - 1 Like   #35
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 36,707
QuoteQuote:
I like my DA15, but it can't match my Samyang 14mm. And it's why there's a DA14.
If memory serves me well, the DA 14 does't match the DA 15

If that's your argument, you don't have an argument.

DA 14


DA 15


The DA 15 is always better in the centre, and for landscape, ƒ5.6 to ƒ11, it's better centre and edge, being excellent at the edge at ƒ8,. The DA 14 is never excellent at the edge, anywhere in it's range.

I could go on, my DA 18-135 kicks the DA* 16-50s butt from anywhere but about 18mm if memory serves me well.
FA 50 macro definitely holds up compared to the DA* 55 1.4 or FA 50 1.4 so one has to ask, where are the examples that prove this point?

With Pentax lenses to date , my guess is the exact opposite is true, these are three random lenses. In three tries i didn't find one example to support your notion.

It might be possible that theoretically it's true, but in that case clearly, manufacturers have trouble producing the lens tolerances that would make it true practically.

But thinking of the compound lens diagrams I had to analyze 50 years ago when I took optical physics in a lens design course, I am really suspiscious. Practically, the sharpest part of the lens is the smallest aperture, until diffraction sets in. Most lenses on APS-c and FF are sharpest at ƒ5.6 although the very best may be sharpest at ƒ2.8 or ƒ4. An ƒ4 lens should be fine for producing an ƒ5.6 image.

Only the 31 and DA 70 qualify in the "really good lens that is sharper at ƒ4 than ƒ5.6 " category among Pentax lenses, maybe other manufacturers have more and there are examples from other manufacturers, that don't really apply to Pentax glass.

Last edited by normhead; 02-24-2017 at 07:21 AM.
02-24-2017, 07:15 AM   #36
Loyal Site Supporter
Loyal Site Supporter




Join Date: Jul 2013
Location: Cumming, GA
Posts: 792
QuoteOriginally posted by dcshooter Quote
spherical distortion can can be very desirable
That is specialized and there is a lens type dedicated for it and that is Fisheye.
02-24-2017, 07:29 AM   #37
Site Supporter
Site Supporter
bobbotron's Avatar

Join Date: Jan 2015
Location: Ottawa, ON
Photos: Gallery
Posts: 2,793
QuoteOriginally posted by clackers Quote
Bigger is better for IQ, Bobbotron.

I like my DA15, but it can't match my Samyang 14mm. And it's why there's a DA14.

UWAs are much harder to get right than teles.

Roger Cicala wrote a very good column about this. I can find it if you like.
Sure, I'd be interested to see that article if you can find it.

I guess I'm not totally convinced yet.
02-24-2017, 07:34 AM   #38
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 36,707
QuoteQuote:
I guess I'm not totally convinced yet.
My level of convinced is probably a little less than that.

But then I'm basing my opinion on actual evidence.

One would have to explain why if you took a 1.4 lens and ground off a half cm making it an F2 lens, the remaining f2 glass would be less sharp, or have less distortion than it had before. That's not going to happen.


Last edited by normhead; 02-24-2017 at 07:40 AM.
02-24-2017, 07:43 AM   #39
Site Supporter
Site Supporter
bobbotron's Avatar

Join Date: Jan 2015
Location: Ottawa, ON
Photos: Gallery
Posts: 2,793
QuoteOriginally posted by normhead Quote
My level of convinced is probably a little less than that.

But then I'm basing my opinion on actual evidence.

One would have to explain why if you took a 1.4 lens and ground off a half cm making it an F2 lens, the remaining f2 glass would be less sharp than it was before. That's not going to happen.
I'm trying to practice being polite on the intertubes in 2017. Agree to disagree and whatnot. clackers could definitely be right, however I would argue one could be serious about landscapes, but also be willing to take a slight IQ hit and not hike around a big piece of glass. Priorities.

