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08-06-2014, 07:35 PM - 1 Like   #1
panoguy's Avatar

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Sigma 18-35mm f/1.8 "Art" and the USB Dock

After reading the "sneak peek" of the upcoming review of this new-to-Pentax-mount lens, there were a couple of comments about using Sigma's USB dock to correct the (apparently erratic?) misfocus that Adam and Alex have experienced with the lens. Maybe others have experienced this as well, I don't know.

Anyhow, here's the screenshot I couldn't include in the comments to the front-page article, showing just how skewed the focus adjustments available for this lens are:

Okay, having only four focal lengths on such a shallow-range zoom isn't a big deal, but notice that there's only one possible adjustment for anything from 3 feet to Infinity!

At least anyone with the USB dock can update the firmware for their own lens, and use the software to check when it is available...

08-06-2014, 08:21 PM   #2
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Thanks for sharing this.
I guess this is because the closer you focus the more important focus accuracy is? As in DOF increases the further away the in focus subject is. Also most of the focus motor travel occurs close focus.

I'm hoping that Sigma have determined that the biggest adjustments are needed for close focus regions.

This is interesting and great to see but I can't see this having an impact on reliability though because I get am getting the impression they are seeing random / reliability issues rather than FF / BF associated with a particular focal distance. Look forward to the review to see this elaborated on.
08-06-2014, 09:10 PM - 1 Like   #3
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Original Poster
Yep, the adjustment areas are based on the lens design (helical) and focus motor steps, so this is just what the 18-35 offers. Further, I have no idea what Adam and Alex have been seeing with mis-focusing, but I also get the feeling they're not consistent (hence, not correctable via adjustment).

The biggest advantage of the dock in this case is that it will also update the firmware of the lens, should Sigma also find a defect and address it. The app checks for updates automatically on launch (and gives you a choice whether to apply them) for itself, the USB dock firmware, and the firmware of the lens that's attached. The 18-35 has already had one firmware update (v1.01).
10-07-2014, 07:29 PM   #4
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QuoteOriginally posted by panoguy Quote
The 18-35 has already had one firmware update (v1.01).
This is only for the canon mount version of the lens.


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