[Hydnum]

I must pay better attention.
Bought a mint Sigma 150-500mm off the classifieds.
Thought I'd done my homework.
Turns out this version didn't offer OS for Pentax - in the real, fine, print.
No Biggie - pun not intended, maybe.
The K-5 has IS -
Love this new beast.

[Digitalis]

Probably the most expensive lens cap I have ever bought:

[Jonathan Mac]

A half litre each of Ilfosol, Ilfostop and Rapid Fixer.

[Oldhand]

Probably the most expensive lens cap I have ever bought:

Very impressive but ......
Pardon my ignorance but what is it?
OH

[Digitalis]

Pardon my ignorance but what is it?

The Sigma USB Lens dock for Pentax K mount. It is used for AF calibration.

[Oldhand]

The Sigma USB Lens dock for Pentax K mount. It is used for AF calibration.

Gratias.
Why does a lens need to have its AF re-calibrated?
Puzzled
OH

[Digitalis]

Why does a lens need to have its AF re-calibrated?

I bought the lens dock for my Sigma 18-35mm f/1.8 zoom lens because autofocus with my copy has been inaccurate and unreliable. The lens dock is intended to give end users the ability to calibrate autofocus for different zoom settings.

[Oldhand]

I bought the lens dock for my Sigma 18-35mm f/1.8 zoom lens because autofocus with my copy has been inaccurate and unreliable. The lens dock is intended to give end users the ability to calibrate autofocus for different zoom settings.

Many thanks.
I guess it will be a useful tool for those times when the lens misbehaves.
Does it fix lenses that have been dropped or accidentally mishandled resulting in inaccuracies, or is it a fix for variations in quality control.
OH

[Digitalis]

Does it fix lenses that have been dropped or accidentally mishandled resulting in inaccuracies, or is it a fix for variations in quality control.

If a lens has been dropped, it is better to have it checked by a technician in the event of internal damage affecting the lens. Quality control issues are what store return policies are for, and developing an eye for detecting them is a good skill to learn. I can spot lens defects very quickly.

[Oldhand]

If a lens has been dropped, it is better to have it checked by a technician in the event of internal damage affecting the lens. Quality control issues are what store return policies are for, and developing an eye for detecting them is a good skill to learn. I can spot lens defects very quickly.

Sorry to labour this but I can't see what other reasons there would be to fix the auto focus.
Have you found other reasons to acquire this USB dock?
Thanks again
OH

[Digitalis]

Have you found other reasons to acquire this USB dock?

It only works with sigma lenses but it can be used to update lens firmware, you can also customize other settings: you can change auto-focus speed settings*, program the focus distance limiter* and settings for optical stabilization. But beyond that: it is basically an expensive lens cap.

*this feature only works with the Sigma 120-300mm f/2.8 sport lens.

[Oldhand]

It only works with sigma lenses but it can be used to update lens firmware, you can also customize other settings: you can change auto-focus speed settings*, program the focus distance limiter* and settings for optical stabilization. But beyond that: it is basically an expensive lens cap.

*this feature only works with the Sigma 120-300mm f/2.8 sport lens.

OK, I see now.
Sounds quite useful
OH

[Stavri]

Probably the most expensive lens cap I have ever bought:

I wish I could borrow that lens cap for a day, my 18-35mm needs AF adjustment on the 20-28mm. You're probably one of the first to use the usb dock, let us know how it performs.

[dadipentak]

developing an eye for detecting them is a good skill to learn.

If you're willing to endure with the aggravation that ensues. For the sake of my inner peace, I vowed at an early age not to develop a refined taste for coffee but it happened nonetheless. My life has been hell ever since.

[Digitalis]

You're probably one of the first to use the usb dock, let us know how it performs.

I'll post an addendum to my comparative review of the Sigma 18-35mm f/1.8

I vowed at an early age not to develop a refined taste for coffee but it happened nonetheless. My life has been hell ever since.

I cringe to admit this: but I used to drink Johnnie walker - most of which is complete trash, these days I drink Abelour.

In my early days I used a Leica M3 with a pre-asph Summicron 50mm f/2 - I took the leap to much larger formats in a matter of years, with most photographers that takes many decades - some never even get there. I have been fortunate to work with some of the greatest lenses ever made - and it makes me sensitive to issues common in less-than-stellar optics. So I have to buy the best - and my bank balance suffers for it.