Some corner softness is no big deal. My eyeballs have it; not returning them.

**Michail_P** · 01-09-2021, 02:02 PM

Originally posted by robgski

I agree, the life of a pixel-peeper must be dreary and disappointing.

my DA 18-135mm WR is a keeper

Disappointing, frustrating and never to be satisfied, I guess. I'll never let myself go there.

tibbitts · 01-09-2021, 02:43 PM

In the digital era we can simulate inadequate edge/corner performance pretty easily. We can't simulate adequate edge/corner performance. Images can be "sharpened" but that doesn't create detail that wasn't there to start with. I'm not really that hard-core about sharpness - my cameras are 16mp with aa filters, and sometimes I use (horrors!) f16 (or smaller!), which should be severely diffraction-limited on crop sensors. Still many of the lenses I have or have had are are just obviously not sharp across the frame, even stopped down to f8 or f11 etc. Some of were okay in the 6mp era but not now.

**goatsNdonkey** · 01-09-2021, 02:46 PM - **1 Like**

Originally posted by photoptimist

@goatsNdonkey covered most of the key dimensions of the debate. Yes, some shots for some types of photographic genres (astro, art/archival reproduction, architecture, and landscape) do benefit from corner-to-corner sharpness. And most other photos work beter with central sharpness and edge/corner softness (either due to the lens or bokeh/out-of-focus conditions).

One big factor that can favor of soft-corner-lenses in almost all genres of photography is that sharp-corner lenses tend to be large, expensive, and have limited or no zoom. For on-the-go photography on a budget or with weight constraints, a lens such as the 18-135 WR is far far superior to a bag full of sharper lenses. In the realm of travel and hiking photography, the photographer with a single light-weight zoom will get more shots of more different subjects than the photographer who was burdened by carrying and swapping a bunch of heavy, sharp lenses.

Sometimes it's better to have a soft-corner image than no image at all because the sharp-corner-lenses were too expensive, too heavy to carry on a trip/hike, or took too long to swap.

Also, there are so many lenses that get better corner sharpness closed down a couple of stops, and, if a zoom, zoomed in or out from its extremes where the most design compromises have been made--consequently a lens that can give soft corners, might be employed in ways that give acceptable corner sharpness for many if not all images. It does help to really know how to use a particular lens and how to get it to rise above its limitations.

**goatsNdonkey** · 01-09-2021, 02:53 PM

Originally posted by tibbitts

In the digital era we can simulate inadequate edge/corner performance pretty easily. We can't simulate adequate edge/corner performance. Images can be "sharpened" but that doesn't create detail that wasn't there to start with. I'm not really that hard-core about sharpness - my cameras are 16mp with aa filters, and sometimes I use (horrors!) f16 (or smaller!), which should be severely diffraction-limited on crop sensors. Still many of the lenses I have or have had are are just obviously not sharp across the frame, even stopped down to f8 or f11 etc. Some of were okay in the 6mp era but not now.

tibbits, could you say more about the kinds of lenses you employ to achieve really good corner, edge, and across the frame sharpness of the kinds you need. It sounds very interesting to me, and, also, it seems ***practical*** for a person know where they really need to go, in order to fulfill those kinds of requirements, rather than picking on consumer-level lenses which, even if good to very good, weren't made to go all the way there.

**goatsNdonkey** · 01-09-2021, 03:20 PM

Art Sinsabaugh got pretty good edge and corner sharpness in the contact prints he took from negatives made with his 12x20 inch banquent camera. I saw framed contact prints up close when he came to visit one of my classes at Monmouth College in the early 1970s.

