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Old December 31st, 2003, 03:49 PM   #1
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Matte box? Mini35 exposure control...

Hey guys,

Anyone know how important the matte box is in use with the mini35? I recently had one on my XL1 (from a rental house), to test the kind of footage I could get from it. I was using a set of Zeiss superspeeds (T1.3) and did most of my shooting outdoors WITHOUT a matte box - just the bare lens. Almost all of the shots, even those where my back was to the sun, are very washed out with a light gray/white mist over the whole image.

I also shot a few scenes in low-light indoors, and they also exhibit this effect to a lesser extent. Another thing I noticed in the indoor shots was a soft, large white glow around any lights in the scene, if they were overexposed.

Now, I'm aware that a reduction in contrast is a desirable effect when using the mini35, but the "washed out-ness" of this footage seems much more than would be desired to achieve a film-like contrast.

So, could this have been caused by the fact that I didn't have the matte box attached? (it was hand held, and that adds like 10 pounds ;-) Or is this the "normal" output that requires correction in post.

I am able to get the footage to look pretty good by applying a tweeked-per-shot reverse S curve to up the contrast in the lows and highs, but I'm wondering if I shouldn't go back and ask the rental house to let me give it another go, this time with the matte box attached, to see if I can't get more clean looking footage straight from the camera.

BTW, it does seem to be exposure-dependant and I'm wondering if the setup isn't just a lot more sensitive to overexposure than the stock lens. For instance, if I stopped the relay iris down until there was no clipping, most of the washed out look went away, but then the scene appears too dark most of the time (although that's correctable in post as well.) The mist appears to "eminate" from the bright (sometimes overexposed/clipping, but not neccessarily) parts of the scene which "glow", suffusing the whole frame with the gray/white mist.

An example might be a wide shot that includes the sky (facing away from the sun), where the exposure is set to just barely overexposing the sky, keeping some foreground objects visible (not silhouetted), and keeping a bit of blue still in the sky. In this example, the sky's brightness would seem to spill glow over the whole frame, washing out the contrast. Keeping in mind that, like I mentioned, the matte box was not present, nor was any kind of filter on the lens.

I'm thinking that this may be due to my inexperience in dealing with cine lenses and how they react to different exposure conditions... perhaps this kind of thing I describe is a common occurance shooting 35 and takes careful use of the matte box and filters... well, that's what this is for, a learning experience, so any advice is very welcome (and I know I should study my ACM more :-)

paulb

p.s. I can post some grabs later if it'll help - at the moment I'm on a modem.
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Old December 31st, 2003, 05:44 PM   #2
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Grabs would help a lot. The results you describe are not typical. There is a very slight tendency for the ground glass to cause highlights to bloom, but no more so than one would expect from, say, a 1/4 Promist.

It sounds to me like there was a light leak somewhere in the optical system, perhaps something wasn't properly seated between the Mini35 and the camera.

With the sun behind you, flare should not be an issue, mattebox or not.
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Old December 31st, 2003, 08:08 PM   #3
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Thanks for the info Charles! Here are a bunch of grabs that show the washing out to varying degrees:

http://208.193.239.21/photos/m35/image1.jpg
http://208.193.239.21/photos/m35/image2.jpg
http://208.193.239.21/photos/m35/image3.jpg
http://208.193.239.21/photos/m35/image4.jpg
http://208.193.239.21/photos/m35/image5.jpg
http://208.193.239.21/photos/m35/image6.jpg
http://208.193.239.21/photos/m35/image7.jpg
http://208.193.239.21/photos/m35/image8.jpg
http://208.193.239.21/photos/m35/image9.jpg
http://208.193.239.21/photos/m35/image12.jpg
http://208.193.239.21/photos/m35/image13.jpg
http://208.193.239.21/photos/m35/image14.jpg
http://208.193.239.21/photos/m35/image15.jpg
http://208.193.239.21/photos/m35/image16.jpg
http://208.193.239.21/photos/m35/image17.jpg
http://208.193.239.21/photos/m35/image18.jpg
http://208.193.239.21/photos/m35/image19.jpg
http://208.193.239.21/photos/m35/image20.jpg
http://208.193.239.21/photos/m35/image21.jpg
http://208.193.239.21/photos/m35/image24.jpg
http://208.193.239.21/photos/m35/image25.jpg
http://208.193.239.21/photos/m35/image26.jpg

Here are two shots taken at different gain levels, intended to test exposure differences (iris was full open as the sun was going down.) Note that both shots looked washed out (one being washed out to dark, the other to light.):

http://208.193.239.21/photos/m35/image10.jpg
http://208.193.239.21/photos/m35/image11.jpg

Here are some grabs from a few test shots at night, that were inteded to test the ultra low light high gain aspects. Note the black isn't really black.

http://208.193.239.21/photos/m35/image22.jpg
http://208.193.239.21/photos/m35/image23.jpg

And finally here are some grabs from the stock lens, taken in the same environment (the different size of the black bars on the sides here are only because I had the aspect bit set differently when I made these snapshots in vegas):

http://208.193.239.21/photos/m35/stockimage27.jpg
http://208.193.239.21/photos/m35/stockimage28.jpg
http://208.193.239.21/photos/m35/stockimage29.jpg
http://208.193.239.21/photos/m35/stockimage30.jpg

Any thoughts/advice are much appreciated!

paulb
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Old January 1st, 2004, 02:49 PM   #4
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Paul,

To answer your first question directly, a mattebox is a "luxury" that is certainly not required. In the modern world it serves two purposes. One is to block, or matte, light so that flags and not needed external to the camera to protect the lens. In this situation, there is no appreciable change in image quality, unless of course you had a lot of flares. The second is to hold filters.

If you are not using filters, and are not unhappy with the current state of your flares, then don't weight yourself down with one.

As far as your images specifically, at inital glance I would currently agree with Charles that it was the particular optics of the Mini35 rented i.e. in my opinion, they need to be cleaned. It would help to know where you rented it from. I have passed along this thread to a couple of people within the Mini35 tech chain and will report back if there are any other thoughts on the subject.

mizell
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Old January 1st, 2004, 03:53 PM   #5
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Paul,

The images bear out my initial guess which Mizell has correlated. Sorry you experienced this problem, that's frustrating. The rental house should be made aware of this issue.
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Old January 1st, 2004, 04:41 PM   #6
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Hey guys, thanks a lot for the followup.

Definitely frustrating since it represents about 8 hours of shooting... luckily this particular shoot was intended to be a learning experience for me, as DP, for use in an upcomming jazz music video, so the poor footage isn't a huge loss in this case since I wasn't burning any talent's time. However, I was planning on showing this footage to the director and band with hopes to convince them to go with this equipment but I can't really use the footage I have so far to do so.

I rented the mini35 from MPS Studios in Dallas (www.mpsfilm.com.) Mark Beasley was the fellow in charge of this equipment. MPS Studios seems like a great place, and Mark was very helpful.

I'm going to forward this thread on to him to see if we can figure out what went wrong, correct it, and hopefully MPS will let me give it another go at getting some "proper min35" footage. I first wanted to ask the forum here to see if my results were atypical, which it sounds like they were. Mizell, I will cc you on this email to Mark in case you might be able to help diagnose the problem.

Thanks guys!
paulb
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