Fri Feb 08, 2013 9:37 am
It's not simply about "wiggle room". I have used quite a few professional cine lenses and heaps of good stills lenses. They all focus a tad beyond infinity!
It's needed, there are not only inevitable production tolerances, even under tightest QC, but temperature changes as well. Plus, electronic lenses carry looser tolerances than manual ones, that's inevitable not to stress the tiny motors in them. We are talking fractions of a millimeter here, and even the combination of materials used for the lens mount and the ones carrying the sensor matters when heat or cold strikes. The RED One suffered from that, but at least you could adjust it yourself. They cured it in the Epic/Scarlet with a better choice of materials, which are compensating each others temperature effects, but they still have an (even better) mechanism for adjusting flange distance.
The BMCC has no such provision, but it needs even higher precision, since we need shorter focal lengths for the smaller sensor. Flange distance is more critical the wider the lens is, that's why we see it in the Tokina at 11 but not at 16mm.
I have compared the same lenses on an Epic which was carefully adjusted for flange distance by a professional service and the BMCC, using adapted Zeiss Contax primes and the Tokina. All lenses focus a tad beyond infinity on the Epic, but the witness marks are dead on. The same Contax lenses focus just to infinity on the BMCC at room temperature, and they are not as wide (obviously) as the Tokina.
Sorry, BM, but we have a problem here. There are not many choices to replace the Tokina, which is very good for it's price on RED and very attractive if one chooses the EF version of the BMCC. I hope the MFT version will do better, I'm looking forward to use the beautiful lenses from Cosina/Voigtländer.
Now that the cat #19 is out of the bag, test it as much as you can and use the subforum.
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