Well, yes, at least in extreme circumstances. If the colour temperature of the ambient light is extreme then this can cause issues. For example, if the light is pure red, then you'll have big problems recreating blue and green (because there's no blue or green reflected back and therefore nothing sensed on the CCD).

In practice though, there's no problem. In natural light you'll not have a problem. In some artificial lights you can still get a colour cast even when WB is set...

but then with RAW you've got an infinitely better chance of getting the result you want

(I've even seen one architectural photographer use a single RAW file, and output multiple TIFF files for the WB of each lighting source - outside, inside, and other light sources - then blend them all in Photoshop. Great result!)

Matt

Chris, so it is!
And I agree - it's not very obvious!!
Matt

Actually, I can't find anything about it in the manual!
Think it must have been there in the *ist-D manual... maybe they forgot for the K10D.

But, yes, that's exactly what it is - a focus assist. And yes, it makes a terrible noise!
If you have the AF360-FGZ or AF540-FGZ they have a silent, red, AF-assist illumination
Matt

Ah! Thanks for that George... that looks exactly the same as the Sigma I saw in the Speed Graphic catalogue for £30 this morning.

(And, of course, if it's purely manual, then an old style 2-pin PC cord and hot shoe adapter will do as well. But the wireless one is much neater for portraits and still life!)
Matt

I stand corrected

Though there are (stupidly) an AF240Z and an AF240FT... any idea which has the socket??

The AF540-FGZ has a 5P sync socket - which is a very useful addition
Matt

Yup

And it's not cheap. You need a lead, and two adapters:
Sync Cord F 5P normally around £20 - £30 second hand,
Hot Shoe Adapter Fg - allows popup flash to work as well. Around £20 S/H
and finally:
Either Off Camera Adapter F (has tripod socket) or Hot Shoe Adapter F which will fit onto a hotshoe (but you have to watch out for shorting of the contacts) - both around £20.

These turn up in places like www.mxv.co.uk and www.ffordes.co.uk, as well as other second hand places.

Hope that helps!
Matt

I have a cut-down P-holder (will hold 1 polariser or 1 filter) - no real problems on the Pentax 12-24. The polariser is the only reason I keep the P system (I can't afford or justify a 105mm circ pol for the Lee kit :shock

A friend of mine has the Canon fit Sigma 10-20mm and has found that the inside circle of the P-holder has to be filed out at the corners - there's a tiny amount of vignetting in the four corners at 10mm otherwise.

Matt

Doh!

Shooting at 1/15 on a 50-135mm lens will also show up any movement in the subject as well as your hand holding. Even if SR works as it should (1/50 to 1/150s would be the general rule of thumb for hand hold without SR), then any movement will be shown as "unsharp".

As has been said, you are asking too much of the conditions and expecting your equipment to resolve the conditions.

I've done gigs too... and I get a lot of dud shots, not because of my lenses, but because of movement and handshake. Plain simple.

As I commented on your second picture, which to your mind was plain evidence of a dud lens, I have to say again that your conclusion is wrong. And I'd say that whether you were asking about a Canon, Nikon, Sigma, Tamron, or Tokina lens. I was commenting on what I saw in the image... not on the brand

EDIT: I am not discounting an issue with the lens, but your "test case conditions" are not sufficient to judge whether there's a problem in the lens. All the blurriness in what I've seen so far can easily be attributed to other causes. As George says, setup a test with the lens in controlled conditions with a tripod and see how it performs. (They were not saying to use a tripod in the concert - just to test the lens ) When you've done that, then make a judgment about the equipment.

Got it?
Matt

Looks like camera shake to me

The sharpest point is her skin (compare to her hand which is definitely OOF, and so also to the back of her head). Yet, that sharpest point is blurred. I can see there is detail in the skin though.

What was the tech specs on the image? (ie shutter speed, f-stop, and ISO)

Matt

I could always provide a good home for a neglected 50-135

Thanks for the "mini review" Ben
Matt