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Silicon Imaging SI-2K
2/3" 1080p IT-integrated 10-bit digital cinema w/direct-to-disk recording.

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Old August 23rd, 2012, 11:50 PM   #1
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Join Date: Dec 2003
Posts: 4,356
Lens information

For interest of anyone shooting an approx Super16mm sized frame, I was moved to recheck a set of CP Ultras for backfocus after one was found to be noticeably sharp compared to the rest of the set. Using the sharpness numbers on the SI2K camera focus assist, I thought I would also see where the best sharpness for iris settings fell.

The following wordstuff is not correct lens tech terminology. As a layman I do the best I can.

The 9mm T1.35 peaks at T3. It is the sharpest lens.

The 12.5mm T1.25 peaks at about T3.8.

The 16mm T1.25 peaks at about T3.5.

The 25mm T1.25 peaks T4.

Unmodified, the 9mm lens will crop the corners of a Super16mm frame. The mod is fairly simple, dressing reliefs out the external front element retention ring, which Whitehouse AV is able to do for you. I would not recommend DIY as the positioning of the reliefs in the ring have to be exactly right. With a PL-Mount, there will now be only two of the four mounting positions available which will not vignette.

As the reliefs will now create uneven areas of compression on the front element, I recommend that this retainer is pulled down only just tight enough to stop the element from moving.

The Angenieux "Compact" zoom 17.5mm - 70mm T2.5 peaks at T4.

A Century-Kinoptik 9.8mm T2 peaks at T5.6.
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Old September 3rd, 2012, 10:21 PM   #2
Join Date: Jan 2008
Location: Mumbai, India
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Re: Lens information

Most lenses are designed to have maximum sharpness at an 'f/8 equivalent' setting to the 35mm format, or in simple terms, about 2 stops from the max aperture.

Usually, after that diffraction sets in and the images go softer.

On a side note, I'm thinking why hasn't Silicon Imaging come up with another ground breaking camera yet - the blackmagic camera is more up SI's alley.
Get the Free Comprehensive Guide to Rigging ANY Camera - one guide to rig them all - DSLRs to the Arri Alexa.
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Old September 4th, 2012, 06:28 AM   #3
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Re: Lens information

SI have been quietly updating their existing imaging application and it is as bulletproof as I have ever seen it. Switch it on and it just goes, predictably, reliably and with the comfort of a favourite jacket. The current version has an all-function status display across the top of the display in bright lettering.

As for new cameras, it is a pretty crowded environment in 35mm format digital cinema and a new chinese player is looking around the corner. If the new camera family gets up, it will give the status quo a serious shake.

Ari Presler would be the best one to inform you on the future SI offerings.

There is an exciting 3D application which overlays convergence and alignment information both in data form and with intuitive graphic display. He showed it to me live on-line via Skype from two Mini heads shooting 3D in his office.
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Old October 1st, 2012, 11:52 AM   #4
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Re: Lens information

Furthur to the above post, I mounted a couple of old and damaged Cooke Speed Panchro Series 2 lenses in PL adaptors and gave them a bit of a test outdoors with Super16mm CP Ultra T* lenses for comparison as 2K lenses. They are 35mm motion picture lenses and capable of covering a 5K frame.

The Cookes had been severely fungussed and the 75mm has deep cleaning scratches which had gone through the coating. They were given to me to fix as best I could.

Although they are flary because the damaged coatings are now gone, inside and out despite their poor condition and old tech (early 1950s) they hold up for sharpness better than I thought they would in the realworld away from focus charts. Against the light they are not too good but with the light from behind the camera, they shape up better.

I rolutinely apply about 25 points of sharpening and have done so with this clip to give some hint of what to expect closer to end product. Ignore the colours. I cannot grade to save my life and due to conflicting softwares on my editing computer the default look reproduces weird. So the colours and levels have had to be done off the raw image. My slight red-green colourblindness does not help.
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