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<p>Your best bet is probably an Ee-D screen, which I think has a bit more "bite" than the standard Ee-A.</p>
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<p>This is very true. I have had some success using my 5D with the FSU 1000mm mirror lens, which is a f11 design but I doubt I could have achieved sharp focus with the standard screen.</p>
<p>JDM is also correct when he talks about tripods, etc. You might also want to shoot bursts rather than singles, to give yourself the best chance of getting a usable image.</p>