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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 22nd, 2009, 09:42 PM   #1
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Landscapes?

What lenses do you use for landscape videography on SI-2K?

For some reason, whatever I use is not coming out as terribly sharp, especially in the night setting. Sony EX1 looks much sharper with its stock lens, and I cannot figure out how to achieve the best sharpness on SI-2K when doing landscapes/skylines...
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Old August 23rd, 2009, 12:29 PM   #2
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Arri/Zeiss 16mm Ultra Primes, a True Pola Filter, and a good post-production.
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Old August 23rd, 2009, 12:43 PM   #3
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Any stills captured from video made that way?

It'd be very useful to look at real-world examples.
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Old August 24th, 2009, 12:04 AM   #4
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Alex.


Are you getting true infinity focus with the lens you are using? What lens are you using?

My personal preference might be to use a prime lens in the range 22mm to 25mm. This will be a bit narrow for landscapes but might also give the least issue relating to correct backfocus (collimation) if your lenses have been store-bought and not matched to the camera. Please do not take my comments as being authoritative as I am only recalling posts past and maybe not accurately.

Have you adjusted your lens mounts to compensate for the filter glass in the camera which affects the focal plane of individual lenses differently, wides most of all.

I understand the filter has the effect of shortening the distance between flange of lens and focal plane. When you get to lenses like the Kinoptik 5.7mm it has to be quite a bit closer it seems.

Any probelm with the backfocus (collimation) will become most evident at wide apertures, which your night shot lens will be set at.

The SI2K image does appear softer than the EX1 but it is also not "enhanced" in-camera with burned-in edge sharpening. Provided you have set your blacks and have no gain noise, you should be able to sharpen in post.

If you are seeking that extra bit of sharpness, apparently you can operate the camera without the antialiasing filter, but you must then add a IR filter in a mattebox or have a custom IR filter made to replace the combined IR/antialiasing filter you take out. I don't know much about this so do not hack your camera on basis of my comment. Dust on the sensor can also become a BIG issue when the filters are no longer there - a risky business.

Please heed the advice of others here over my comments.

Last edited by Bob Hart; August 24th, 2009 at 12:28 AM. Reason: error
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Old August 24th, 2009, 08:44 AM   #5
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I have only one lens that positively cannot be focused on infinity: the coveted Kern Switar 26mm f1.1 Macro RX. (On closer distances, 2-4 ft, it is very sharp closed to f2 and more. Renders fantastic face closeups. Also can "see in the dark" wide open with acceptable sharpness. But I digress...)

I don't know why, since all my other lenses can, including Nikon and Zeiss via F mount to C mount adapter. Seems like Kern needs just a tiny bit more to focus.

But, even with other lenses that do focus on infinity... the lights on the buildings seem of irregular, fuzzy shape. I do not think this can be rectified with sharpening, Bob... it really feels like the camera's resolution is not enough to resolve the image.

But how can it be, when SI-2K otherwise resolves such beautiful, sharp, 3D-like image with objects positioned a few ft to maybe 100 ft off?

I did not do any test charts or scientific measurements, but the image quality seems infinitely better for portraiture and mostly everything else with SI-2K than Sony EX1, for example.

But not landscapes!

Here's the current list of my lenses:

Computar 12.5mm f1.3 (C mount)
Kern Switar 26mm f1.1 Macro RX (C mount)
Zeiss T*1.4 Planar 50mm (F mount via adapter to C)
Nikkor 35mm f1.4 (F mount via adapter to C)
Zeiss T*2 Planar 100mm Makro (F mount via adapter to C)
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Old August 24th, 2009, 07:26 PM   #6
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The Kern lens is likely a Bolex H16RX5 lens. These were modified to compensate optically and exposurewise to about a 1/3rd light loss through the prism split for the reflex viewfinder and changes the prism brough to the lens to focal plane distance.

I cannot now remember whether the flange to focal plane "in-air" became shorter or longer.

If is longer, a simple test with your Kern lens is to set it on infinity and gentle screw the lens forward in the mount to see if that improves things. I suspect it is the other way round and you cannot screw the lens close enough to the camera to bring infinity focus into play.

In the event the distance for the Kern should be shorter, if you are using the simple "thick washer" style C-mount insert with the four screwholes that fits in front of the sensor inside the IMS mount receiver, you may be able to have a local machinist make you an almost identical "washer".

The screwhead-to-camera distance must remain the same however the thickness of the flange face to rear face can be reduced by about 0.5mm. This will move the lens physically closer to the sensor and may bring you into the ballpark of infinity focus, maybe past, maybe not enough.

If you are cheap and like risky business, you could have a machinist skim out one of the faces on your existing "washer" about 0.5mm but leave about 1/16" of material near the rim for the mount to seat down on when it is in a normal position.

With the sunken face facing rearwards, your normal lenses can be mounted. Reversed, the sunken face will allow you to mount the Kern lens furthur rearwards.