Ugh, I attempted to get evidence to further discussion here, but I find looking at and comparing MTF graphs to be a rather joyless exercise.
02-24-2017, 08:07 AM - 1 Like   #40
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 36,707
QuoteOriginally posted by bobbotron Quote
I'm trying to practice being polite on the intertubes in 2017. Agree to disagree and whatnot. clackers could definitely be right, however I would argue one could be serious about landscapes, but also be willing to take a slight IQ hit and not hike around a big piece of glass. Priorities.

Ugh, I attempted to get evidence to further discussion here, but I find looking at and comparing MTF graphs to be a rather joyless exercise.
Really, I only post lenses I've compared in the past. I used to obsess on this kind of thing a fair bit. There could be a host of other lenses out there for systems other than Pentax that prove clacker's right, but as a general rule, for Pentax gear, it's not worth paying attention too.

The first thing any first year lens student like myself will tell you is, it's much harder to make a wide aperture lens than a narrow one. Just the size of the elements makes many design options impossible. But that being said, theoretcally it could be true. I once got into a similar discussion with Falconeye about lenses peaking at ƒ5.6. It turns out that the best lenses will have their highest resolution at ƒ2.8 or ƒ4, and he explained mathematically why. The problem for the average shooter was that those lenses are so expensive, the average shooter doesn't contemplate buying them, it takes incredible accuracy in manufacturing tolerances to get it right.

SO even though it's a mathematically proven principle, it's irrelevant to the average shooter. I'm wondering if this is a similar principle.

That is what happens when you use the math to guide you. What theoretically could be is often not what is out there practically.
02-24-2017, 10:40 AM   #41
Veteran Member




Join Date: Mar 2013
Location: Hamilton, Texas
Photos: Gallery | Albums
Posts: 706
QuoteOriginally posted by Mattox Quote
So, is it just me or is anyone else gutted by the news of only a 50mm and 85mm prime at the opening day of the CP+? Is was really really hoping to see atleast a few mockups of some more interesting wide angle primes such as a 20mm. The k1 (being the best landscape camera in its class) is crying for such a lens in my opinion
I wouldn't say "gutted", but I will say there's nothing of interest to me. What's with these giant lenses? (And where's the Q-mount telephoto macro lens that we've been promised for years already?)

I was much more intrigued by the Voigtländer E-mount primes. Manual focus. Manual aperture ring, with ten iris blades. Body design could be mistaken for a Super-Takumar. Electronics included for data communication with the camera body. Nocton 40mm F1.2, claimed to be the fastest 40 ever for full-frame, and yet it's no giant. My decision to go with the Sony seems better all the time.
02-24-2017, 11:02 AM   #42
Pentaxian
normhead's Avatar

Join Date: Jun 2007
Location: Near Algonquin Park
Photos: Gallery | Albums
Posts: 36,707
QuoteOriginally posted by Tony Belding Quote
I wouldn't say "gutted", but I will say there's nothing of interest to me. What's with these giant lenses? (And where's the Q-mount telephoto macro lens that we've been promised for years already?)

I was much more intrigued by the Voigtländer E-mount primes. Manual focus. Manual aperture ring, with ten iris blades. Body design could be mistaken for a Super-Takumar. Electronics included for data communication with the camera body. Nocton 40mm F1.2, claimed to be the fastest 40 ever for full-frame, and yet it's no giant. My decision to go with the Sony seems better all the time.
I'm unclear on why you like these things....
QuoteQuote:
Voigtländer E-mount primes. Manual focus. Manual aperture ring, with ten iris blades. Body design could be mistaken for a Super-Takumar.
Super Taks are so 30 years ago.
Let's just leave it as, your opinion may not be widely shared.
02-24-2017, 11:45 AM   #43
Veteran Member




Join Date: Mar 2013
Location: Hamilton, Texas
Photos: Gallery | Albums
Posts: 706
QuoteOriginally posted by normhead Quote
I'm unclear on why you like these things....
Several reasons: Since I've decided autofocus can't be trusted anyhow, the best manual focus experience comes with a lens designed for that. Ten aperture blades makes for smoother bokeh when the iris isn't wide open. The relatively small size conforms with the size of the camera body, and it lets me keep the form factor similar to what I had in 35mm film SLR days. And as for the build quality, fit-and-finish. . . Well, it's nice. Super-Takumars are lovely, and if Voigtländer want to mimic that, they sure could have done worse.

