[josephyu]

which one should i buy?

Tamron A17 70-300 f/4-5.6
Canon 75-300 f/4-5.6 IS USM
Canon 70-300 f/4-5.6 IS USM

another question.

if i found fungus in my lens, how can i
clean it?
should i take it to the shop? can it be cleaned?

please reply, thanks!

[jsklee]

where is the fungus?

[josephyu]

inside the lens.

[jsklee]

then go to cs to get it cleaned la!

[william_lau]

總之唔好買綠圈o個支70-300。

[Obi-Wan]

josephyu

The first 2 lenses are NOT as good as the cheap cheap 55-250IS

Tamron A17 70-300 f/4-5.6 (I have this one for A100, at 300mm, the photo is more very unsharp, I also the the Nikon G version of this lens, made by Tamron, also about 250mm very poor)

Canon 75-300 f/4-5.6 IS USM (old version, may be worst than the first one)

Canon 70-300 f/4-5.6 IS USM (I don't have this lens, but should be better than the 75-300 according to BobAtkins & photozone.de)

if u want a comparison, please go to
http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?SampleComp=0&FLI=0&API=0&Lens=456&Camera=452&FLIComp=0&APIComp=0&LensComp=358&CameraComp=452

[josephyu]

thanks obi-ean,
then how can i check whether a lens is good or not
when i am buying a lens from 2nd hand seller?
cause he said that there are fungus indide the lens
and i want to see whether it will affect the image.

will fungus affect image?

[william0106]

70-300的綠圈會有什麼問題的???

[jsklee]

will fungus affect image? -- depends on the size and concentration of fungus.

[h0001244]

If size of fungi is not that large, it wouldn't affect tele lens much....

[jsklee]

http://www.dcfever.com/forum/read.php?f=12&i=32213&t=32213&phorum_auth=884364bf314cb043bbbc9c025bebe286

[Obi-Wan]

josephyu

that's all depends on the price, in general fungus will "EAT" away the coating & "GLUE" between the glass elements. I will not buy a fungus invaded lens unless (1) very cheap (2) the fungus is on the front or back elements so that they can be easily cleaned

after the coating & glue has be damaged, the lens will become a "SOFT FOCUS portrait lens" producing dream like, low-contrast photos. This is usually not acceptable to many users. ^_^

for the beginners, please keep away from these lens.

BUT I did buy 2 such lenses because the price is very very cheap, one is a Nikon 28-85mm AF, still very sharp with high contrast after cleaning

[Obi-Wan]

william0106
"70-300的綠圈會有什麼問題的??? " <=== poor quality lens at the price of L lens, also the bokeh of the DO lens is extremely weird..... I bought one before & sold within one month

[josephyu]

so what about $680 for a Canon 75-300 f/4-5.6 IS USM
will you buy?
(but have fungus)

[g88]

i will only go for Canon 70-300 f/4-5.6 IS USM from ur list...if fungus inside lens mostly because repair or service.