Sigma 22.5mm filters for 600mm lens

seany65

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Sep 6, 2016
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Hello all, me bothering you again, lol.

Anyway, I've just bought some sigma 22.5mm filters which are designed to go behind the lens (Sigma 600mm I believe) but I bought them to go on the front of my Petri "Compact" half-frame camera. They fit perfectly, but while doing some research in what Sigma's "Normal" filter is supposed to do (as I was hoping it was a UV or skylight filter), it turns out that it's needed because the lens design has taken into account the use of the other filters (which I have) and without it either the image may not be quite in focus or the infinity mark may be in the wrong place or something.

My question is: will these behind-the-lens filters work just as well on my Petri as "normal" front-of-the-lens filters would, or have I wasted my money?

Thank you for any help anyone can give.
 
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