white balance and other stuff

Had a really big shoot last week and shot over 1000 frames which threw up a few points and I'd welcome your comments. The set up was as follows: *Ist DS with 18/55, 2 Elinchrom 450 heads, white continuous background, 1/160 @f 20. White balance set to 'flash'. Nothing changed at all during the shoot but some batches of 4 or 6 frames have a very slight red cast, nothing serious and easily fixed but noticeable when viewed as thumbnails in Explorer. Why?

I shouldn't have been so smug about having a clean sensor in the past, the above set up was perfect for showing up muck. Is there any way to batch process it out in Photoshop Elements 4? In the many threads here about sensor cleaning I dont remember anyone mentioning using those 'Dust-Off' compressed air guns, anyone tried it?

I've batch processed the images to resize them to 300dpi and approx 10x8 inches but the file sizes are 5.3MB, which even on broadband will take an enormous time to upload the the labs server. Is this size right?

Thanks,

Ken

Hi Ken,

I don't know why you'd get the red cast on some images, although I would take a guess that possibly the colour of the flash would vary slightly depending on how much charge the heads held when fired...? Might be that a few shots in fairly quick succession doesn't allow the heads to gain full charge, and perhaps flash with a slightly warmer tone.

I did a shoot a few weeks back, with a white background and small aperture, using flash. Perhaps I should have posted about it, because I had the same problem as you - dirt on the sensor that was invisible at 'normal' apertures. I cloned/magic brushed them out, but as it was a small shoot, it would probably have been just as quick to re-shoot, if I hadn't already disassembled my 'studio'.

Note to self: Clean sensor before shooting with flash and white background.

Regarding the file sizes, I'm guessing you saved the jpegs at 'Maximum Quality'. Try doing a couple at 'High Quality', and see if you can tell the difference. If not, then use that setting and you'll probably get file sizes of 1-2Mb.

Dan

Hi Ken

You didn't say whether you set your DS's white balance to AWB or one of the manual WB settings (i.e flash).

As for dust/dirt on the sensor I do not believe there is any plug-in invented (yet) that will allow batch processing of affected images. I think you will need to spend a while manually removing it with the clone tool.

Regards,

Simon

I'd be reluctant to use Dust Off to clean my sensor. It uses a propellant which can end up on the sensor, and is not designed as a sensor cleaner.
Start with a dry cleaner like the Visible Dust brushes, then go on to wet if they don't get it all. If you want to try a blower then try the Rocket cleaner.


And no you can't do batch dust removal in Elements 4. Sit there with the healing brush and get rid of it photo by photo - the only way I'm afraid.

In apples aperture you can map out the dust spots on one (blanc white card shot) and apply the dust filter to those spots on an entire batch of photos.
I bet adobe lightroom can do the same.

there's a podcast on itunes called "Inside Aperture" that has excellent step by step instructions....

"Any studio shoot is not finished till you got the shot....never take ANYTHING down till you've checked your file or developed you film, in case you need to reshoot...." I hear my instructor telling my classmates that every day...

"Who raised you kids? how come nobody ever puts anything away when they're finished with it?".....Quoteth the teachers assistant...

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When using studio flash I just try a few WB settings to see which one I like. Something slightly warm usually, and more often than not AWB is just fine.

It isn't necessary to have an accurate WB, just one that gives you the required "look".

I use an air aerosol, which is quicker and easier to use than swabs and brushes. Just make sure you buy one that doesn't contain nasty oils, and always hold vertically.

As for the red cast, that sounds like a white balance problem. Not all flashes are created equal, and when using multiple lights there is always the danger of some being warmer (or colder) than others.

G

Thanks to all of you for your comments, still a bit perplexed on the colour balance problem when the set up hasn't changed at all between shots, like I said it isn't very noticeable and the lab would probably filter it out anyway.

Thanks for the re-sizing tip, Daniel, it worked a treat.

George, what do you mean by 'air aerosol'?

Ken