Here's an article about him:
ART SINSABAUGH: “Life on the Road: Art Sinsabaugh’s Midwest Landscapes” (2005) – AMERICAN SUBURB X

[ CORRECTION for the geographically-challenged author of the article about Sinsabaugh linked above. Sinsabaugh's rural landscapes were definitely NOT taken in "Southern Illinois." They were taken in the vicinity of Champaign-Urbana, which is in east-central Illinois, in a part of the state once occupied by a gigantic grassland formerly known as the Grand Prairie, where one almost certainly would have been caught dead in a prairie fire. In this very long state, one isn't remotely beginning to get into Southern Illinois until one has gotten south of Springfield, which Campaign certainly is not. ]

Here are online versions of several of his landscape pictures, including many cropped to emphasize Illinois horizon lines:
Art Sinsabaugh | The Art Institute of Chicago

What you unfortunately cannot see in those tiny versions are the umpteen shades of grays in the original contact prints. I've never seen anything like that since.

**c.a.m** · 01-09-2021, 05:39 PM - **2 Likes**

Interesting topic. May I offer my perspective?

Corner Sharpness can be Crucial
While some types of images benefit from placing the subject at the centre of the frame, others are stronger when the subject is off-centre. For example, when I place a subject one-third in from an edge or corner, I want the subject to be sharp. Although sharpness at the extreme corners might not be necessary, lenses that are soft toward the edges and corners can be detrimental to this type of composition. I guess it depends on how we define "corner" and how much softness we can tolerate.

As mentioned by others, certain types of distributed subjects benefit from sharpness across the frame, such as landscapes, city scapes, buildings, or astrophotographs. In a landscape or city scape, I might choose to place a foreground object of interest near a bottom corner or the edge; for me, it's critical that the object is sharp in the image. Macro is another genre in which corner and edge sharpness can be important.

My subjects include all of the above genres as well as classic cars, machinery, nature, and wildlife.

My experience with the DA 18-135mm
I've had a DA 18-135mm lens for a number of years, and shot with it extensively and happily for a while. At the wider apertures or at focal lengths of 60-135mm, I found that the lens is considerably softer at the corners and borders than in the centre. Knowing the sharpness profile of the lens, I was being careful to limit my use to the 18-60mm focal lengths and apertures of f/5.6 to f/11.

Now, I tend to pair my DA 20-40mm Limited with my DA* 50-135. I find that these lenses are sharper across the frame and exhibit lower aberrations than the 18-135. Sometimes I need to swap lenses in the field, but working with only these two lenses minimizes lens choices and complexity, while not encumbering me with excessive weight. I'll also carry a DA 15mm Limited if I think I might need a wider angle than 20mm.

I would concede that the three lenses cost a lot more than a single DA 18-135, but the OP introduced this thread with a view on sharpness, not cost, weight, or other trade-offs. Nonetheless, the 18-135 is a convenient, low-cost, handy lens that is capable of producing very nice images -- if one doesn't need absolute sharpness in the corners or borders.

Pixel Peeping
The matter of pixel peeping seems to arise often when discussing corner sharpness, along the line of 'corner softness doesn't matter if one doesn't pixel peep'. Certainly, our technology allows us to zoom into images, reaching 100% or greater. I'll zoom in to full-scale or even 200% when I'm doing detailed post-processing steps, especially sharpening, adjusting local contrast, or selecting a demosaic scheme. Doing so allows me to exploit the tools to advantage and also to compare similar images in a sequence to select the best one.

Viewing our Images -- the ultimate test
In scenes or compositions where sharpness is important across the frame, I would contend that zooming in to 100% is a useful technique in the post-processing chain. However, when viewing an image normally, we're limited by the size of our monitor or a print. I use a 24-inch monitor (1920x1200 pixels), which displays images from my K-3 II at a 30% scale in full-screen. In most cases, moderate corner softness will not be overly apparent, if at all, and the images from the 18-135 appear fairly sharp (18-60mm focal lengths, stopped down). Aberrations, however, may be obvious but not dominant.

In a printed image, the apparent sharpness or softness will depend in part on how close one views the print: view it from a normal distance appropriate for the print's size, and don't 'zoom in' by putting your nose up to it!

