SAVH Loc: La Jolla, CA

I have been impressed with the Sigma Art lenses. However, it appears one has to buy a separate USB dock in order to "calibrate the lens to your computer!" Looking at the offerings on Amazon and elsewhere along with the various questions and answers, I still can't figure out what it does and if it is necessary. How is the Sigma Art lens different from a Nikon, Tamron or other lens for which I don't have a USB dock? I do understand that there is a capability to calibrate a given lens with a special chart to somehow correct a difference in focusing of a standard or correct lens to the one you might have but unless Sigma lenses require a higher percentage of "corrections" to operate correctly, I'm not sure what is actually going on. My son uses his Sigma Art lenses without a USB dock and they seem to work quite well. I would appreciate a reasoned explanation. Thank you in advance.

Scotty

Bill_de Loc: US

Nikon allows one saved setting per lens. Although I haven't used mine yet, I read it can save multiple settings for various distances and focal lengths (zoom lens) for each lens.

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SAVH Loc: La Jolla, CA

Thank you, Bill.

Scotty

speters Loc: Grangeville/Idaho

speters Loc: Grangeville/Idaho

You do not calibrate it to your computer, you adjust it, so it works more efficient with your camera!

SAVH Loc: La Jolla, CA

Thank you. Do you know how it makes it work better or how the USB Dock adjusts the lens? How much of an adjustment do you see?

Scotty

brucewells Loc: Central Kentucky

I have three of these lenses and they all focus fine. So, I didn't get the dock to calibrate the lenses, but rather, have the ability to upgrade the firmware of the lens should it ever be necessary. About every 6 months, I run the supplied application, connect the dock to the lenses and it checks to see if there are updates. There have been none so far.

The dock is simply an accessory.

mwsilvers Loc: Central New Jersey

Depending on the lens/camera interaction, usually as a result of different manufacturing tolerances, the need for calibrating a particular copy of a lens to a particular copy of a camera can vary from unnecessary to extremely noticeable and necessary.

Lack of pin sharpness can also become more noticeable when you crop images. The USB dock corrects front and back focusing issues at various focal lengths and at various distances. For prime lenses there are four separate adjustments that can be made, and for zoom lenses 16 adjustments. Whether or not you may want to take the effort to calibrate your lens to your camera body is dependent on your personal expectations for sharpness at different focal lengths and distances to your subject.

The calibration process using the USB dock can be difficult and very time-consuming, especially for the novice. Tamron now has a similar system for their lenses. The results, when calibrated properly, can be significant but many people either do not see a difference, or do not want to take the often huge amount of time and effort needed to calibrate a lens properly to get the very best from it.

SAVH Loc: La Jolla, CA

Bruce, Thank you. That was very helpful.

Scotty

SAVH Loc: La Jolla, CA

mwsilvers, Thank you as well. Your answer pretty well fleshed out the explanation I was looking for.

Scotty