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18mm Sigma f2.8 m42 Filtermatic Lens
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PostPosted: Tue Aug 11, 2015 7:04 am    Post subject: 18mm Sigma f2.8 m42 Filtermatic Lens Reply with quote
Can find little info on this. Can the filters be removed . One of them is clear but does it degrade the image. Just how good or bad is the image. All thoughts gratefully reviewed.


PostPosted: Tue Aug 11, 2015 10:36 am    Post subject: Reply with quote
Are you sure the internal filter, as a part of the lens design, will degrade the image? I have heard the image will degrade if you remove it.


PostPosted: Tue Aug 11, 2015 4:57 pm    Post subject: Reply with quote
To be honest i can find little info. Not if the lens is worth buying for its IQ and nothing of filters.


PostPosted: Tue Aug 11, 2015 5:09 pm    Post subject: Reply with quote
Sigma Filtermatic 16mm f/2.8 Fisheye. http://photo.net/classic-cameras-forum/00aKEL


PostPosted: Tue Aug 11, 2015 11:24 pm    Post subject: Reply with quote
mark fewtrell wrote:
Sigma Filtermatic 16mm f/2.8 Fisheye. http://photo.net/classic-cameras-forum/00aKEL


That's a very helpful reference. Thanks.

I can only offer an opinion. I don't know for certain. But I think it would be OK to use this lens without a filter. The clear filter referenced is most likely just a UV filter, useful in some circumstances but not really mandatory in many others.


PostPosted: Wed Aug 12, 2015 5:50 am    Post subject: Reply with quote
On the 16mm lens, the filters are monted at the back of the lens (the optical block is mounted on an internal bayonet and can be taken apart) and they are part of the optical path, as you can see on this picture (not mine):

SIGMA-FISHEYE 1:2,8 f=16mm FILTERMATIC by Christian Dandyk, on Flickr

If you use the lens without any filter mounted, you may not be able to reach infinity focus.

But this is on the 16/2.8 fisheye. Your first post was about the 18mm Filtermatic, which is a different lens (rectilinear superwide akin to the Tamron 17/3.5). If your lens is really the 18mm, then the filters are built-in on a rotating turret and cannot be easily removed. There are 4 filters (LB 180 / light blue, O-56 / orange, Y-48 / yellow and L-1A / UV - Clear) that can be selected by rotating the foremost ring on the lens:


Credit: Allphotolenses.com

If the filters need to be cleaned, then your best bet is to carefully disassemble the lens to be able to access the filters (or to have it done professionally if you think it's worth the cost).

Cheers!

Abbazz


PostPosted: Thu Aug 13, 2015 1:33 pm    Post subject: Reply with quote
You are right about posting 16mm. With little to go on i rather assumed they would have the same design. It does say these are "filters" though and not part of the optical focus. However i need more info about performance and the like. In its day this was an expensive lens.


PostPosted: Thu Aug 13, 2015 6:56 pm    Post subject: Reply with quote
I had the 16 for a while and didn't like it at all. The 16 isn't rectilinear, which was the main reason I disliked it. But I also didn't like it as lens, hard to pin a real reason ..... I just didn't like it.
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