That might also do Pete but it's more work for the one writing the firmware and yours also requires changes when moving the aperture ring the good side is though that there would be an aperture value in the EXIF data

Sorry I explained it a bit wrong.
Don't know what a stop-down coupler so I don't talk about that.

What I mean is you've the "optical review right" where it stops down the lens.
Why can't it take a metering wide open (lens in rest position) and a metering when it preforms a "optical review" so that the camera could calculate the difference in exposure so that you can get a correctly exposed image.
This way the camera doesn't need to know which aperture is used.

I ain't talking nonsense here right?

@John, it might indeed have an epxosure error since it takes some time to make metering but it's atleast better then nothing. I don't really see though why it would metter if the metering is linear or not but maybe you misunderstood my idea.

If I understand the PZ you're talking about is the Z-pro?
I've the Z-pro and bought it as a GND kit with 3 GND of different strengths. I could get it for a very good price.
Also since it's a PRO series it use higher grade filters then the P, the Pro has hardly any colour cast.
The 100mm is more standard so the Z-Pro filter almost any square filter also it's better for ultra wide lenses.

When you press the "green button" it still closes down the aperture, I really don't understand why it can't take a reading then and when the lens is wide open (in rest) so that the camera knows the difference and calculate that.
I can't see why this can't be done.

Never heard that's a common problem with this lens, it does had some SDM problems where the SDM did not work.
If it catch focus or not has also to do with your camera and what you're focusing on.
The AF sensor needs to have contrast to judge if it's in focus or not.

Without having the camera and testing it, it's hard to say if it's normall or not for the lens (camera).

and if it was there is also the FA 77mm f/1.8, it really depends on the budget and how good the sigma 85mm is would it be come interesting.

You can recreate the coloured ones on your PC so if you won't use them to often I would not get them.

Here you can find the numbers http://en.wikipedia.org/wiki/Neutral_density_filter

Also you get what you buy, the Cokin might be cheaper but the P series give a purple colour cast.

You could also have a look at... (forgot the name)... Formatt filters I believe, the ones they make for photography go under another namesomething like, tech...

Almost, depends on what you mean with full aperture.
The crippled one will meter at the lens wide open but it can't stop down to do a metering.
, so if you've a f/2.8 lens it will meter at that but if you've the aperture ring on f/5.6 you image will be underexpose.

[quote:3496ace15f="Mike-P]
The built in IS is for the Nikon/Canon crowd I suspect .. Nikon users moan that they have nothing like the Canon 100-400mm L lens which has built in IS and if its good enough IQ wise it will take that part of the market (and Canons lens) in an instant.[/quote]Doesn't have to be, Sigma is bringing out OS lenses for the Pentax mount lately I would not be surprised some of these if not all have OS as well even for the Pentax.

I know but it's good to know if he does get it to work how to solve the problem even further. Sorry for being optimistic