Just how critical is fungus, or dust particles for that matter, on a lens surface?
I just picked up a Vivitar 400/f 5.6 P/K (Komine) for under $50. It was accurately advertised with haze and fungus so no surprise there.
I took the time to shoot a few "before" pictures (for a change) before I opened the lens for inspection and cleaning but I didn't take the time to look at the images. These old, long teles are pretty simple so in less than an hour I was ready to shoot some "after" shots for comparison.
That lens has three large (70+ mm) front elements in three groups. The front lens had/has a light, bluish haze and as is typical, cleaning didn't do much to improve that. The back-side of the third element was evenly covered with lacey fungus to about 15-percent of the total surface. Not TOO ugly looking, but certainly the sort of thing that turns off buyers. That cleaned up nicely with just alcohol and lens fluid.
I'll let you decide for yourself just how critical fungus was, at least in this particular case, based on these images of a super sophisticated test target. In my experience, this is a typical outcome.
K100DS @ ISO 400, Best JPG from a steady rest at a distance of 210 feet. All pictures are at F11 since that's how I shot the best "before" image. Cropped, equalized exposure and added the same very small amount of sharpening after resizing. Focus point on shiny bar behind seat. In order of upload:
1. The "before" shot. Surprisingly, just not much degradation due to lens condition IMO.
2. The "after" shot. If I don't compare 'em side-by-side I loose track of which is which. Compared to the original JPG files, there is a very slight increase in contrast and apparent sharpness in the "after" shots.
3. While I was about it, I added two TC's to the mix. This is a Tamron 1.4 AF. Check the speedometer and strands in the rope.
4. This is with a Tokina EL 2x Auto TC.
I'll refine these later. Harsh lighting won't be quite so kind and CA and fringing are present at F8 and F5.6 but just barely noticeable in this light. Nowhere near as bad as the Tamron 70-300. Obviously, this isn't an FA- or DA* lens but for < $50 it demonstrates what some of us have known all along, ugly lenses ain't all THAT bad - and the girls really do get prettier at closing time, too!
Incidentally, as I just recently learned , there's two (if not three) major variations in the Vivitar 400mm lenses. The current PF Lens Review is incomplete. This is the dedicated P/K mount by Komine. I'll put up some direct comparisons with the Tokina TX-version later.
H2
It just occurred to me that I see more difference/improvement in the OOF background of the "after" image than in the in-focus areas after cleaning out the fungus.
Last edited by pacerr; 05-06-2009 at 07:19 PM.
Reason: Added thought