52mm for supertelephoto - gel

My used 300 f/2.8 IS1 came with a 52mm drop-in gel filter. My understanding is that this is standard.

I wonder whether I would gain a amount-of-light advantage by removing it for darker situations?

What does the gel filter actually do except catching some dirt that might enter the lens if it wasn't there? The optical properties of the gel are not clear to me.

Was there actually a filter in the filter holder, or do you have just the filter holder? If there's anything in there other than a UV or skylight filter, it is costing you some light and maybe a color cast. But you don't need anything in there at all.

According to Canon the gel filter is part of the optical setup of the lens and should be left in place unless replaced by one of their other "Drop in Filters".
Having said that I used to have an old (Original) Canon EF 400 F2.8 L and the Gel filter was pretty ropey certainly not helping IQ at all! I removed the (manky) filter and subtly applied a small ball hammer. Results were absolutely fine!
I do not recommend this procedure! However you could simply remove it, place some insulation tape over the hole, give it a try and see what you think - you can always put it back in if the results are not as good.

Yes, I read that you aren't supposed to just dump the filter. In that case they talk about the glass filter. In my particular case I received a used lens with just the gelatin filter in a holder.

But I have no idea of the gelatin filtering is supposed to do in the first place

I can't easily test without without leaving the lens open.

So I don't have any manuals in front of me, but I thought the "optical path" wording was all related to what used to be the stock clear GLASS filter, and NOT a gel filter.

In the MkII IS super telephotos, (and I was certain this was also true of the MkI IS units) the holders that come installed with the lens are the screw in holder, that take screw in filters and the stock one that comes with it is clear optical glass.


The Gelatin filters were options.

This is the filter that was stock for the Version II
http://www.bhphotovide​o.com …_Filter.html/pr​m/alsVwDtl

and this one was stock for version I IS lenses, (I believe they are mostly interchangeable)
http://www.bhphotovide​o.com …In_Filter_Holde​r_for.html

Going all the way back to the Pre-IS version, like the 200mm f/1.8 and 300mm f/2.8L non IS, the drop in filter was 48mm, and the stock unit on early units was the gel holder, with a piece of glass "clipped in". On later units the screw in holder with glass filter was included.


That said, according to B&H The current 200mm f/2L IS comes with the drop in gel filter only, so this has me scratching my head, as all VII IS models claim to come with the drop in screw holder.

Like Jake, I remember the "filter must be there" as referring to glass filters; gels aren't thick enough, or consistent enough in thickness or surface, to make a predictable difference to your lens' performance, so better to omit them altogether if you don't need a specific one.

I think I expressed that wrong. I realized that the original "requirement" refers to the glass filter. Which I didn't get with my lens.

I just don't get what the gelatin filter is supposed to do in the first place Sorry.

You can test by removing the gel from the filter and replacing the empty filter, or by "leaving it open" if this bothers you (dust) some gaf tape would leave no residue, and last perhaps years, definitively months.

On my 500mm, it certainly appears to work just fine with no filter in the optical path, but the af distance shifts (if I recall correctly) The ie: you still get an in focus shot, but when you remove the filter, it will re-focus to get back in focus.

I was wrong about the "stock" item that came with this generation lens. The supplied filter is always the "gel holder" drop in, BUT they are supposed to have the same clear glass filter already installed in the gel holder.

On both my 500mm and 200mm the stock "gel filter holder" has a clear glass plate installed. The Gel I think it supposed to go in with it, not instead of the glass.


Does your gel drop in holder have the glass? If not, I'd suggest getting yourself one of the clear glass filters.
If there is a gel in there you can remove it.

Mine has a Gel filter also. I just removed the gel part and just use the holder with nothing. No problem with my images. I also have a CPL and ND filter with holders also.

user manual here if it helps: http://gdlp01.c-wss.com …/01/ef400f28lis​usm-en.pdf