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Canon 17-40mm reflections in dome port
By Stephen Frink

Dear Steve - Every time I shoot into the sun with my 17-40mm lens on my Canon EOS1DsMKII with my Seacam housing and Superdome, I get a series of reflections. At first it was the white letters on the front of my lens that would show up, so I used a Sharpie to black them out. I may be a proud Canon shooter, but I got a little tired of seeing "Canon EF Lens 17-40mm" lightly imprinted on all my shots towards the sun! But I still get concentric circles from the little ridges on the front of my lens. What can I do!!!??? Jamie

Dear Jamie - I know exactly what you mean, and it is not just the Canon 17-40mm but also the 16-35mm zoom. The paint on the front of the lens is too shiny, and shows up detail reflected against the inside of the dome in some light conditions. I’ve gone through the same protocol you have in terms of blacking out the white letters on the front of the lens, and I have also used electrician’s tape to cover the red trim ring found on Canon L series lenses. But, that reflection from the concentric ridges on the front of the lens has been particularly vexing, and many an hour has been spent with the Photoshop healing brush to get rid of it. This shot is typical of the issue, but with darker backgrounds the effect is even more extreme:

I tried various kinds of dulling paint, with no particular improvement, and then I thought a lens shade might do the trick. Not the Canon lens shade though, because it is much too wide to fit through the port orifice, so I got a 77mm collapsible sunshade made by B+W filters. (I got mine from B&H Photo for around $50 as I recall). The collapsible part is very important, no matter what brand you get. It has to be soft enough to bend and coax though the port, and then pop back into shape once inside the dome. Other brands may work as well, but I have positive experience with this one.

All seemed like it would work fine, but then I discovered that the corners would vignette on my EOS1DsMKII using this particular sunshade. Of course the 1DsMKII is a full frame sensor, so this would not be an issue with an EOS1DMKII (1.3 chip) or a 20D (1.6 chip). But one dive with the standard lens hood revealed corners like this:

And this was a F-5.6. With a smaller aperture the vignette effect would be greater, and naturally the dark corners would intrude a bit more with the wider 16-35mm lens. Not a drastic distraction in the photo, and of course I could have fixed this in Photoshop too. But I figured 5 minutes with a scissors would be better than cumulative hours in front of the computer later. To eliminate the problem, I just trimmed the sunshade with a scissors, creating 4 small scallops at the corners.

Not too fancy, but it really does works, even pointing into the sun.

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