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Forum: Pentax SLR Lens Discussion
02-26-2016, 12:53 PM
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If you do find a way to clean inside your front element please share, even though I will never follow that path:). Good luck in this endeavor.
I know you weren't planning on using it on tubes, but I thought I'd give it a go just to see what happens. You can get pretty darn close to 1:1 magnification with extension tubes at the fisheye at 17mm. The attached is with ~18mm worth of tube (lower measurements are cm). Any longer tubes and I think the focus end up in the lens somewhere:hmm:.
The quality here is rubbish, my cheap tubes have no coupler and we're looking at f/32.
At this point you are pretty much touching the front element to get your object in focus. I had thought the working distance was about as awkward as it could get at the minimum focus distance without tubes. I was wrong:D
That dust you were worried about will probably start to show up. There are a few dust particles visible in this sample and that nasty looking black scratch near the top of the ruler (near the 4 and 3/8" mark). I believe this is from a very, very faint scratch on the front element of my lens that I can only see under absolutely the right conditions. You won't be able to tell the dust on the lens from dust on my sensor or dust on the ruler, but I was able to rotate the lens (the sections in my cheap tubes are the screw type) and some of the dust as well as that black mark definitely rotate with the lens. I will point out that at 17mm, f/32, minimum focusing distance, no tubes, none of these marks are visible in a photo as far as I can tell.
I've found this fish to be great fun for closeups, I haven't done much with live targets with it yet, but numerous fungus. The perspective difference and field of view can be refreshing compared to a longer focal length macro. Enjoy it, and try not to let the dust bother you (I'm partly saying this to reassure myself:)).
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