Scratched lens

Stormchase · Nov 14, 2009

Ok, I have a EF 75-300 canon lens. Just the other night I was cleaning it and noticed a good size chip in it. If you can picture a BB at 1/4 moon. Just a sliver but deep and also a handfull of speckles. I talked to a shop and they said it would be about $150 dollars to ship it to canon to have it fixed. The lens was about $150. Is there a cheap way to fix chips?
Also I have not really gotten the chance to see for soft spots.
Suggestions?

Overread · Nov 14, 2009

Well as the lens will cost as much to repaire as new its not much point in having it fixed up if you can just go get a new one. However take some shots and see if the chip appears in them - might be that its outside of thefield of view for a crop sensor camera anyway (remembering that the edge of the image is not captured by a crop sensor camera when using fullframe compatable glass).
Unless it starts to show up (small aperture shots would show this more - so a few f13, f16 shots of something bland like a greyed over sky) I would not overly worry about it

Stosh · Nov 14, 2009

On a telephoto, a chipped front element will not show up as a "spot" in that location on the image. And a crop sensor does not only use the central part of the front element, it needs the whole thing, so it's definitely going to have an effect. But if the chip is near the outside edge, stopping down will help to not use light from that area on the front element. But if it's like almost all chips, it's probably near the center.

The chip will create a general softness to a low contrast image. A high contrast image will better show whatever flaws there might be. Shoot scenes with point sources of light and then other high contrast scenes and see if you can deal with the results.

After shooting several different scenes, one thing you can try is to put a black circle over the chip - only as big as it has to be. It doesn't have to be black, but black's better because it doesn't reflect as much light. This could be as simple as taking a hole puncher and making a circle from the adhesive end of a sticky pad. The idea is that the circle will interfere less than the nasty diffraction that chip is going to make because of all the odd angles and edges.

Try re-shooting the high contrast scenes and see if there's a difference with your new circle lens mask. If it makes an appreciable difference, go permanent with black paint. Use a hole in paper as a stencil to get as close to perfect circle as you can. As you already know, you might as well buy a new one instead of fixing this one, so you have nothing to lose.

Good luck.