- Craig

tibbitts · 01-09-2021, 06:17 PM - **1 Like**

Originally posted by goatsNdonkey

tibbits, could you say more about the kinds of lenses you employ to achieve really good corner, edge, and across the frame sharpness of the kinds you need. It sounds very interesting to me, and, also, it seems ***practical*** for a person know where they really need to go, in order to fulfill those kinds of requirements, rather than picking on consumer-level lenses which, even if good to very good, weren't made to go all the way there.

My only experience with digital is with Pentax, and as I've said it's been limited to what I can see with a 16mp sensor employing an aa filter. I've found the 60-250 is very consistent across the frame. Mine had AF that was substantially off when I bought it (new), but Pentax improved it under warranty. At the long end I still don't get consistently accurate viewfinder AF but live view almost always does well. The two Sigma EX macros I've used: 50mm and 70mm are also very good. AF isn't perfect with them either but I usually use MF for macro. None of those lenses has to be stopped down much or at all to provide sharp images across the frame. Stopped down just slightly, I've found the Sigma EX 17-50 also very good. I'm mostly happy with the Pentax 16-85 stopped down some - it does okay in most of its zoom range, but with close-distance subjects, on mine the left side is consistently weak at 16mm and the right side weak at 85mm. I don't observe the same problem with more distant subjects, although I'm not sure if that makes sense. I'd like a wide zoom with sharper edges than the 10-20mm Sigma EX (either version), although I have some photos taken with it that I like. I don't doubt the Pentax 11-18mm would be better (or the Sigma 8-16mm) but don't have either of those. The 8-16mm Sigma doesn't readily accept filters, and I do use a polarizer fairly often with the 10-20mm (not for skies, but to reduce reflections from foliage, and sometimes from water.)

LensBeginner · 01-10-2021, 05:33 AM - **1 Like**

One instance when corner sharpness, distortion and vignetting can be perceived is when you crop an image for framing: if the cropping is asymmetrical, your brain will perceive that resulting asymmetry in the distortion/sharpness/luminance pattern.
Probably the difference is only perceivable with a direct comparison though, and not much of an issue in the real world.

**othar** · 01-10-2021, 05:45 AM - **1 Like**

Originally posted by LensBeginner

One instance when corner sharpness, distortion and vignetting can be perceived is when you crop an image for framing: if the cropping is asymmetrical, your brain will perceive that resulting asymmetry in the distortion/sharpness/luminance pattern.
Probably the difference is only perceivable with a direct comparison though, and not much of an issue in the real world.

Are you suggesting you don't perfectly frame your shot everytime from the start

Distortion and vignetting can easily be corrected in post, but you are correct: what wasn't sharp from the beginning will never be

**RICHARD L.** · 01-10-2021, 06:01 AM

Thinking of it, one can carry a light zoom and have sharp corners too. I got a DFA 28-105 mm HD for my K1 and K3 and it never produces fuzzy corners.

K1 + DFA 28-105 HD

K3 + DFA 28-105 mm HD

The zoom range is not too large (about 4X) but the quality of the lens design is impressive.

normhead · 01-10-2021, 07:11 AM - **1 Like**

As I've said a million times....for portraits at 135mm, the soft edges make for smother bokeh yet the lens still has excellent sharpness in the centre, which is actually an advantage, reminiscent of the old days of portrait lenses. The DA 18-135 may have been the last of the "lenses for the way people take pictures, not for the test charts" lenses. The influence of the lens review community made this feature obsolete from a marketing stand point, if you want it, you have to buy the 18-135.

Media attacks on review sites and on this forum have not influenced it's owners however. You can attack whoever you want trying to make reputation for yourself, and way to many try and make their reputation by agreeing with what everyone else says. However, none of that changes the quality of the images and it just makes the critics look like fools.

