I have a Canon EF 50mm 1.8. I saw a dust (1mm x 1mm) inside the lens. IS that will affect on the picture ? Which has a greater effect toward the picture, a scrath on the rear lens or the front lens. Here I am talking about a zoom lens. What is the effect of a scrath/dusty lens ? ( flare, contrast, soft image, blur, color shift ) Thank you.

-- patrick (pchar@hotmail.com), March 15, 2002

Answers

The dust will probably have no visible effect on your images, but you should try it to see if it does.

A scratch on the rear element would generally have more effect than a scratch on the front, if the scratches were the same. In any case, cratches have to be quite bad to effect the image enough to be noticed, but the usuall effects are a slight flare and/or softening of the image. Usually you can mitigate the effect completely by painting the scratch black.

-- Jim Strutz (j.strutz@gci.net), March 15, 2002.

Lenses are not vacuum-sealed, so they accumulate a little dust--which is not a big deal. To get an idea of how "bad" things can be, try taking a picture using a very dirty UV/skylight filter (fingerprints, smudges, dust & grime). You'll be hard pressed to see the effect on your print. The experiment may put your mind at ease about a few specks inside the lens.

Rear element scratches and fungus on the inside are more problematic but still have to be severe for you to notice in the prints.

-- Preston Merchant (merchant@speakeasy.org), March 15, 2002.

If your len is not bought from grey market, try to return to Canon and ask for cleaning the len.

I bought a len 28-105 for 2 weeks. I saw there are dust and 2 tiny hair (approx. 5 mm long) inside the len. I just returned the len to Canon for cleaning. The customer service said it's free of charge if the len is still in warranty period.

Now, I am waiting for the result.

-- Eddie Chan (year1997@hongkong.com), March 17, 2002.