Besides, what about the lens barrel. Doesn't changes in temperature cause changes in relative distances between lens elements, in which case the problem is not limited to just Red in this regard.
Obviously, you want to let the camera reach the temperature of the surroundings and then adjust back focus. If the temperature is changing constantly throughout the day it seems you have two choices: Control temperature of the camera, short of that, adjust back focus periodically. Focal distance change is linear: 5.6 microns per 100 degrees F. You can observe temperature changes, decide how many microns change you can live with and decide when you want to check back focus.
Hope it is helpful.
That article got it wrong. You don't have to re-calibrate with each lens change. I discussed this issue with Alfred of P+S. But you might need more than one PL mount for the IMS, with each one optimized for a range of focal lengths. This is due to the digital cinema camera's focus sensitivity. Nothing to do with analog or digital lenses - there is no such thing.
On this feature we're using Zeiss T2.1 primes, optical designs that are decades old, and there are zero problems with the RED/Zeiss T2.1 combo. In fact the footage looks gorgeous.
I personally have experienced a change in the flange focus of a RED camera due to temperature change. The camera needs to be set up at the temperatu e it will be working at. A change of 20º F will cause a detectable shift in the flange focus.
That's all for now, I've got to get some rest, this movie is not in the can yet. I will post this weekend in more detail.
Checking the back-focus is a standard procedure on ALL PL mount cameras (which before RED meant mostly film cameras). One would assume, wrongly, that all lenses are set correctly from the factory. Actually, we have checked several hundred lenses on a locked down RED with no temperature change and verified that many lenses are out, due to age, wear and tear or whatever. This is not just a camera issue. It is good to know exactly what you have, camera and lenses, prior to a significant shoot... just good practice. This is professional shooting, right?
We understand how important this practice is... which is why we made it so easy to do with our new mount. But don't think the RED mount drifts around easily. I would beg to differ on this point. I have checked my cameras many times and none have them have moved the slightest. But I still check.
Main complaint I have been hearing is that the reds FFD will change from the begining of the day after the camera is on for 4-6 hours. Seems like a slightly warm interior is where it is commonly being noticed. Hence the thought that the heat generated by the camera is causing the problem with the aluminum on the mount and possibly the camera body. If this is indeed happening then this is quite a problem. Checking FFD every 3 hours on the same set is not a good answer.
Please note these are complaints I have heard from trusted pro's. Maybe you have tested this or would be interested in trying it? I would really like to check this myself but my camera is stuck in this hold pattern thing (You wouldn't by chance have contacts or pull with a red employee or someone that could get me my camera quicker would you Jim?).
The best way is to do both a chart test and an infinity collimation test. But if you don't have one of those... the easy way is to mount your lens(es), set up a high contrast chart 6' and 10' away from the camera and light it so you are close to wide open on your lens. Loosen the screws and twist the mount until the image is sharp (should be at both distances). Lock it down. If you have two lenses that are different, you have a problem with one of your lenses that you need to know about.
If you focus by monitor (instead of tape) you will still be OK except at infinity if your back-focus is off.
Like I mentioned I did not experience this but is something I have heard from two well established pro's that I trust their judgement that own cameras. Check this thread out to read about one.
From your response Jim I can tell that you would agree that if this is found to be more then just an isolated problem that it will be a major issue. I for one hope it is isolated to just a few cameras.
Please note this is not intended as an attack or red bashing by any means. It is simply bringing up a concern with what may turn out to be an odd problem with as little as 2 cameras.
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