It's rated excellent centre sharpness, at 17 different data points all through it range. There is not a setting where with care to use the lens to it's strength it can't produce an excellent image. Every image taken with this les will have excellent centre sharpness. Some people want to trade that for less centre sharpness, but better edge to edge. And that's not a problem, except for the part where those of us who like the lens the way it is have to listen to their incessant "but I don't like it."

lesmore49 · 01-10-2021, 09:47 AM

I maybe an aberration, but I have always liked my 18-135. I don't pixel peep the corners of photos...but I do pixel peep the center of the pix, where my subject invariably is located and I don't recall being unhappy with my 18-135's images. I find it very sharp, but then I don't tend to check out the extreme corners of my pix.

I'm more concerned about the subject of the photo...is it sharp, clear, etc.

As an aside, I will add....for airplane traveling where space and weight is a premium, my personal 3 amigo lenses that I carry are my 18-135, 55-300 and either my small 40 Limited or 70 Limited. These lenses, along with my K5, sans, battery grip for the trip...are my 'go to' travel kit.....when I want a good, lightweight variety. There you have it two 'consumer' Ienses (18-135, 55-300), and one Limited prime.....what else do I need .

normhead · 01-10-2021, 10:08 AM

Originally posted by lesmore49

I maybe an aberration, but I have always liked my 18-135. I don't pixel peep the corners of photos...but I do pixel peep the center of the pix, where my subject invariably is located and I don't recall being unhappy with my 18-135's images. I find it very sharp, but then I don't tend to check out the extreme corners of my pix.

I'm more concerned about the subject of the photo...is it sharp, clear, etc.

As an aside, I will add....for airplane traveling where space and weight is a premium, my personal 3 amigo lenses that I carry are my 18-135, 55-300 and either my small 40 Limited or 70 Limited. These lenses, along with my K5, sans, battery grip for the trip...are my 'go to' travel kit.....when I want a good, lightweight variety. There you have it two 'consumer' Ienses (18-135, 55-300), and one Limited prime.....what else do I need .

I was thinking, I have one photo that is actually ruined by the DA 18-135, where I misguidedly took a landscape at 135mm. . I looked for it as an example, but then I thought, "Would that be fair if I didn't post the thousands of successful photos?"

I have no need to provide ammunition for the nay sayers.

lesmore49 · 01-10-2021, 10:49 AM

The only issue I have with my 18-135 is that the zoom creeps downward when I carry the camera and the camera/lens is pointed downward.

I don't think this is unusual with this lens. Was it a big enough deal for me to return to sender ? Nope and I've had this lens for 6-7 years or so. Serves me well as an image producer and yes, the zoom creep is still there.

To OP. I think you will find this lens a great addition and a lens that you will find versatile, light to carry and that you will get some excellent photos from this moderate wide angle to moderate telephoto zoom over the years. Good decision to get it.

**goatsNdonkey** · 01-10-2021, 01:41 PM

Here's a case where I got better edge sharpness in a shot without particularly trying to, using my manual Phoenix/Samyang f/4-4.5 18-28mm. I probably posted the aperture & maybe the focal length chosen, if I posted this picture before, but couldn't tell you now. The corners look a bit soft, but considering how I was focused on the clock face of the building, how sharp some of the foreground branches look near the top and bottom edges is a bit surprising. If I was a stickler, I would want to redo a shot like this using lenses/techniques like those used by tibbets.

