[y0chang]

donut bokeh is different than onion ring bokeh, wonder if its because the edges are over corrected which causes the outlining

[FabioPirovano]

Any Pentax Lenses is far better... period

[Quicksand]

Hey, a lens can't feasibly correct for absolutely everything. Especially not a zoom!

Some lenses have strange distortions (DA 21, I'm looking at you). Some have uncorrected CA or have excessive fringing (FA 77, as much as I love it). Some are sharp in the middle and less so around the edges (DA 15). Some exhibit more field curvature than others (DA 15 again). Some have a lot of coma (Oh hi, Cosina 55/1.2). Some (ok, probably all) lenses vignette to some extent. Some will flare if you even think about bright light (Sigma 24-60/2.8). Some are big, some small, some slow, some fast, some cool, some warm. And yeah, some have weird bokeh.

This Sigma 18-35 gets a lot of things right. But not everything! For some, this lens will be a fine choice. For me, meh. I like primes.

[Digitalis]

I don't know how you'll take this, but I think your example perfectly illustrates why it's pretty much a non-issue for me.

Would you like me to send my copy of the 18-35mm f/1.8 and see if you can use this lens for a month without hating it? To me this is a crippling fault. Stopping the lens down does not eliminate it.

It is even visible at longer focal lengths:


Pentax K5IIS - Sigma 18-35mm f/1.8@ 35mm f/1.8 - full frame.

And all of this pre-supposes that the bokeh circle is even visible or noticeable under normal viewing circumstances.

The rings are visible, even at web display sizes.

Maybe there are some unintended internal reflections going on.

Unlikely, if there was an internal reflection it would be affecting the entire image, not the bokeh. My hypothesis is that the first element aspheric lens has a unique curvature* this could be the cause of the rings as the geometry of the lens will bend off axis light in unintended ways.

That's some real pixel peeping noticing that.

50% magnification is hardly pixel peeping.

* I have seen a lot of aspheric lenses in my life, but the one used as the first element in the Sigma 18-35mm f/1.8 is unusual.

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Last edited by Digitalis; 12-04-2014 at 06:10 PM.

[Edgar_in_Indy]

The rings are visible, even at web display sizes.

I had to play "Where's Waldo" for a minute to find the rings in the last picture, so I guess you're probably more sensitive to them and aware of them than I am. I think most people would simply see a wonderfully photographed picture of lovely blossoms. But if it's your lens, and they bother you (or your clients), then it's a problem.

BTW, the sample pictures you post are always beautiful, even the "bad" ones.

[Digitalis]

The funny things it my clients did notice the difference with the sigma lens, they are accustomed to the Zeiss, Voigtlander, Pentax and Leica lenses I usually use for commercial work. One of my long term clients said the images from the sigma looked colder and the out of focus areas had a harsher look to them.

This reflects my opinion when I compared the SMCP-FA 31mm f/1.8 to the Sigma 18-35mm f/1.8 - the FA31 wipes the floor with the sigma lens when it comes to bokeh rendering, CA is higher on the pentax lens - and when both lenses are stopped down the FA31 maintains a healthy lead in terms of resolution and overall image quality. The sigma lens is good - but it really can't compete with the consistent image quality that can be achieved through using primes.

[freerider]

I took a close look at several photos taken with my copy and can't say that I see any donut bokeh.

[Digitalis]

I took a close look at several photos taken with my copy and can't say that I see any donut bokeh.

Try using the lens with longer focusing distances, about 1m~2m at wider apertures rather than pure close ups. You will see it.

The bokeh from the 18-35mm f/1.8 is just nasty when directly compared to the FA31:


Left: Sigma 18-35mm f/1.8 @ 31mm f/1.8 - Right: Pentax FA31 @ f/1.8 - both lenses are set at a 5m focus distance.

[mee]

I took a close look at several photos taken with my copy and can't say that I see any donut bokeh.

Was there any processing on those? Lots of contrast and color.. very rich and sharp.

[freerider]

Try using the lens with longer focusing distances, about 1m~2m at wider apertures rather than pure close ups. You will see it.

