[philbaum]

I think there is a sort of "tyranny of focus" out there that implies the only good images are sharp across the image, and thereby implying the only good lenses are sharp across the lens. Witness the obsessive reporting of sharpness of center, edges and extreme edges.

Its not that i'm opposed to that kind of photography, but i'm begining to appreciate the more "impressionistic" type of photography where images imply but don't explicity show details overall. for one thing, you don't always want to show background faces that aren't part of the story, or may require you to get permission to publish. Also, customers don't usually want to see someone elses face in their living room if they purchase your art.

This is the kind of image that intrigues me in the last few weeks: (it was taken with a DA-35 ltd at F4, but taken close enough to provide blurring in non critical areas)


Restforwearysouls-5648 by philnw, on Flickr

To me, the subject is about the attractive sidewalk bench, and the viewer doesn't need to see the detail of the faces of the musicians sitting on the sidewalk, or store detail in the background.

Yet another image, FA50 @f3.2,




What got me thinking like this is the ongoing discussion thread on the Sigma 30 f1.4 which has somewhat softer edges, but excellent center sharpness, fast focusing, and 3-d appearance. In short, a flat focus field is not all that desirable when it compromises on rendering qualities such as high contrast properties that lead to fast focusing.

Anyway, i'm appreciating bokeh more and tons of focused details less - nice change of pace.

[Andrew Lang]

i rarely take pics with an aperture above 4 or 5.6 most of my shots are 1.4 on my 50 and 2.8 on my 16-50

[SpecialK]

Witness the obsessive reporting of sharpness of center, edges and extreme edges.

Eh, I think that refers to the lens and not the image. Plenty of selective focus images out there, so you must be looking in the wrong place :-)

[philbaum]

Eh, I think that refers to the lens and not the image. Plenty of selective focus images out there, so you must be looking in the wrong place :-)

Of course it refers to the lens. What is the first thing new buyers are encouraged to do when they buy a lens - shoot a brick wall or a newspaper . Part of my small rant was my own self imposed standards which i'm now taking a happy break from. But our concern over lenses, often caries over to our pixel peeping of our images (of course, not all images)

[Laurentiu Cristofor]

Well, do you think the shots you posted would still work if the in-focus parts were unsharp? In both images, the focused parts are next to the borders. If you would have a defocused background and an unsharp foreground then there wouldn't be much left to impress you in those shots.

[Adam]

It all depends on what you are trying to shoot and for what purpose. Photos for a textbook would probably need to be sharp from corner to corner, while photos to hang on your wall or anything artistic would benefit more from the use of DOF and bokeh.

[pop4]

Might I suggest the OP have a look at the https://www.pentaxforums.com/forums/mini-challenges-games-photo-stories/93874...our-bokeh.html thread? Not everyone's obsessed about edge-to-edge shallow-to-deep focus!

[JinDesu]

If I bought a lens exclusively for portraits, I wouldn't care if it had sharp edges/corners. So for example, the Sigma 30 1.4 would be an example of that. If, however, I may use the lens for anything else, then I would want the edge and corners to be at least good.

[sterretje]

The images that you show are all about DOF and not about edge/corner sharpness. As Laurentiu Cristofor (and JinDesu) indicate, this will not be possible with a lens with bad corner / edge performance.

But welcome to the world of shallow DOF; use it to your advantage

[RonHendriks1966]

Well it is true that there is more need for sharpness to get appriciation for pictures these days I think.

Now am I a sharpness all over freak (at least where it comes to the main subject of the picture), but I do love something nice in the bokeh.

[Rondec]

It just really depends on the photo, doesn't it? There are some amazing landscape photos (done with photo stacking I suppose) which have everything in focus. There are plenty of others where only a flower, say, is truly in focus.

I do think that there is over emphasis placed on edge performance, specs of a lens. When the DA 18-135 was released and tested by Photozone, it seemed to get castigated for poor performance, but I have seen plenty of great shots from it. The question is more how a lens works for you and whether you can avoid its weaknesses and emphasize its strengths. The Sigma 30 is another good example. A good lens that has somewhat weak corners, but still works beautifully in practice.

[hoanpham]

One of the soft wide open i have now is the Petri 28/2.8. Sharp half click down, very sharp at 5.6.
Photos on my picasa. Interesting lens.

[philbaum]

It just really depends on the photo, doesn't it? There are some amazing landscape photos (done with photo stacking I suppose) which have everything in focus. There are plenty of others where only a flower, say, is truly in focus.

I do think that there is over emphasis placed on edge performance, specs of a lens. When the DA 18-135 was released and tested by Photozone, it seemed to get castigated for poor performance, but I have seen plenty of great shots from it. The question is more how a lens works for you and whether you can avoid its weaknesses and emphasize its strengths. The Sigma 30 is another good example. A good lens that has somewhat weak corners, but still works beautifully in practice.

Rondec and similar commenters;
I phrased my original post badly; i think there is a place for all these techniques: photo stacking, bokeh enthusiasts, etc. What i'm discovering for myself, is a new enjoyment of the blurred/bokeh areas and their use in an image. Its not that i will never make an edge to edge (hopefully sharpish) image.

What i don't think is well understood by many of us, is that there are tradeoffs in lens designs, e.g. one can get superlative edge to edge sharpness, but lack richness and contrast in colors, or have dreaded CA's, or "mustache" edges in UWA lenses. There are some posters in this forum that seem to have significant knowledge in lens designs, and when one sees comments from these folks in threads such as the Sigma 30 thread, its a valuable learning situation. Instead of looking at the DA-21 and Sigma 30 as being deficient in edge to edge sharpness compared to their "peers", the truth is that they've been optimized for different optical qualities than the "average" lens. No single lens is going to excel in all optical parameters. And some reviewers don't seem to "get" that lenses can be optimized in different ways; that doesn't make them deficient, just different. Thats what i've learned from reading PF.

[reeftool]

The reason we desire sharp lenses is because it is quite easy to get a soft image from any lens but impossible to get a sharp image from a crappy one. There have been special soft focus lenses manufactured through the years, mostly intended for portraits. There are also soft focus filters made for this purpose. While looking through lens reviews, often some of the sharpest are also said to have the best bokeh also. What we consider pleasing bokeh is also a matter of personal preference. Choosing the right focal length for the shot is important too. If you want the background to disappear, shoot with a long lens.

[newarts]

Some of us are more subject oriented than others. I like full face portraits, macros where the subject dominates the photo, etc - in many of my photos edge sharpness doesn't matter or can detract from my purpose.

A good case in point is the use of the Raynox close-up lens for macros; here's a nice macro posted here recently by Beregeded:

https://www.pentaxforums.com/forums/lens-clubs/74221-raynox-macro-club-23.html#post1709155

Looks great to me! But here's a test showing the edge sharpness for a Raynox 150 on a good Macro lens (Tamron 90:2.5):

Without the Raynox 150, the edges of the photo are just as sharp as the center. with the Raynox the edges and corners are poor. The top-most of the crops shows the upper-left quadrant of the full photo... Notice the in-focus area is in a disk about equal to the frame height.

But this is the sharpness distribution for the lens used to take the macro posted above - clearly the edge softness inherent in using the Raynox had no practical effect.

Edge quality matters a lot for wide angle lenses - one of the main reasons to use a wide angle lens is to see what's at the edges of a scene - otherwise why use a wide angle lens?