You can probably get rid of the residue with a cue-tip and mild application of vinigar.
August 21, 2014, 10:07:33 AM
Topic: White residue on 1DX top dial? (Read 2148 times)
5D3, 5D2 | SY14mm f/2.8, Ʃ20mm f/1.8, 24mm f/2.8, 35mm f/2, Ʃ35mm f/1.4A, 50mm f/1.8 I, Ʃ50mm f/1.4 EX, 100mm f/2.8L Macro, 17-40L, 24-105L, 70-200 f/2.8L IS II, 1.4x II, 70-300L, 100-400L | E-mount: SY12mm f/2, Ʃ19mm & 30mm f/2.8 EX DN, 55-210 OSS | FT-QL, AE-1P, FD(n) & FL primes
It is just sweat on the dial from your finger... just clean it off with some rubbing alcohol or water and a washcloth/toothbrush and your good to go!
Canon EOS 5D Mark III w/ grip, Canon EOS 7D with grip, Canon 17-40mm, Canon 24-105mm, Canon 70-200mm F/2.8 L IS USM II, Canon 100mm Macro L IS, Canon 40mm Pancake, Canon 85mm F/1.8, 2x 600 EX-RT Flashes and St-E3-RT. Gitzo 2452L and Manfrotto 410 head.
My 1DX is exhibiting some sort of white residue buildup on the top dial, but it stays clean on the ridges where I touch it the most.
Perhaps its the same thing that happened with the T4i's:
Phenomenon The front rubber grips of some EOS REBEL T4i units produced in certain lots between May 31st through June 27th, 2012 may turn white after a short period of time. We have determined after inquiry with the rubber manufacturer and analysis, that the white substance is zinc bis (N,N’-dimethyldithiocarbamate).
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