# Drop-in Filters for UWA



## Machaon (Jan 29, 2015)

I was recently looking at the drop-in filter solution used for the Canon super-telephotos, and it made me wonder why drop-ins aren't also used for the really bulbous ultra-wides that don't readily support front-fitting filters.

Is there a technical reason why drop-in filters aren't used for the bulbous ultra-wides?

Perhaps the optical stack of UWA lenses needs to be so close to the flange that it doesn't allow room for a drop-in filter?

Cheers.


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## neuroanatomist (Jan 29, 2015)

No room in the optical design. However, they generally have a slot for a gelatin filter at the back.


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## troppobash (Jan 29, 2015)

I live in Australia and I cannot find any info on gelatin filters
and what types or sizes are available. Can someone please 
provide info or a link? I have a Sigma 12 - 24mm EX I. 

Thanks


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## neuroanatomist (Jan 29, 2015)

troppobash said:


> I live in Australia and I cannot find any info on gelatin filters
> and what types or sizes are available. Can someone please
> provide info or a link? I have a Sigma 12 - 24mm EX I.



I'm not sure why you would need anything other than a neutral density filter for that application. Google 'neutral density wratten gelatin filter'. Kodak makes them in various densities, you would need to cut out a small square to fit.


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## Rahul (Jan 29, 2015)

The _bulbous _14mm II has a gelatin slot at the rear of the lens BUT the 17mm TSE doesn't.


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## neuroanatomist (Jan 29, 2015)

Rahul said:


> The _bulbous _14mm II has a gelatin slot at the rear of the lens BUT the 17mm TSE doesn't.



True. Possibly the large image circle of the TS-E lens precluded inclusion of a rear gel mount. Personally, for my TS-E 17L I use the Wonderpana filter holder that attaches to the bayonet mount for the lens cap.


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## Rahul (Jan 29, 2015)

neuroanatomist said:


> Rahul said:
> 
> 
> > The _bulbous _14mm II has a gelatin slot at the rear of the lens BUT the 17mm TSE doesn't.
> ...



I have the Wonderpana on order. I tried the LEE adapter - fail. Half an answer is no answer at all.


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## troppobash (Jan 29, 2015)

neuroanatomist said:


> troppobash said:
> 
> 
> > I live in Australia and I cannot find any info on gelatin filters
> ...



Thank you. I will try again any google to see where I can buy them


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## privatebydesign (Jan 29, 2015)

troppobash said:


> I live in Australia and I cannot find any info on gelatin filters
> and what types or sizes are available. Can someone please
> provide info or a link? I have a Sigma 12 - 24mm EX I.
> 
> Thanks



Get one of these http://www.bhphotovideo.com/c/product/45184-REG/Rosco_950SBCNG0103_Cinegel_Swatchbook.html or if you are worried about size, thought the rear element of the Sigma is small, get this version http://www.bhphotovideo.com/c/product/45185-REG/Rosco_950SBCNG0306_Large_3x5_Cinegel_Swatchbook.html

They both have a full range of colour correction gels, ie WB, and a set of ND grades too. They are optical quality but are fragile. I used to use them occasionally with my 16-35 f2.8 MkI. I use them for flash gels all the time.


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## neuroanatomist (Jan 29, 2015)

Rahul said:


> neuroanatomist said:
> 
> 
> > Rahul said:
> ...



It works well...but it's BIG!


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## troppobash (Jan 30, 2015)

privatebydesign said:


> troppobash said:
> 
> 
> > I live in Australia and I cannot find any info on gelatin filters
> ...



Wonderful I will look them up. 

Thank you


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## jeffa4444 (Feb 3, 2015)

Main reason to avoid rear slot-in filters especially gels is focus shift. With digital unlike film you have a single point of focus if you shift that then images will be soft. We designed a lens with rear glass filters and it has to have even a clear filter in at all times otherwise it will not be sharp.


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