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Full spectrum external filter options...
Hello all,
Following the full spectrum modification to my Sony A7s, I need 2 external screw on filters (to the lens thread) to cut IR and UV for daytime and widefield astro images. Ive been looking at the IDAS filter options, and one of there filter choices is good for me, specifically the astro filter, and the other I was needing for daytime (but can be used for astronomy aswell) goes up to 52mm thread size and my lens threads are 67mm, a step down ring would see me loosing aperture on one of my lenses... possibly, see below.
What have others used who have had full spectrum mods done, to cut out unwanted wavelengths for daytime use?
I have been looking at the IDAS HEUIB-ll 52mm filter, this can be used for astro and daylight photography, my concern is it's diameter. for example, I want to use it on my 70-300 f4-5.6L lense, at 300mm it's aperture is 53.6mm, so no great loss of light there when using a 52mm filter. But the glass on the front is larger than that and it's filter thread size is 67mm. So if I use a step down ring (67 - 52mm) would there be an issue in terms of image quality with using this smaller diameter filter on the front of the lens?
I want to also use the same filter on my Sigma 35 f1.4 lens. It too has a 67mm filter thread on the front, with the glass being larger than 52mm, but it has a max aperture of 25mm, so this should not be a problem... correct??
Thankyou for any help!
Josh
Last edited by Joshua Bunn; 10-03-2016 at 06:41 AM.
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