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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 July 10th, 2007, 12:30 PM   #1
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Some interesting questions, not only for me I hope

OK, my questions start with first question and other mainly depend on this one:

Do I use 35mm cinema lenses or 16mm cinema lenses with SI2K?

If I use 16mm lenses does this mean that I should consider camera and the frame to be somewhat like a 16mm film lens frame? or do I make conversions? I mean if I use 50mm lens for example, will it be 50mm or is there a formula to convert?

If I use 35mm lenses what happens? because then I assume I do not see the whole picture right? because 35mm lense would project on bigger surface, and since the sensor inside the camera is 2/3 it means I will only see part of 35mm lens will project. right?

my next question is more generic. If I compare pictures which were take by:
1 - 35mm camera with 35mm lens, let's say I use 50mm lens
2 - 16mm camera with 16mm lens, and I use 50mm lens
3 - SI2K camera with 16mm lens, again 50mm lens
4 - SI2K camera with 35mm lens, 50mm lens again

how are all this picture going to be different in terms of framing and DOF? let's assume I set lenses in all cases to 1.9 iris.

and the adapater from pstechnik 2K-35 what is it going to do, I mean how is it going to change the frame in the above example.

As I plan to buy the camera tomorrow, I want to understand this aspects, so please be kind to share your knowledge with me :*)
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Old July 10th, 2007, 01:39 PM   #2
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while you're waiting for a better answer from someone else ...

The SI-2K Mini uses Super 16 lenses.

Wish I could help you with the rest of your questions! Tempted to take a shot, but someone else will be along shortly, I'm sure! Hope you like your new cam, I love mine!

Cheers.
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Old July 10th, 2007, 01:52 PM   #3
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Quote:
Do I use 35mm cinema lenses or 16mm cinema lenses with SI2K?
For best results, use Super-16mm lenses

Quote:
If I use 16mm lenses does this mean that I should consider camera and the frame to be somewhat like a 16mm film lens frame? or do I make conversions? I mean if I use 50mm lens for example, will it be 50mm or is there a formula to convert?
The sensor size for 1920x1080 is very close to 16mm, but for 2Kx1152, it is a bit larger, so you will need Super16mm lenses to prevent any vignetting across the entire range of lenses (especially wide-angle). There is a slight 1.1x multiplier on a S16mm lens, since the 2K image size is not quite 12mm across like S16mm.

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If I use 35mm lenses what happens? because then I assume I do not see the whole picture right? because 35mm lense would project on bigger surface, and since the sensor inside the camera is 2/3 it means I will only see part of 35mm lens will project. right?
Yes, you will get a FOV crop effect (multiplier).

Quote:
my next question is more generic. If I compare pictures which were take by:
1 - 35mm camera with 35mm lens, let's say I use 50mm lens
2 - 16mm camera with 16mm lens, and I use 50mm lens
3 - SI2K camera with 16mm lens, again 50mm lens
4 - SI2K camera with 35mm lens, 50mm lens again

how are all this picture going to be different in terms of framing and DOF? let's assume I set lenses in all cases to 1.9 iris.
The DOF for a 50mm lens is always the same no matter what you shoot with. The Field-of-view will change though, giving the illusion of more/less *effectieve* DOF . . . but the actual DOF of the lens didn't change.

Now for instance, in case #2 vs. #3, I'm first-off going to assume S16 lenses since I don't recommend standard 16mm. Secondly, in #2 vs. #3, with a S16 lens, you will see a slight 1.1x multiplier effect, so the SI-2K will look like a 55mm lens, not a 50mm lens.

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and the adapater from pstechnik 2K-35 what is it going to do, I mean how is it going to change the frame in the above example.
The adapter from P+S is a type of ground-glass adapter that will give you the entire FOV of the 35mm lens.

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As I plan to buy the camera tomorrow, I want to understand this aspects, so please be kind to share your knowledge with me :*)
Ask away!
Jason Rodriguez is offline   Reply With Quote
Old July 10th, 2007, 02:00 PM   #4
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Chirs nice to hear you are happy with the camera. :*)

Jason thanks for the answers, it pretty much covers all my questions, but if you do not mind can I go into more details of one aspect:

---The DOF for a 50mm lens is always the same no matter what you shoot with. The Field-of-view will change though, giving the illusion of more/less *effectieve* DOF . . . but the actual DOF of the lens didn't change.---

so, it is clear, but if we compare lenses one for 35mm camera and one for s16mm, and find the ones that have the same field of view, (by the way is there a formula for that?) so will the illusion of DOF be the same? (from your last post I understand that DOF is going to be different)
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Old July 10th, 2007, 10:23 PM   #5
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I was just saying the actual DOF is always the same . . . what you will see when comparing a 50mm lens on a 16mm and 35mm camera is a different field of view on the given subject. So the background will be just as out-of focus, but because you are zoomed in on the subject, the background on the 16mm subject will *appear* more out-of-focus that in the wide-angle shot on the 35mm subject. But in reality, the background is just as out of focus in both shots, only you have cropped on the image, creating an optical illusion.
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Old July 11th, 2007, 02:42 AM   #6
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OK, I understand that, but what I am asking now is that instead of comparing 50mm lenses on both 16mm and 35mm cameras, let's compare two different lenses, I do not know how to do the math, how to convert, what lens on 35mm camera would give you the same FOV that you have with 50mm lens on 16mm camera? so whatever the lens is, so when comparing the frames we have the same FOV, now because lens are different the actual DOF is going to be different but, what is illusion of DOF is going to be? is it going to be like the same?
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Old July 11th, 2007, 03:35 AM   #7
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Quote:
Originally Posted by Levan Bakhia View Post
OK, I understand that, but what I am asking now is that instead of comparing 50mm lenses on both 16mm and 35mm cameras, let's compare two different lenses, I do not know how to do the math, how to convert, what lens on 35mm camera would give you the same FOV that you have with 50mm lens on 16mm camera? so whatever the lens is, so when comparing the frames we have the same FOV, now because lens are different the actual DOF is going to be different but, what is illusion of DOF is going to be? is it going to be like the same?
These online calculators might help you:

http://www.panavision.co.nz/main/kba...enseqvform.asp

http://www.panavision.co.nz/main/kba...alcFOVform.asp
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Old July 11th, 2007, 07:33 AM   #8
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so whatever the lens is, so when comparing the frames we have the same FOV, now because lens are different the actual DOF is going to be different but, what is illusion of DOF is going to be? is it going to be like the same?
For a lens focal length that gives you the same FOV for each different imager, the apparent DOF should appear "similar", but it won't be the exact same. The 16mm format with a 23mm lens will probably have a slightly deeper DOF appearance than the 35mm format with the 50mm lens.

BTW Brian, great links!
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