More on filters

Further to yesterdays experiment, I had the opportunity to have another dabble with the filters. Again on a Canon EF 17-40mm f/4.0L IS USM. My eventual aim is to make the clouds blur as they move on the wind.

This first shot is with the filter holder reversed. In this position, it can hold a single lens, I used the Z154.


Note the presence of the filter in the corners of the shot. I still have a Hoya D-Pro 1 UV filter on the lens. Next I'll try removing that (but that's for another day).

My next experiment was to try to get the longest exposure possible by adding filters.
I placed the Z154, Z153 and furthest from the lens, the Z121M. Here are the results.

I was rather shocked to see the colours in the sky. Honest, the sky wasn't purple/pink!

6.0 secs at f/22, ISO 50.

6.0 secs at f/22, ISO 50.

I've yet to figure out the best way of solving the unexpected colour cast or to find an explanation for it. For now, desaturating masks the problem.

6.0 secs at f/22, ISO 50.

Any explanations for the colour cast would be welcomed.