01-09-2021, 05:39 PM - 2 Likes	#21
c.a.m Site Supporter Join Date: Jan 2013 Location: Ottawa, Canada Photos: Gallery \| Albums Posts: 4,191	Corners, edges, pixels, and viewing Interesting topic. May I offer my perspective? Corner Sharpness can be Crucial While some types of images benefit from placing the subject at the centre of the frame, others are stronger when the subject is off-centre. For example, when I place a subject one-third in from an edge or corner, I want the subject to be sharp. Although sharpness at the extreme corners might not be necessary, lenses that are soft toward the edges and corners can be detrimental to this type of composition. I guess it depends on how we define "corner" and how much softness we can tolerate. As mentioned by others, certain types of distributed subjects benefit from sharpness across the frame, such as landscapes, city scapes, buildings, or astrophotographs. In a landscape or city scape, I might choose to place a foreground object of interest near a bottom corner or the edge; for me, it's critical that the object is sharp in the image. Macro is another genre in which corner and edge sharpness can be important. My subjects include all of the above genres as well as classic cars, machinery, nature, and wildlife. My experience with the DA 18-135mm I've had a DA 18-135mm lens for a number of years, and shot with it extensively and happily for a while. At the wider apertures or at focal lengths of 60-135mm, I found that the lens is considerably softer at the corners and borders than in the centre. Knowing the sharpness profile of the lens, I was being careful to limit my use to the 18-60mm focal lengths and apertures of f/5.6 to f/11. Now, I tend to pair my DA 20-40mm Limited with my *DA 50-135. I find that these lenses are sharper across the frame and exhibit lower aberrations than the 18-135. Sometimes I need to swap lenses in the field, but working with only these two lenses minimizes lens choices and complexity, while not encumbering me with excessive weight. I'll also carry a DA 15mm Limited if I think I might need a wider angle than 20mm. I would concede that the three lenses cost a lot more than a single DA 18-135, but the OP introduced this thread with a view on sharpness, not cost, weight, or other trade-offs. Nonetheless, the 18-135 is a convenient, low-cost, handy lens that is capable of producing very nice images -- if one doesn't need absolute sharpness in the corners or borders. Pixel Peeping** The matter of pixel peeping seems to arise often when discussing corner sharpness, along the line of 'corner softness doesn't matter if one doesn't pixel peep'. Certainly, our technology allows us to zoom into images, reaching 100% or greater. I'll zoom in to full-scale or even 200% when I'm doing detailed post-processing steps, especially sharpening, adjusting local contrast, or selecting a demosaic scheme. Doing so allows me to exploit the tools to advantage and also to compare similar images in a sequence to select the best one. Viewing our Images -- the ultimate test In scenes or compositions where sharpness is important across the frame, I would contend that zooming in to 100% is a useful technique in the post-processing chain. However, when viewing an image normally, we're limited by the size of our monitor or a print. I use a 24-inch monitor (1920x1200 pixels), which displays images from my K-3 II at a 30% scale in full-screen. In most cases, moderate corner softness will not be overly apparent, if at all, and the images from the 18-135 appear fairly sharp (18-60mm focal lengths, stopped down). Aberrations, however, may be obvious but not dominant. In a printed image, the apparent sharpness or softness will depend in part on how close one views the print: view it from a normal distance appropriate for the print's size, and don't 'zoom in' by putting your nose up to it! - Craig Last edited by c.a.m; 01-10-2021 at 07:49 AM. Reason: clarity

01-10-2021, 06:01 AM	#25
RICHARD L. Loyal Site Supporter Join Date: Oct 2018 Location: Quebec City, Quebec Posts: 6,623	Thinking of it, one can carry a light zoom and have sharp corners too. I got a DFA 28-105 mm HD for my K1 and K3 and it never produces fuzzy corners. K1 + DFA 28-105 HD K3 + DFA 28-105 mm HD The zoom range is not too large (about 4X) but the quality of the lens design is impressive. Last edited by RICHARD L.; 01-10-2021 at 05:14 PM.

