43-86mm zoom

[Erik Lund]

It's not a problem it's a feature 

[Bjørn Rørslett]

"my C is probably now a bit faster at the wide end "

Fat chance ... Even when the aperture blades are able to move further away, this doesn't entail the actual entrance pupil grows any larger. After all, its size is determined by the optical construction.

[richardHaw]

which is the one that determines the actual f-stop of the lens? the exit or entrance pupil? 

ok, balsam separation is not as bad as i thought. condensation is all gone now and glass is clear. there are some residual stuff left by the fungus or whatever that might need cleaning again but so far lens is performing normally.

i hope that alpha-Bromocinnamaldehyde will prevent any further outbreak for this lens and the others that i have now.

[Bjørn Rørslett]

The entrance pupil "collects" light on behalf of the entire optical system and hence determines the "speed" of a lens.

In technical terms, the entrance pupil is the image of the aperture opening and thus is a virtual quantity. It can actually be larger in diameter than the lens itself. Not many examples of that kind exists, but some for sure do and it is a little unnerving to look into such lenses and realise the "hole" is bigger than the lens

Further worth noting that the nominal aperture (thus "speed") of the lens always refers to infinity focus, whether or not the lens actually can reach infinity.

A well-known example is the famous Repro-Nikkor 85 mm f/1. It has an entrance pupil of 86 mm (it is actual focal length is, not coincidently, also 86 mm) and this is an f/1 lens. It is also perfectly symmetric so its pupil factor is 1 too. However, it is used at m=1 (or life-size 1:1 magnification), so its effective aperture at that magnification is f/2.  Depth of field corresponds to f/1 though.

[richardHaw]

die, fungus die! 

not sure how much this will help but at least it might help irradiate them. back in my home country, I could ask my classmates from dental school to just zap the fungus to death using the cephalometric x-ray machine that we use to radiograph the patient's mouth (i went to dental school a few decades ago, but now works in the animation industry. go figure  )

HAW_7468 by mrBabaero, on Flickr

the improvement over the older optic formula is most relevant at around f/5.6 and f/8 where the sharpness and detail can rival primes. the older one can be sharp as well but the result is just "not there". decent, but wanting

HAW_7473 by mrBabaero, on Flickr

like previously mentioned, the 1.2m minimum focus distance is kind of annoying for me when i am trying to take a picture of my baby but it's just OK for street since this i usually focus to 1.5m anyway  it's not as discrete as a small prime but it's still pretty small compared to other more modern zooms...