Warning: Cheap Filters Can Harm Your Glass

There is quite a debate going on about whether one should use filters for lens protection or avoid filters for better quality.

Here is another thing to take into consideration – Some cheap filters may harm your glass, not just your image quality.

Warning: Cheap Filters Can Harm Your Glass

Roger Cicala of Lensrentals had a few Canon 24-70 f/2.8 Mk II returned with a circular scratch pattern on the front element. This can be quite annoying especially since this is a $2,000+ lens.

This got Roger to experiment with various filters. He realized that the cause for scratches is contact between a cheap “thin” filter and the slightly bulged front element of the 24-70.

The good part is that not all lenses and filters produce this undesired effect:

“It seems that you need the proper combination of a thin-line filter with glass close to the back of the filter, and a lens with a slightly bulging front element (this lens has one, but so do lots of others) to even worry about it. I would also think that wider front elements (this is 82mm) might allow more play or sag in the center making this more likely” #

Rojer suggests to “stay away from ultra-thin filters on these lenses, especially discount ultra-thin filters” or at least check that the lens does not come in contact with the filter.

[Bad Times with Bad Filters | Lensrentals.com]

  • Luciano

    Poor lens design, that what it is…

    • Marc W.

      Poor lens design? We can’t baby proof everything.

      Well, I have had a lens cap scratch the front of a lens because it was a new center pinch cap put on an old lens. I did blame myself, not someone else.

      • Vaards

        Poor lens design.

  • Siam Cat

    Surely this happens not matter what the price of the filter. Poor lens design.

    • Marc W.

      Surely you read the article linked and read the section that said “READ THIS PART”. Surely.

  • http://www.christsna.ch/ Chris

    Thanks for the tip!

  • Andrea

    … or don’t use a filter at all and use the lens with it’s hood always on for protection. Being careful with one’s gear also helps

  • Andrea

    So the Canon 24-70 f/2.8 Mk II should have a HUGE warning about screwing on it thin filters (cheap or not)…

    • Andrea

      So you must have a HUGE warning on everything? Dude, remember to breath or you will die

  • LSAGuy

    Seems to have an easy solution. Take a cheap plastic ruler, wrap it in a lens cleaning cloth and lay the edge of the wrapped ruler across the center of your lens. If it touches the center of the lens you need a deeper filter.

    • Rick

      Its not quite that simple. The filter glass is set at different levels relative to the rim by different filter manufacturers.

      So knowing where the lens glass extends to is only half the equation. You have to know where the filter glass sets relative to the rim too.