The shutter will operate up to 30 seconds, meaning at worst a 30 second delay for the dark frame exposure.

Does anyone know if noise reduction is active on "B" or not? I'm not sure that these sort of cameras are best suited for exposures of many hours. The sensor might get very hot and noisy in that sort of time.

Not ridiculous but actually rather clever and resulting in nice noise free images from very long exposures.

Yes, we have to wait for the dark frame subtraction, but for night shots of say fireworks it works a treat.

Classified Ads will have to be monitored more closely because they are getting very clogged up with chatter and commentary that has nothing to do with the sale.

When they go off track any non-relevant posts are likely to be removed. It's very unfair on sellers and potential buyers if there's a mass of posts from those not intending to buy.

Caveat Emptor in all cases of course, but jumping to conclusions isn't right either.

The distortion varies as we would expect, as you zoom. What is not odd is to have barrel at 10mm, but what is odd is to have pincushion at 14mm and then virtually none at 20mm. The type of distortion at each focal length is also variable, as it changes in degree along the edge....it's the price paid when designing the compromises for a very wide relatively inexpensive optic.

I should clarify what I wrote, because I was meaning 24fps, but repeating each image twice so that you only need 12 images per second.

This is how the 1930s "Popeye" cartoons were made!

If there's any distortion at all in a wide angle lens, it's much better if this is barrel distortion. Our eyes are used to that and accept it quite well.

The pincushion of the Sigma half way through the range is a bit weird, although at 20mm it seems OK again.

The figures in the tests linked to vary quite considerably from those published in the AP test, where distortion at the mid point of the Pentax lens was virtually zero. This ties in with what I have observed.

Still, the choice is there depending on how wide we want to go and any budget considerations, which might be a bit more relevant at current prices.

This probably means it has a wave of distortion that varies from barrel to pincushion along the edges. This is very tricky and a bit unsuitable for architectural subjects.

I haven't used the 60-250mm so can't comment on its speed, but I have used the 55-300mm and you need to be careful where you place the focus point to get a reliable lock with fast subjects. After a bit of practice, I can now do this OK with flying birds, but if there's a problem then MF is the answer.

With respect, this isn't the fault of the kit you use and some effort is needed to achieve consistent results with these difficult subjects. I don't think buying a second system is easier than practising for a while with what we already have.

The Pentax lens shows very low leverls of distortion, not discernable for normal use. Ideal for architecture.

The Asahi Pentax Nocta was available in the Spotmatic era, comprising twin flash guns with IR filters (no visible flash) a Spotmatic, a nightvision viewfinder and a specially corrected 300mm lens.

This was used for surveillance photography onto IR film.