[sjyoon20904]

I just bought sigma 18 35 1.8. Pictures even sharp at 1.8 pretty amazing lens.

FA 31 at 1.8




Sigma 18 35

[starjedi]

I just bought sigma 18 35 1.8. Pictures even sharp at 1.8 pretty amazing lens.

FA 31 at 1.8




Sigma 18 35

It seems that sigma 18-35 becomes popular... A great lens..

[Paul the Sunman]

Not sure what your Sigma was focussed on. The whole thing looks out of focus to me.

[sjyoon20904]

Yeah, it does have some problem focusing.

I think it's focused right at the knife blade meets butter.

Picture taken very closed to the subject at 35mm. So it has very, very shallow dof.

I do like macro-ability of sigma over FA31.

[MadMathMind]

You really need to calibrate the Sigma if you're going to do close shots where DoF matters. I never noticed an issue with my lens until I started doing that. I haven't had problems at small apertures or even at large apertures shooting things that are far away, but close shots at large apertures...it is seemingly a crapshoot. It took me almost a year and a few thousand shots to find this out. I didn't see the issues the reviewers cited probably because I didn't test all scenarios and perhaps I just got lucky to get a copy that does work for most of what I want to shoot with it.

I will, of course, continue to use the Sigma because it is *really* sharp. It does objects well. Part of that is that you can take your time with things that don't move and get the focus right. With people...well, they get impatient.

[Paul the Sunman]

The bokeh is attractive, but even at the sharpest point, it doesn't seem perfectly focussed to me. What was your exposure time? Did you use a tripod?

Interesting subject; never shot butter before.

[Driline]

Pictures even sharp at 1.8 pretty amazing lens.

Digitalis will tell you otherwise.

[sjyoon20904]

Handheld at 1/60th sec. iso 200 at 35mm

center part cropped



I'm definitely getting sigma dock next week for fine tuning. It'll be another $59 dollars. But I think this lens is bargain at $799.

Buy it, Buy it, Buy it

[MadMathMind]

Digitalis will tell you otherwise.

Not quite. Digitalis will tell you that when it focuses, it's really sharp. He will also tell you that the bokeh is inconsistent and can be really great or really bad.
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/270250-pent...m-f-1-8-a.html

His summary is:

Even with these issues the Sigma 18-35mm f/1.8 Is an extremely good lens. The issues I have pointed out are things to be aware of and can be avoided to a certain extent. Personally I would have no issue with recommending the Sigma 18-35mm f/1.8 to another experienced photographer who would be able to make the most of its strengths, and be aware of its weaknesses and find their own way around them. However I wouldn’t recommend this lens to someone starting out with photography as the weight and focusing issues would be discouraging to someone who isn't familiar with wide aperture lenses.

Now that I've had it for almost a year, I agree with his assessment. There are some wonderful things about the Sigma. It is, however, difficult to use because it can be quirky. One thing, though, is that if you are inexperienced and want to learn, this lens will teach you a lot. The cost will be a lot of poor photographs, so as long as you're not learning this stuff on a once-in-a-lifetime vacation, I don't share his hesitance of recommending it to a beginner. Ok, true beginner, that would be bad. Someone with modest experience can benefit from the lens's issues, as it will teach you a lot about analyzing strengths and weaknesses of a lens.

Anyway, there's a number of threads on this topic:
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/277499-sigm...es-thread.html
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/293402-sigm...xperience.html
https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/289009-re-t...e-18-35-a.html


And sjyoon2094, your lens is definitely not focusing right. When the lens focuses perfectly, the sharpness is almost hyperreal:


Download the 100% version of this photo and pixel peep it. It is utterly unbelievable. And this is blurred and smoothed a bit because you could see the pores on her face. It was actually unflattering...

Here it is a 1.8. Again, try pixel peeping this one.

[sjyoon20904]

I would have to agree with you, MadMathMind.
This lens does have some weird focusing problem, and I'm willing to explore more on this issue.
My point here is that IF it's in focus, I think sigma is sharper at the center than FA 31 at 1.8.
Don't get me wrong, I still love my FA31.

[Stavri]

That the art 18-35/f1.8 is a sharp lens wide open is not news. It's sharper than the Sgima Art 30/f1.4 prime to put things in perspective. It has the AF issues (needs a dock to cut down on AF inconsistencies) and the "frogegg" bokeh is present under high specular backgrounds, but as far as image quality when you nail the focus is almost unparallelled.

Everyone familiar with its built in "macro" function?
@f2.8

[hjoseph7]

I just bought sigma 18 35 1.8. Pictures even sharp at 1.8 pretty amazing lens.

FA 31 at 1.8




Sigma 18 35

The Sigma picture is much larger than the 31mm ?

[sjyoon20904]

Okay, I've been playing around with sigma dock for a while.
I did ran in to a problem.
Now it focuses perfectly at those four focal lengths(35,28,24, and 18mm)
I have some issues at about 20 - 22mm. It has slight ff.

---------- Post added 05-16-15 at 12:49 AM ----------

And it has bf issues between 0.8 to about 1.6 m distance. Subject beyond 1.8m, I do not have problem
focusing.
Dock only gives 16 total adjustments. I just wish they give us more adjustment points.

---------- Post added 05-16-15 at 01:04 AM ----------

oh, and one more thing, it seems like I get way, way better keeper rate if I set my focus at infinity first, then point something close, and viceversa.
In other words, if focus throw travels more before it locks on a subject, i get a good result.

i'll be testing more on those troublesome areas. But if I stay away from those focal length (20 - 22) at .7-1.6m focus distance, I have a confidence. I'll be shooting my friend's wedding, and I'm bringing sigma 17 50 2.8 and 18 35.
We'll see what happen tomorrow.

[sjyoon20904]

some more pictures. I don't know if I like bokeh on this one, though. I had two copies, and spent a while on AF adjustment. AF is quite slow, especially in low light condition. But I find it to be consistent. I think this lens is not for everybody, but it's worth giving a try. Interesting lens.

35mm at f1.8

[sjyoon20904]

another one from shooting around my house.
More I use this lens, more I get amazed by it. You can see ants on the bud. Amazing....

21mm, f1.8