Heat related backfocus issues?
 

Just finished a shoot in Charlotte this weekend where temps hovered around 90F. All of the footage looked fine except one interview shot during the heat of the day. I had been in full sun and began shooting this interview when I stopped and checked my focus. I could get a sharp focus on his eyes, and would pull out and recompose but the image would go soft. The backfoucus ring had not be bumped or moved accidentally. After the interview I shot b-roll of this man inside the house he was building where the camera had a chance to cool down. From that point on my footage looks fine again. I have heard of other cameras like F900s displaying back focus issues in high temperatures. Does this seem plausible?

Could it be that the iris was stopped down so far you were getting softening due to diffraction?

Certainly extreme heat can affect back focus as the materials in the lens expand at different rates, but I have shot in hotter (120f) and colder (-34f) climes than that and not had any problems.

I can vouch for Alister's coments, I too had a problem when stopping the lens right down. In the past I have avoided using the ND filters due to a shift in colour (another make of video camera) but the Sony EX3 does a good job with ND colour, so now I use it all the time and lower my gain to -3

After going back to my footage I was indeed doing interiors right before his interview. I can only surmise I must have rolled out the ND inside and then, in the rush, forgotten to roll it back when I got outside. D' oh! I normally run my iris at a 2.8 - 4 with pleasing results. Gentlemen, I tip my American hat to you. Thanks for the lesson in diffraction.

Dave

Softness due to Diffraction on f8 or higher f stops is the dirty secret of the EX and really is quite a problem.

I thought it was no big deal until I got into a fast moving situation this week where I had to adjust quickly between shade and sun.

Because I couldn't use my higher f stops my range of quick and easy iris adjustments was limited. I had to keep switching filter wheels and this screwed up the continuity of smooth shooting.

Lenny Levy

I agree completely. Smooth, continuous shooting in changing environment (lighting, color temp) is indeed difficult, if not impossible, with the EX1. I realized that soon after I switched from my old V1E - with the latter, I could shoot uninterrupted long takes while running & gunning. ATW worked perfectly, and the ND switch was quick and precise. In those situations, all I had to take care of was focus (with iris on auto).

With the EX1, ATW is unusable and ND switch tends to stick in-between positions (and is very noisy, which can spoil the audio if being recorded simultaneously with the on-camera mic). Of course I try to avoid anything auto, and prepare each shot carefully before actually taking it - but inability to produce smooth results in run&gun situations is definitely a serious shortcoming, especially considering the camera's form factor, assuming mobility!

I realize this might sound "amateurish", but when I really need a long uninterrupted take in drastically changing light, I engage ND1 (the "middle" value), and put the shutter on Auto - in TLCS, I limit the iris closing limit to F5.6 to avoid diffraction softening (or control the aperture manually). This is the only way to achieve the goal without the constant need to change ND filtering during the shots...

Softness due to diffraction above F5.6/8 is a problem with many HD cameras especially ones with inexpensive lenses. Just another thing to think about when shooting. Best to due a test to see when your camera starts having the problem so you know how close to the line you are when shooting

I agree completely - I still have my V1U and the ATW is far superior as well as automatic focus - so much so that I used autofocus 99% of the time(on the V1U) and when my PMW-EX1 had to go in for service I started using the V1U on manual (like I was doing with the EX1) and found it had a horrible backfocus problem which I had never recognized before (in looking up on the forum a lot of the early V1U's had the problem).

For my particular use of the PMW-EX1 (family videos with three young children) using the PMW-EX1 for "run and gun" type shooting I have found to be quite cumbersome - what with constantly changing lighting conditions and constantly changing "targets" it certainly would be nice to have adequate automatic settings for those situations - of course, when the PMW-EX1 is set properly there is no comparison in the picture quality between the two camerars.

If Sony has the capability to put superior autofocus and ATW in the V1U - I wonder why they didn't do that for the PMW-EX1 - would the cost have been that much different? Especially with autofocus - don't see how some of these guys are able to handle "run and gun" - when I have tried that the focus is constantly going in and out - manual focus becomes an absolute necessity - not so with the V1U.