QuoteQuote:
Super Taks are so 30 years ago.
I still use them.

QuoteQuote:
Let's just leave it as, your opinion may not be widely shared.
That's OK, I'm used to it.
02-24-2017, 01:34 PM - 1 Like   #44
Pentaxian




Join Date: Feb 2010
Location: Northern Michigan
Photos: Gallery | Albums
Posts: 4,499
QuoteOriginally posted by clackers Quote
It reduces distortion and vignetting, both of which lead to less resolution at the edges and corners of your pic.
There's no necessary connection between distortion and vignetting. Some of the high-end m43 lenses suffer from quite a bit of distortion and vignetting, yet are quite sharper edge to edge (sharper edge to edge than most Pentax DA lenses). The biggest disadvantage with smaller lenses is you have to use more expensive glass to high end performance. There's a reason why the Samyang lenses are so large: it's cheaper to make them that way. High-end m43 glass is chock full of exotic (and presumably expensive) lens elements.

QuoteOriginally posted by clackers Quote
Bigger is better for IQ, Bobbotron.
Bigger is only better when all else is held equal. But all else is rarely held equal. As a landscape photographer, I want high quality, slow aperture glass. Part of the reason the DA 15 is so small is that it's an f4 lens. Smaller aperture helps make the lens smaller, reduces the amount of glass needed in the lens, and, in high end optics, improves flare control and contrast. Edge to edge sharpness is nice, but lens contrast, color rendition, and flare control (all of which tend to be related) are more important to me. I can put up with a bit of reduced resolution at the edges and corners, but I won't put up with reduced contrast or less than pleasing color rendering. I own the Rokinon 10/2.8 lenses. It's a nice lens. It's easier to get sharp edges with that lens than with my DA 15. But the images from the DA 15 consistently look better than from the Samyang derived lens. The DA 15 renders detail in a more natural way, features superior color and contrast, and of course is more resistant to flare.

The DFA* 50 and DFA* 85 both look like great additions to Pentax's FF lineup, but neither of them are ideal as landscape lenses. And it's not just the size that's the issue. The f1.4 (which contributes mightily to the size) is just not needed in landscape photography.
02-24-2017, 01:44 PM   #45
Kiwi Pentaxian
Loyal Site Supporter
NZ_Ross's Avatar

Join Date: Mar 2012
Location: Timaru
Photos: Gallery | Albums
Posts: 3,679
QuoteOriginally posted by normhead Quote
The DA 15 is always better in the centre, and for landscape, ƒ5.6 to ƒ11, it's better centre and edge, being excellent at the edge at ƒ8,. The DA 14 is never excellent at the edge, anywhere in it's range.
Norm, thank you for that information. A couple of years ago I had 3 lenses around this focal length - the DA14, DA15 and one other I can't remember which. I decided it was a bit excessive having that many, and wanted to free up some cash to purchase a different lens. So I went out and tested them in a landscape, and in the end I landed with the DA15, which I still have. I did that just by comparing the images I had made, and what looked best across the range with landscapes.

I probably should have looked at charts as well - but I wanted real world with my own gear and images.

I am still happy I kept the DA15

If Pentax does produce a new reference level DFA* lens in the 18mm to 25mm range I will purchase it.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
circle, corner, cp, distortion, frame, image, k-mount, lens, lens line, pentax, pentax lens, primes, sharpness, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ricoh Imaging at CP+ 2017 Kunzite Pentax News and Rumors 209 02-24-2017 11:45 AM
645 and CP+ 2017 unkipunki Pentax Medium Format 31 02-23-2017 09:45 PM
CP+ 2017 Pentax Interview Questions Adam Pentax News and Rumors 214 02-23-2017 12:10 AM
Changes in Sigma lens line up Hornet Pentax SLR Lens Discussion 13 01-23-2016 02:16 AM
Your planned FF lens line up bpv_UW Pentax SLR Lens Discussion 55 01-08-2016 02:56 AM



All times are GMT -7. The time now is 02:48 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top