The bokeh from the 18-35mm f/1.8 is just nasty when directly compared to the FA31:

I'll cruise through some more shots and see if I can find any examples of distance bokeh. I agree with you regarding the 31mm, though. There is no comparison. The bokeh on the 31mm is much, much nicer IMO.

Was there any processing on those? Lots of contrast and color.. very rich and sharp.

Nope, no post processing on those.

[Edgar_in_Indy]

Here's the post-processed version:



I tweaked the colors to taste, and applied a touch of sharpening to help the details pop. Total correction time was under two minutes, and that includes adding the vignetting and the lens flare. The original doesn't look so good anymore, huh?

[deadwolfbones]

lol

[Digitalis]

*my eyes*

[dave sz]

Try using the lens with longer focusing distances, about 1m~2m at wider apertures rather than pure close ups. You will see it.

The bokeh from the 18-35mm f/1.8 is just nasty when directly compared to the FA31:


Left: Sigma 18-35mm f/1.8 @ 31mm f/1.8 - Right: Pentax FA31 @ f/1.8 - both lenses are set at a 5m focus distance.

Can't disagree with that.

[Texdance]

I find it funny, and kind of sad, that this is the fastest wide angle AF lens available for Pentax, and it's a zoom. Pentax, where are my fast, wide angle (preferably WR) primes?

They are back in the manual focus history of Pentax and some early AF lenses without chips.
Just off the top of my head, and weak on some whith wich I am not familiar:


K 15 /f? and 15 Fisheye, and I think there was an 18mm in there somewhere.
M 20/f4
F 24-50/f4 AF
A 35/f2,
M, K and F and FA 50/f1.2 and 50f1.4 and one of the best lenses for the money ever the 50f2.
M 85/2
M, A, F, FA,100/2.8 Macro, several MF and AF versions
A 135/1.8 a great lens that was too heavy and too costly to be useful.
M 200/2.5 add the AF 1.7 Adapter for a 340mm/f 4.3 semi-AF lens.
A 200/4 Macro, and successor FA both great lenses . At 1:1 MF too long, but still great even using 1.7x AF Adapter.
A 70/210/f4 and the not-so-great kit-like F 70-210/f4-5.6
F 300/4 oh what a fine lens that was, the original off-white version with the big handle / rotating tripod collar.
...and the surprisingly affordable Pentax 600/f4 though the lack of AF extenders was always a problem for me in actual use. But with the advent of the digital 1.5x crop factor, my 600/4 was actually too long for many wildlife and birding shots and I had to use my Pentax M 200/2.5 with AF Adapter 1.7x, or Nikon AF 300/4 EDIF instead.

"Fast" has become a term closely affected by the increasingly high ISO available that gives acceptable photo quality. When 800 and 1600 and even 3200-6400 ISO are available, an f2.8 and even F4 lens provides good light-gathering and decent bokeh. Can't say the same for f5.6 and f6.3 apertures in terms of blurring the background.

When a full-frame camera re-appears everything will change again. Those xx-300mm and 400mm and even 600mm lenses will again be too short for the full gamut of wildlife photography (which btw now requires a full range of remotely controllable bodies, flashes, and accessories - and video imaging capability - to get pro photos of the highest order).

Now, if you want something faster than f5.6, it seems you are either A. out of luck or B. need to spend $1000-$1500 or more, or C. hope Tamron, Sigma, others eventually have mercy on Pentax users and add that mount, despite the small market.

I almost gave up on Pentax shortly after they went digital. The Pz1P cost $500 ($400 on sale, maybe $750 today's dollars) and was the very best user friendly film camer a ever, but somehow Pentax now Ricoh manages to shoot itself in the foot time and again in the digital market, making overpriced almost-great cameras that a few inexpensive add-ons could turn into great cameras.

Where are the world-beater $700-900 cameras and $200-300 prime lenses with all the bells and whistles, there is no reason they can't be done with the low labor and robot manufacturing costs and chip costs available now. Just quit with all the market segmentation and make us one good no great camera and lens set (five primes, four zooms, all similar components, maybe two filter sizes, re-use internal elements for more than one lens, same with controls and maybe even shells) and be sure to make it a full frame 35mm with lots of resolution so the guys with only short 300mm lens can still blow up a crop to make an occasional bird or wildlife photo.

If you make it, they will come.