8-16mm HSM focal range is weird, calibrate?

Hey folks. I got a used copy of the 8-16mm HSM for my SD1M from B&H.

Something is funky with the focus…

AF claims objects 6-8" away are at 0.8m and everything else is at the infinity mark or beyond. The same situation when manual focus, most of the focal range is at or beyond the infinity marker.

I wouldn't care what the distant gauge said except that I'm also getting really inconsistent results.

Is this a lens that I can calibrate? Thoughts?

spiffariffic wrote:

Hey folks. I got a used copy of the 8-16mm HSM for my SD1M from B&H.

Something is funky with the focus…

AF claims objects 6-8" away ...

Imatest states that the closest focus distance is 24cm / 9.4 in, see:

https://www.imaging-resource.com/lenses/sigma/8-16mm-f4.5-5.6-dc-hsm/specifications/

... are at 0.8m and everything else is at the infinity mark or beyond. The same situation when manual focus, most of the focal range is at or beyond the infinity marker.

What focal length? What aperture?

I wouldn't care what the distant gauge said except that I'm also getting really inconsistent results.

Is this a lens that I can calibrate?

The lens can not be "calibrated". The SD1 can.

Thoughts?

I used to find that lens on an SD1 Merrill quite difficult to establish a precise focusing distance most of the time; especially at 8mm where everything looked in focus through the viewfinder - even with a viewfinder magnifier.

Yes, the 8-16mm lens can be calibrated / adjusted by a specialist service with an SD1 Merrill body. The adjustment of this lens is performed by the "older method", which may not be as accurate as the new Art, Conteporary and Sport lenses, but is still very good and useful because it "eliminates possible lens error" in focusing.
That's why I had this lens accurately calibrated / adjusted to the SD Merrill body. Then I will focus on the correct focusing of the lens in the range of "focal length 8 to 16mm" and the table "DoF Calculator". This is my procedure.
Peter

spiffariffic wrote:

xpatUSA wrote:

Imatest states that the closest focus distance is 24cm / 9.4 in, see:

Indeed, it didn't actually focus, I wasn't actually trying to shoot it, I was trying to see what would finally make the lens go to <0.8m. It definitely wasn't 80% of a meter, was my point.

What focal length? What aperture?

Various. I tried several combinations and little to nothing was ever in focus at all when the distance indicator was set to < 0.8m.

I have taken photos at 8mm @ f/4.5 where I had great DoF and immediately after took another shot 8mm @ f/7.1 with shallow DoF. (See attachments.)

(view full size to see that the second one is blurrier in the distance)

At 8mm f/7.1, hyperfocal distance should be 1.9 feet. That's not how it worked out!

Thanks for the examples.

The f/7.1 shot is blurred from top to bottom, not just in the distance:

7.1 vs 4.5, near:

7.1 vs 4.5, far:

I calculate** the hyperfocal distance at f/4.5 to be 786mm and at f/7.1 to be 487mm - both of which are more the published minimum focusing distance. Therefore, shooting focused at those distances should theoretically get you from "infinity" to half those distances.

Does this seem like something that calibrating the camera can fix?

Failure to focus any of the scene at f/7.1 indicates a faulty lens to me and I'm not certain that playing with the SD1 AF adjustment would somehow fix it.

Exactly how I shot quite a few shots before I realized anything was wrong.

But I was originally trusting the autofocus here.

I rarely use autofocus and never did on the 8-16, so can't help there, sorry.

Here's a street shot at 8mm and f/8 on an SD15:

Focused on the end of the street and sharpened in RawTherapee. I have another taken around the same time with the lens set to the infinity mark. It is softer, which tells you nothing because modern infinity marks are no longer accurate unlike older lenses for film cameras ....

If you got the lens cheap, you could stick to f/4.5 and focus manually ignoring the markings; otherwise send it back if possible.

** http://kronometric.org/phot/iq/DepthOfField-Lyon.pdf

This might be of interest:

http://www.trenholm.org/hmmerk/DOFR.html

spiffariffic wrote:

BTW… I think this may actually be your SD1M? I bought it off Scott!

Yep, that would be it. Small world ...

Only a professional service will find out exactly what condition the lens is in, whether it is fully functional and without defects. By accurately measuring the lens. Any other method of experimentally determining whether a lens is good or not is inaccurate and does not give correct and accurate specific conclusions about the lens error / defect..

Peter

Hi Amy, I found it best to set focus manually at the infinity mark when using my 8-16mm lens on that camera. Sometimes, if I was shooting something very close, I would set focus closer, but only if the subject was within arm's reach, or something like that. There is a lot of field curvature with that lens, so if you want to get the edges of a horizon in focus, you may need to focus just past infinity, but be careful to not go too far, because everything will go out of focus if you do.

I found calibrating a lens, especially a zoom lens, to be a lesson in frustration. I suggest you just manual focus with Sigma's ultra-wide-angle lenses, no matter what camera you use. I had a similar experience with my 12-24mm EX HSM lens on my Canon 5 D.

BTW, it took me quite a while to get comfortable with focusing my 8-16mm on that camera.

Yes, Scotty, I have the 8-16mm lens experience you wrote. When shooting, I adjust the lens manually. On very close objects just before infinity, otherwise just behind the infinity sign. Just focus a little next to it and the image is out of focus. Therefore, I always take 2-3 photos with a small shift around the infinity mark.

Peter