Well since its a rainy day here, I decided to do some simple tests comparing various macro setups of mine.
The constants:
All comparable setups (i.e. m 50mm f/1.7 vs. m 50mm F/2) have the same camera settings, same F-stop, and same flash settings. Non comparable images have adjusted settings to get a decent exposure, without affecting sharpness. In addition these are all straight out of the camera Jpegs. Combine ZM (stacking software) was used for two images. Combine zm leaves artifacts along the edges and requires cropping..... none are cropped.
The subject:
A dead jumper
The equipment used for all shots:
Metz 48 with DIY diffuser, Pentax AF 360 flash with DIY softbox/beauty dish, and my Pentax K-7.
*My conclusions are based off of me viewing each image side by side @ 1:1 on my computer. I do not know how to crop 1:1 perfectly to link here, and flickr really does make the images look like they have less IQ than they really do when comparing computer to flickr. Still.....
Ok, so now lets see some images
M 50mm F/1.7 vs. M 50mm F/2
reversed on full set of extension tubes + a hollowed out Teleconverter. 3 images stacked each (handheld..... im shocked as to how close both images are) at F/5.6 for maximum sharpness.
50mm F/1.7: 50mm F/2
original size for close up viewing (note: the artifacts like I said are from combine zm):
M 50mm F/1.7:
http://farm6.static.flickr.com/5097/5460300300_c681836205_o.jpg
M 50mm F/2:
http://farm6.static.flickr.com/5179/5460300294_6e7b40ebac_o.jpg
conclusion: the M 50mm F/1.7 @ F/5.6 is brighter than its F/2 counterpart. Both are VERY similar in sharpness. I'd give the edge to the M 50mm F/1.7, but its definitely close. Also, the F/2 50mm has noticeably more apparent fringing.
next we have the sigma 105mm macro lens. Can this $380 dedicated, built for macro behemoth, beat my reversed $30 M 50mm F/1.7?
Sigma 105mm macro
sigma 105mm macro @ 1:1 - F/5.6
original for close up viewing:
http://farm6.static.flickr.com/5097/5459786427_3a477ff240_o.jpg
conclusion: This one is up to you guys. Think what you want
Sigma 105mm macro + full set of extension tubes + hollowed out Teleconverter (for nearly exact magnification as the reversed 50mm's on extension tubes) @ F/5.6 again:
original for close up viewing:
http://farm6.static.flickr.com/5017/5459786431_ae3c1bc9c6_o.jpg
Conclusion: I think not
This is where it gets bad.... real bad. Horrible IQ IMO with the extension tubes added. The reversed 50mm's are clear winner's here.
next up:
M 28mm F/3.5 vs. F 28mm F/2.8
Reversed on a full set of extension tubes and a hollowed out teleconverter. I was not capable of stacking images for each that were similar enough to compare handheld, so these are just single images @ F/5.6.
M 28mm F/3.5:
F 28mm F/2.8:
Original size for close up viewing:
M 28mm F/3.5:
http://farm6.static.flickr.com/5098/5460358552_c19e2c67c4_o.jpg
F 28mm F/2.8:
http://farm6.static.flickr.com/5179/5460358536_58e1770920_o.jpg
conclusion: The F 28mm has more purple fringing, while the M 28mm has more cyan and red fringing. I can't decide which I think is sharper. Im going to say its a draw here @ F/5.6
next:
F 135mm + various reversed lenses
all taken with the F 135mm @ F/2.8 and the reversed lens @ F/5.6
F 135mm + reversed M 50mm F/1.7:
original:
http://farm6.static.flickr.com/5213/5459810523_37dc666697_o.jpg
conclusion: A pleasant surprise for sure! The IQ here is SUPERB.... Im buying a reversing adapter for this setup as I type
(held the lens reversed, with the help of the built in lens hood)
F 135mm + reversed M 28mm F/3.5:
original:
http://farm6.static.flickr.com/5014/5459810533_8d248509bb_o.jpg
conclusion: Holy hell! Fantastic IQ AND magnification. F 135mm, I love you
F 135mm + reversed M 28mm F/3.5 + full set of extension tubes + hollowed out TC:
original:
http://farm6.static.flickr.com/5051/5459810547_eb5cae8103_o.jpg
conclusion: All shall bow down to the almighty F 135mm!
So there you have it! I hope this was helpful, or at least informative. Any questions feel free to ask!