01-10-2021, 07:11 AM - 1 Like	#26
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	As I've said a million times....for portraits at 135mm, the soft edges make for smother bokeh yet the lens still has excellent sharpness in the centre, which is actually an advantage, reminiscent of the old days of portrait lenses. The DA 18-135 may have been the last of the "lenses for the way people take pictures, not for the test charts" lenses. The influence of the lens review community made this feature obsolete from a marketing stand point, if you want it, you have to buy the 18-135. Media attacks on review sites and on this forum have not influenced it's owners however. You can attack whoever you want trying to make reputation for yourself, and way to many try and make their reputation by agreeing with what everyone else says. However, none of that changes the quality of the images and it just makes the critics look like fools. It's rated excellent centre sharpness, at 17 different data points all through it range. There is not a setting where with care to use the lens to it's strength it can't produce an excellent image. Every image taken with this les will have excellent centre sharpness. Some people want to trade that for less centre sharpness, but better edge to edge. And that's not a problem, except for the part where those of us who like the lens the way it is have to listen to their incessant "but I don't like it." Last edited by normhead; 01-10-2021 at 07:25 AM.

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01-09-2021, 02:02 PM	#16
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006	Originally posted by robgski I agree, the life of a pixel-peeper must be dreary and disappointing. my DA 18-135mm WR is a keeper Disappointing, frustrating and never to be satisfied, I guess. I'll never let myself go there.

01-09-2021, 02:43 PM	#17
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	In the digital era we can simulate inadequate edge/corner performance pretty easily. We can't simulate adequate edge/corner performance. Images can be "sharpened" but that doesn't create detail that wasn't there to start with. I'm not really that hard-core about sharpness - my cameras are 16mp with aa filters, and sometimes I use (horrors!) f16 (or smaller!), which should be severely diffraction-limited on crop sensors. Still many of the lenses I have or have had are are just obviously not sharp across the frame, even stopped down to f8 or f11 etc. Some of were okay in the 6mp era but not now.

01-09-2021, 02:46 PM - 1 Like	#18
goatsNdonkey Site Supporter Join Date: Jan 2016 Location: Fulton County, Illinois Posts: 3,736 Original Poster	Originally posted by photoptimist @goatsNdonkey covered most of the key dimensions of the debate. Yes, some shots for some types of photographic genres (astro, art/archival reproduction, architecture, and landscape) do benefit from corner-to-corner sharpness. And most other photos work beter with central sharpness and edge/corner softness (either due to the lens or bokeh/out-of-focus conditions). One big factor that can favor of soft-corner-lenses in almost all genres of photography is that sharp-corner lenses tend to be large, expensive, and have limited or no zoom. For on-the-go photography on a budget or with weight constraints, a lens such as the 18-135 WR is far far superior to a bag full of sharper lenses. In the realm of travel and hiking photography, the photographer with a single light-weight zoom will get more shots of more different subjects than the photographer who was burdened by carrying and swapping a bunch of heavy, sharp lenses. Sometimes it's better to have a soft-corner image than no image at all because the sharp-corner-lenses were too expensive, too heavy to carry on a trip/hike, or took too long to swap. Also, there are so many lenses that get better corner sharpness closed down a couple of stops, and, if a zoom, zoomed in or out from its extremes where the most design compromises have been made--consequently a lens that can give soft corners, might be employed in ways that give acceptable corner sharpness for many if not all images. It does help to really know how to use a particular lens and how to get it to rise above its limitations.

01-09-2021, 02:53 PM	#19
goatsNdonkey Site Supporter Join Date: Jan 2016 Location: Fulton County, Illinois Posts: 3,736 Original Poster	Originally posted by tibbitts In the digital era we can simulate inadequate edge/corner performance pretty easily. We can't simulate adequate edge/corner performance. Images can be "sharpened" but that doesn't create detail that wasn't there to start with. I'm not really that hard-core about sharpness - my cameras are 16mp with aa filters, and sometimes I use (horrors!) f16 (or smaller!), which should be severely diffraction-limited on crop sensors. Still many of the lenses I have or have had are are just obviously not sharp across the frame, even stopped down to f8 or f11 etc. Some of were okay in the 6mp era but not now. tibbits, could you say more about the kinds of lenses you employ to achieve really good corner, edge, and across the frame sharpness of the kinds you need. It sounds very interesting to me, and, also, it seems *practical* for a person know where they really need to go, in order to fulfill those kinds of requirements, rather than picking on consumer-level lenses which, even if good to very good, weren't made to go all the way there.

