Hi all,
In some posts I have already briefly mentioned the Cosina 100/3.5 macro lens which I have purchased in March. But the lens deserves a separate thread with more samples which I can later link to when I mention the lens. Comments and critique welcome.

Currently my photography options are restricted, both regarding budget and time. I have been infected with lens lust disease ever since I have started to follow DPR. But realistically it will take a long time until I can afford a dream lens like the new 105 VR. What to do in the meantime? I came across a link to the Nikonians' review of a budget macro, the Phoenix 100/3.5:
http://www.nikonians.org/html/resources/non-nikon_articles/phoenix/100f35-1.html
On eBay the same lens with a different label is offered regularly, the Cosina 100/3.5. (Further labels are Vivitar, Voigtländer and Pentax.) I picked up a copy for about € 80, less than 10% of the Nikkor 105 VR (suggested retail price € 919 in Germany). After the purchase I realized that there are two versions of the Cosina macro. I obtained the old, non-digital one, there is also one improved for digital cameras, probably similar to the Sigma "DG" feature. I did not notice lens disadvantages due to being non-digital though I have noticed chromatic aberrations along edges with strong contrast.

Initially I only had time to try a couple of test shots. Three children between 1 and 2 leave very little spare time and especially only rare opportunities to go for a photo tour. Finally we went for a late afternoon walk yesterday in good spring light. No time for a tripod, no free hand for a monopod, all pictures handheld within a minute or so then I had to move on. All pictures with a D70 in RAW, converted with Nikon Capture, limited final processing with Photoshop CS. I link to the "large" picture versions of Smugmug which are automatically created by the host after uploading, so it's not the optimal screen quality.

[1] The 100/3.5 is able to do "street photography":
http://trainbird.smugmug.com/photos/67206114-L.jpg
[2] ... including houses I found interesting on the way - here I liked the contrast between the decades-old entrance and the flourishing forsythia, also the reflections of the lettering in evening light.
http://trainbird.smugmug.com/photos/67206308-L.jpg
[3] The Cosina is good for nearly whole tree images, like this birch:
http://trainbird.smugmug.com/photos/67205832-L-1.jpg
(Sidenote: I was surprised how big the JPG after processing was. Usually RAW images end up with 1.5 to 2 MB when saving with Photoshop "10" quality. This one requires nearly 6 MB, an indication of the detail present in the picture.)

[4] It's also useful for trees and bushes from a medium distance like this blossoming fruit tree:
http://trainbird.smugmug.com/photos/67205902-L.jpg
[5] ... or this magnolia:
http://trainbird.smugmug.com/photos/67205926-L.jpg
[6] ... or this plum tree:
http://trainbird.smugmug.com/photos/67205676-L.jpg
[7] Of course, as a macro lens, the Cosina also doesn't have trouble with close-ups. A tulip:
http://trainbird.smugmug.com/photos/67205626-L.jpg
[8] Leaf buds of a plum tree:
http://trainbird.smugmug.com/photos/67205657-L.jpg
[9] Forsythia:
http://trainbird.smugmug.com/photos/67205700-L.jpg
Here I wasn't sure how to process the image. It has a high dynamic range. With "auto level" or "auto contrast" - which I frequently try first - highlights on the foliage were burnt. At some stage this version came up which I like although the appearance is much darker than the original.

[10] The Cosina isn't only good for nature photography, I also used it for people. Too bad that photography can't convey the smell of spring but at least I can photograph someone enjoying the smell of a flower (actually it's the tulip in [7]):
http://trainbird.smugmug.com/photos/67205312-L.jpg
[11] The ladies sitting on the kitchen staircase after the walk:
http://trainbird.smugmug.com/photos/67204730-L.jpg
[12] The focus speed of the Cosina is sub-average. It hunts frequently so I doubt it can be used for rapidly moving targets. It is able to keep up with a walking child, though:
http://trainbird.smugmug.com/photos/67204782-L.jpg
[13] And it may well be used for portraits:
http://trainbird.smugmug.com/photos/67205075-L.jpg
Is the Cosina a complete substitute for high-end macro lenses? Of course not, I expect even better results from Nikkor micros. But I am glad I have purchased the Cosina, I enjoy the flexibility of rapidly changing between normal applications of a medium tele lens and quickly moving close to subjects on the way.