The downside to this may be that there may not be enough metal under the screwheads to allow seats for the heads to be machined into the holes on the opposing side. Or maybe the seats are already there is the mount is reversable as is. I cannot now remember and don't have the mount to look at.

There may be some literature on the web which gives you the exact flange to focal with the RX5 lenses. Subtract that from the normal 17.5mm for C-Mount and you should get the depth of the cut on the washer or the thickness of the replacement washer.

It might be worth mentioning a reveresable C-Mount option to Silvio at P+S Technik or Ari at SI. It would not hard to implement.

Last edited by Bob Hart; August 25th, 2009 at 10:57 AM. Reason: error
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Old August 26th, 2009, 01:43 PM   #7
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Quote:
Originally Posted by Alex Raskin View Post
Any stills captured from video made that way?

It'd be very useful to look at real-world examples.
Hi Alex,

Sorry but I couldn't find my original files, I export some jpg's from one 720p .mov that I had.
This clip was only a CC test from a movie I DP last year.

Hope this can be a good reference for you.
Attached Thumbnails
Landscapes?-tequila-rushes-master-00128.jpg   Landscapes?-tequila-rushes-master-00520.jpg  

Landscapes?-tequila-rushes-master-00647.jpg   Landscapes?-tequila-rushes-master-01933.jpg  

Landscapes?-tequila-rushes-master-05600.jpg  
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Old August 26th, 2009, 02:08 PM   #8
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Many thanks Andronico, Bob.

In your experience... when used with SI-2K, is there any practical difference between Illumina Super Speeds S16 vs Zeiss Super Speed MK II vs ARRI/Zeiss Ultra Primes vs Zeiss DigiPrimes?
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Old August 26th, 2009, 04:15 PM   #9
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I haven't used the Illumina Super Speeds, but I can tell you the difference between all the other lenses.
Digiprimes are lenses designed to be used with 3 2/3" CCD Cameras, so the DOF is larger, like any C-Mount designed for a 2/3" sensor.
MKII & UltraPrimes have many differences, but optically the most important is that when the MKII are a stop lower or wide open, are less consistent.
Ultra Prime look better at close ups and have a very large range of focal lengths

Regards.
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Old August 26th, 2009, 05:59 PM   #10
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I have a full set of the Illumina Super Speeds that I use with the SI-2K. Overall, for the price, I find them quite good. I haven't used any Zeiss on this camera.
Mechanically they are a bit all over the place - on some the iris ring is very tight, on others they are sloppy (& two are just right) but the images from them make me smile.

The 8mm doesn't seem to quite hit infinity but is nice & sharp on close ups - I'm not too sure if this is down to the collimation being off or the antialiasing filter/wide angle issue. This is also happening with my Kinoptik 5.7mm but this is an old lens with a fixed focus.
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Old August 27th, 2009, 12:55 AM   #11
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Rohan.


For the C-mount version of the Kinoptik 5.7mm I ended up making a custom mount which fits into the IMS mount rather than the four screwed "washer" arrangement supplied by P+S.

I cut the c-mount flange face to be 1.7mm rearwards of the IMS flange face in a dished centre before I could get true infinity focus with the Kinoptik. The Kinoptik is normally collimated so that sharp focus is on objects about 3ft away.

This could be a bit off because I did not check the actual collimation of the C-mount on back of the lens to the lens itself, so I don't know if the lens was collimated to a Bolex RX5 or a non reflex Bolex or other C-Mount type camera.

I cut the flange face on my mount slightly deeper to enable true infinity focus. The Kinoptik as you know has no focus movement. I cut the threads to a tight fit so that I can actually screw the lens forward a turn or so in the mount to bring sharp focus on closer objects.

Because the lens has a deep DOF, the rest of the image should remain in acceptable focus at the 3ft setting but I wanted that little bit extra to match the better lenses.

Overall the lens remains softer than the Cinema Products Ultra T* lenses.

A Micro-Nikkor 55mm f3.5 lens is surprisingly sharp, up there with the Ultra T* at best and focus much closer than most. The older ones have a problem with the P+S Nikon mount due to interference with the rear shoulder on the aperture ring.


Alex.

QUOTE:

"But how can it be, when SI-2K otherwise resolves such beautiful, sharp, 3D-like image with objects positioned a few ft to maybe 100 ft off?"

I don't know how the anti-aliasing filter works. It may be some sort of defocusing effect or diffuser. I think it is for dealing with colour artifacts from things like striped shirts, corrugated iron, or other fine repetitive patterns which confuse digital sensors into creating false colours. If it is a diffuser, this may have an effect on tiny sharp pinpoints of light in a high contrast background.

The EX1/EX3 is a sharper nicer picture out of the box in ideal conditions but once you have had a taste of the dynamic range of the SI2K ---- different tools for different purposes. - I don't see myself running over the mountain tops chasing kangaroos with a SI2K/recorder unit. Mini plus Macbook plus backpack might be a different story but my hillclimbing days are definitely behind me. Agile portability is what the EX family is very good for.

Last edited by Bob Hart; August 27th, 2009 at 01:17 AM. Reason: error
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