01-09-2021, 03:20 PM	#20
goatsNdonkey Site Supporter Join Date: Jan 2016 Location: Fulton County, Illinois Posts: 3,736 Original Poster	Art Sinsabaugh got pretty good edge and corner sharpness in the contact prints he took from negatives made with his 12x20 inch banquent camera. I saw framed contact prints up close when he came to visit one of my classes at Monmouth College in the early 1970s. Here's an article about him: ART SINSABAUGH: “Life on the Road: Art Sinsabaugh’s Midwest Landscapes” (2005) – AMERICAN SUBURB X [ CORRECTION for the geographically-challenged author of the article about Sinsabaugh linked above. Sinsabaugh's rural landscapes were definitely NOT taken in "Southern Illinois." They were taken in the vicinity of Champaign-Urbana, which is in east-central Illinois, in a part of the state once occupied by a gigantic grassland formerly known as the Grand Prairie, where one almost certainly would have been caught dead in a prairie fire. In this very long state, one isn't remotely beginning to get into Southern Illinois until one has gotten south of Springfield, which Campaign certainly is not. ] Here are online versions of several of his landscape pictures, including many cropped to emphasize Illinois horizon lines: Art Sinsabaugh \| The Art Institute of Chicago What you unfortunately cannot see in those tiny versions are the umpteen shades of grays in the original contact prints. I've never seen anything like that since.

01-09-2021, 06:17 PM - 1 Like	#22
tibbitts Pentaxian Join Date: Apr 2007 Location: Oklahoma USA Posts: 2,196	Originally posted by goatsNdonkey tibbits, could you say more about the kinds of lenses you employ to achieve really good corner, edge, and across the frame sharpness of the kinds you need. It sounds very interesting to me, and, also, it seems *practical* for a person know where they really need to go, in order to fulfill those kinds of requirements, rather than picking on consumer-level lenses which, even if good to very good, weren't made to go all the way there. My only experience with digital is with Pentax, and as I've said it's been limited to what I can see with a 16mp sensor employing an aa filter. I've found the 60-250 is very consistent across the frame. Mine had AF that was substantially off when I bought it (new), but Pentax improved it under warranty. At the long end I still don't get consistently accurate viewfinder AF but live view almost always does well. The two Sigma EX macros I've used: 50mm and 70mm are also very good. AF isn't perfect with them either but I usually use MF for macro. None of those lenses has to be stopped down much or at all to provide sharp images across the frame. Stopped down just slightly, I've found the Sigma EX 17-50 also very good. I'm mostly happy with the Pentax 16-85 stopped down some - it does okay in most of its zoom range, but with close-distance subjects, on mine the left side is consistently weak at 16mm and the right side weak at 85mm. I don't observe the same problem with more distant subjects, although I'm not sure if that makes sense. I'd like a wide zoom with sharper edges than the 10-20mm Sigma EX (either version), although I have some photos taken with it that I like. I don't doubt the Pentax 11-18mm would be better (or the Sigma 8-16mm) but don't have either of those. The 8-16mm Sigma doesn't readily accept filters, and I do use a polarizer fairly often with the 10-20mm (not for skies, but to reduce reflections from foliage, and sometimes from water.)

01-10-2021, 05:33 AM - 1 Like	#23
LensBeginner Veteran Member Join Date: Sep 2014 Photos: Albums Posts: 4,696	One instance when corner sharpness, distortion and vignetting can be perceived is when you crop an image for framing: if the cropping is asymmetrical, your brain will perceive that resulting asymmetry in the distortion/sharpness/luminance pattern. Probably the difference is only perceivable with a direct comparison though, and not much of an issue in the real world.

