Watch out for thermals!

[Andre Regini]

Just before Christmas I was shooting a product with a wire mesh in my studio. On 100% loupe I could see that parts of it were out of focus. So I naturally checked the CCD and lens for dirt. Couldn't see anything so I took another shot. Still had out of focus areas but wierdly in different places. After 30mins of head scratching and more cleaning and check software settings, I suddenley thought that may be the two propane space heaters blowing across the studio were causing thermals. Turned those off took another shot and bingo, all 100% in focus! I'm not sure if it was purely a themal issue or droplets of water or CO2, flying across the field of view (propane gives off a lot of water and CO2 when it burns), but it really had me going.

I've now taken a closer look at these and you can see quite a lot of distortion going on in the images from shot to shot. Pretty much like you'd expect in a mirage. I've uploaded some shots of the loupe layered up in a PSD file.. www.kingbridge.co.uk/temp/mirage.zip.

You learn something new everyday! I guess that multi shot shooters see this all the time, but that was a new one on me.

100 Mega Pixel resolution? Great, but not if you've got the heating on!

Andre Regini
www.regini.com
www.kingbridge.co.uk

[Alex Maxim]

Yes, hot air mixed with cold does it all right. A jet turbine is the best example

[Jacephoto]

thanks for sharing!

[r.frank]

Thanks. its an itressting issue. I never tought about that problem 

[Andre Regini]

Got to laugh.... Was visiting a large studio here last week and saw their space heaters, so I recounted this incident to the guy running the place. Today one of his teams was shooting a car and they were scratching their heads for ages trying work out why a headlamp was drifting in and out of focus.... Yep... turned out he could point to them straight to the thermal from an Arri sitting below the headlamp! LOL!