Auto White Balance...?

I got a nice (well, as far as I can tell!) "Pentax SMC A 50mm F1:1.7" off Ebay, and it turned-up this morning so I took it for a few test-shots around the park (until it started to rain...grrr...).

Anyway, when I looked at them, some of tarmac paths looked a bit purple, but others weren't so noticeable. I scratched my head for a bit, then tried playing with the White Balance - voila, solved! But its not consistent from shot to shot, argh.

Shooting Av Mode with +1 EV, RAW, Auto White Balance, sRGB, and converting using Pentax DCU 4.

Should I be setting the White Balance by hand as well? Or am I making a different beginner's mistake...

As it was a pretty cloudy/rainy afternoon I can understand the camera could be getting confused...! Didn't have an alternative lens with me to compare, annoyingly.

Thank yourself lucky that spring is here, I got my K10D and Sigma 50-500 for xmas a few years ago, it was about four weeks before I actually got outside to use it properly

The 50mm should be very nice though.

Maybe it was Purple Rain?

It is possible that the camera has set the wrong W/B in some of the shots. Perhaps try again in different weather conditions to see if you get more consistent results then. I took some Panoramic shots with my K7 and one image was a different W/B to the rest. And once i took some Shots of a Harrier in a hangar but when a guy entered into the scene wearing black overalls the W/B changed! but it is not a common occurrence and i shoot in RAW so no big deal. Those have been the only occasions in 14,000 exposures with the K7.
Regards - Pete.

I never use AWB; mine's permanently stuck to "Daylight" unless I'm shooting under tungsten lights when I'll change it to "Tungsten". Works fine for me and it's always consistent!

If you are shooting RAW you can set the white balance when you convert it.
My K20D lives on AWB and gets tweaked when I convert. Mostly I am very happy with AWB.

I would retest your lens with the white balance set either to daylight or to a custom reading you take yourself.

Me too.

I tend to leave mine on AWB shooting JPGs, I usually take one test shot and have a quick look, if it looks ok I leave it. I only tend to change the settings if (for example) people come out orange, which generally means I need the Tungsten setting!

Same here - I am usually very impressed with AWB and a little PP sorts any mixups. It seems to struggle with sand for some reason.

Thanks all.

Not had any AWB issues before, but it was a very changeable afternoon and its a new (to me) lens!

I will stick it manual white balance for now, and put the camera (with each lens) on a metered chart at the weekend.

Thanks to the blazing sunshine that mysteriously appeared today (!), I went back and took exactly the same shots-ish : tilted the camera from about 45 degrees down to horizontal and took 3 shots like before

Fixed the colour-temperature to "Outdoor" just to be sure. And (small fanfare please) the tarmac path with the variable purpleness was the right colour today, hurrah!

Moral of the story - use fixed colour-balance when the weather is changeable and you are tipping the camera up and down - they can only guess from what they see!

Are you using the lens set to "A" on the aperture ring?

I only ask this as my Pentax-A 50mm 1:1.7 is fine AWB-wise when using the "A" setting, but when I tried setting the aperture on the lens rather than body I appeared to enter a new dimension, one where AWB is about as much use as a chocolate teapot!

Other than that, shoot RAW and the problem is easily resolved in PP.

I all depends, if you're taking pictures of air hostesses or perfume counter ladies, the orange might just be correct!

Yes I am using "A", and always shoot RAW. I was more worried I either had a duff lens or wasn't using it right!