01-10-2021, 05:45 AM - 1 Like	#24
othar Site Supporter Join Date: May 2014 Location: Linz Photos: Albums Posts: 3,098	Originally posted by LensBeginner One instance when corner sharpness, distortion and vignetting can be perceived is when you crop an image for framing: if the cropping is asymmetrical, your brain will perceive that resulting asymmetry in the distortion/sharpness/luminance pattern. Probably the difference is only perceivable with a direct comparison though, and not much of an issue in the real world. Are you suggesting you don't perfectly frame your shot everytime from the start Distortion and vignetting can easily be corrected in post, but you are correct: what wasn't sharp from the beginning will never be

01-10-2021, 09:47 AM	#27
lesmore49 Pentaxian Join Date: Nov 2007 Location: Western Canada Posts: 12,349	I maybe an aberration, but I have always liked my 18-135. I don't pixel peep the corners of photos...but I do pixel peep the center of the pix, where my subject invariably is located and I don't recall being unhappy with my 18-135's images. I find it very sharp, but then I don't tend to check out the extreme corners of my pix. I'm more concerned about the subject of the photo...is it sharp, clear, etc. As an aside, I will add....for airplane traveling where space and weight is a premium, my personal 3 amigo lenses that I carry are my 18-135, 55-300 and either my small 40 Limited or 70 Limited. These lenses, along with my K5, sans, battery grip for the trip...are my 'go to' travel kit.....when I want a good, lightweight variety. There you have it two 'consumer' Ienses (18-135, 55-300), and one Limited prime.....what else do I need .

01-10-2021, 10:08 AM	#28
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by lesmore49 I maybe an aberration, but I have always liked my 18-135. I don't pixel peep the corners of photos...but I do pixel peep the center of the pix, where my subject invariably is located and I don't recall being unhappy with my 18-135's images. I find it very sharp, but then I don't tend to check out the extreme corners of my pix. I'm more concerned about the subject of the photo...is it sharp, clear, etc. As an aside, I will add....for airplane traveling where space and weight is a premium, my personal 3 amigo lenses that I carry are my 18-135, 55-300 and either my small 40 Limited or 70 Limited. These lenses, along with my K5, sans, battery grip for the trip...are my 'go to' travel kit.....when I want a good, lightweight variety. There you have it two 'consumer' Ienses (18-135, 55-300), and one Limited prime.....what else do I need . I was thinking, I have one photo that is actually ruined by the DA 18-135, where I misguidedly took a landscape at 135mm. . I looked for it as an example, but then I thought, "Would that be fair if I didn't post the thousands of successful photos?" I have no need to provide ammunition for the nay sayers.

01-10-2021, 10:49 AM	#29
lesmore49 Pentaxian Join Date: Nov 2007 Location: Western Canada Posts: 12,349	The only issue I have with my 18-135 is that the zoom creeps downward when I carry the camera and the camera/lens is pointed downward. I don't think this is unusual with this lens. Was it a big enough deal for me to return to sender ? Nope and I've had this lens for 6-7 years or so. Serves me well as an image producer and yes, the zoom creep is still there. To OP. I think you will find this lens a great addition and a lens that you will find versatile, light to carry and that you will get some excellent photos from this moderate wide angle to moderate telephoto zoom over the years. Good decision to get it.

01-10-2021, 01:41 PM	#30
goatsNdonkey Site Supporter Join Date: Jan 2016 Location: Fulton County, Illinois Posts: 3,736 Original Poster	Here's a case where I got better edge sharpness in a shot without particularly trying to, using my manual Phoenix/Samyang f/4-4.5 18-28mm. I probably posted the aperture & maybe the focal length chosen, if I posted this picture before, but couldn't tell you now. The corners look a bit soft, but considering how I was focused on the clock face of the building, how sharp some of the foreground branches look near the top and bottom edges is a bit surprising. If I was a stickler, I would want to redo a shot like this using lenses/techniques like those used by tibbets.