Sony 20 for A850

[stephen burrows]

I've just ordered a Sony 20 2.8 to go on my A850, I would like to attach a skylight filter but have read differing accounts of a vignetting problem if this is done. Does anyone have any experience of this?

Thanks

Steve

[Birma]

Hi Steve - welcome to the forum. Sadly I don't have the 20, but I'm sure someone with experience of that lens will be along soon. Please feel free to post some pictures from the 20 and 850 .

[Dr. Harout]

Steve, welcome to the forum.
May I ask why would you like to mount a UV filter? For example I quit using UV on all my lenses (I used to have them permanently on my lenses in film era).
Remember that any filter alters the light prior to entering the lens...

[stephen burrows]

Thank you. I use skylight filters for protection. I know some photographers don't like this but I've had experience of front elements being damaged in the past and have been wary ever since. I photograph demonstrations and protests quite often and there is a reasonable chance of stuff touching the front end. I also photograph in desert regions sometimes and am concerned about wind driving sand onto the lens. If I never left my studio or did very controlled landscapes I wouldn't bother but it's just a bit of protection, that's all.

[Dr. Harout]

Then you might consider a 72 -> 77 mm step up ring and a 77mm UV filter.

[stephen burrows]

Didn't think of that, thank you for the suggestion.

[Wes Gibbon]

I haven't made the calculation, but remember that the step-up ring will be about 2.5mm (guess) deep, so the 77mm filter will be further from the front element. I have a 72mm filter fitted to my 20mm and I haven't noticed any vignetting.

It is unlikely to make a huge difference, but remember a skylight has a slight warming effect, compared to a UV filter, or the new 'digital' filters which unashamedly do nothing except protect the lens and (hopefully!) cause as little degredation of the image as possible.

If you want to minimise the possibility of vignetting, you might want to go for slimline filters, particularly with a polariser which is thicker than a skylight/UV. Slimline filters cost more and don't have a filter thread at the front for further filters/lenshood (which is the main reason they are slimmer).

[Old Hydro]

I haven't made the calculation, but remember that the step-up ring will be about 2.5mm (guess) deep, so the 77mm filter will be further from the front element. I have a 72mm filter fitted to my 20mm and I haven't noticed any vignetting.

It is unlikely to make a huge difference, but remember a skylight has a slight warming effect, compared to a UV filter, or the new 'digital' filters which unashamedly do nothing except protect the lens and (hopefully!) cause as little degredation of the image as possible.

If you want to minimise the possibility of vignetting, you might want to go for slimline filters, particularly with a polariser which is thicker than a skylight/UV. Slimline filters cost more and don't have a filter thread at the front for further filters/lenshood (which is the main reason they are slimmer).

I think the sony filters fall into the slimline category. They have threads on the front. -- I've only tried one on a 24-85 zoom, but I have noticed vignetting. Also, when I went looking for slim filters, I found the cost of the Sony to be with a few dollars of the better filters form Hoya and the rest.

[Mark K]

I have put a Heliopan ultra slim filter in front of my 20/2.8. 20/2.8 is a great lens on a FF camera.

[InTheSky]

I`m usually use Hoya Pro version, they are very slim and of very good quality. Instead of that it`s B&W or Minolta original UV filter.

For the 20mm, I have never notice vignetting with the Hoya. The optical part of the 20mm is in the very center of the lens, and the 72mm diameter is very far from the optics elements. I pretty sure Minolta has done that to simplify vignetting problem. Because in fact, if it was not to support a filter, the diameter of the front lens could has been less than 62mm.

Regards,

Frank

[stephen burrows]

Thanks for all your suggestions. I looked at the possibility of using a step ring adapter but this raised the question of whether the lens hood would still fit. I finally went with the slimline Hoya which works very well with no trace of vignetting so thanks again to Frank and everybody else who took the time to help.

Steve