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Old May 16th, 2004, 11:11 AM   #1
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35mm Film

35mm Film - 45~450 (tape mode) / 37.6~451mm (card mode)



Can someone translate in english what that means?

What do we "learn" from this information?
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Old May 16th, 2004, 01:19 PM   #2
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My English is not so good but I'll try.

Focus length depends of frame size. 35 mm film is de facto standard for lens compare. All photographers know that 43 mm focal length is "normal" lens with ~40 degrees angle of view (field of view). 28 mm wideangle lens, 100 mm - telephoto portrait lens with narrow field of view. It's true for 24x36 mm photo film frame. Diagonal of this frame is 43 mm or 1,7 inches.

In digital cameras and camcorders we have much smaller frame. For example 1/4,7" CCD has 3,8 mm diagonal. In this case we can see that different camcorders has the same field of view for different focal lengths. To avid this misunderstanding the equivalents focal length is used.

It means, for GS400 we have:
GS400 (zoom) - Photo35 eq SLR - Field Of View (aprox)
3,7 mm (~1x) - 50 mm - 46 grad
6,6 mm (~2x) - 90 mm - 27 grad
11 mm (~3x) - 150 mm - 16 grad
22 mm (13x) - 300 mm - 8 grad
37 mm (11x) - 500 mm - 5 grad

Finally for GS400 main information is minimal focal length 45 mm. It means we have to buy wideangle attachment for shooting in small spaces. Because minimal angle of GS400 lens is nor enough. My Panasonic GS38 has 38 mm 1x zoom, and wideangle lens not needed for me in most cases.
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Old May 16th, 2004, 01:23 PM   #3
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Thanx, Mikhail =)

I felt a bit at a loss when it came to those comparisons, but now I think I got them! =)





here's what I found before I read your answer..:

What makes a lens "normal?"

A "normal" lens produces a field of view that is similar to human vision. The diagonal of the image plane is typically used as the reference for field of view determination. A "normal" lens has a focal length that is approximately equal to the diagonal measurement of the image plane. When the focal length is equal to the diagonal measurement it produces a diagonal field of view of approximately 53 which is similar to human vision.

For 35mm film (24mm by 36mm), the diagonal measurement is 43.27mm. 50mm is close to this measurement so it is considered a "normal" lens. A 50mm lens produces a 47 diagonal field of view which is close to 53.


--------------------------------------------------------------------------------

What about digital cameras?

The CCD arrays on digital cameras are typically much smaller than the imaging area of 35mm film. This means that the focal length that produces a "normal" field of view is much smaller than 50mm.

Unlike 35mm film which is the same regardless of what camera you use, the size of the CCD array varies from camera to camera. This poses a problem. You cannot know whether a focal length is "normal", wide angle or telephoto without knowing the exact size of the CCD array. Unfortunately, even knowing the exact size of the CCD array may not help because sometimes the imaging area doesn't even cover the entire array!

Because many people are familiar with focal lengths of lenses for 35mm cameras, the digital camera manufacturers choose to describe the focal length of their cameras by reference to the focal length that would produce a similar field of view on a 35mm camera.

Consider, for example, a digital camera with a CCD array measuring 8.10mm by 6.08mm. The diagonal measurement of this CCD array would be 10.13mm. A lens with a focal length of 11.7mm would produce a diagonal field of view of 47, the same as a 50mm lens on a 35mm camera. So for this camera, an 11.7mm lens would be described as having a 35mm equivalent focal length of 50mm.

By describing the lenses this way, the digital camera companies appeal to users' familiarity with 35mm camera equipment.
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Old May 16th, 2004, 01:51 PM   #4
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from here I can see that the GS400 has a bit smaller FOV than "normal" in TELE mode, but this is not enough to shoot in a room.

how about when using the 16:9 ? should be even worse...

then the:
" When the focal length is equal to the diagonal measurement it produces a diagonal field of view of approximately 53 which is similar to human vision."

.. will not hold. right?
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Old May 16th, 2004, 02:10 PM   #5
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If the GS400 is HQ widescreen...it will increase the field of view horizontally by at least 1.33x then squeeze that into a 720 pixel line. If the GS400s FOV is 53 deg. at full pullback, it should be ~70 deg. in 16:9, if my math is correct.
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Old May 16th, 2004, 02:24 PM   #6
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Guy, doesn't the HQ widescreen mean that you have enough pixels and you don't do vertical zoom, but you basically crop part of the picture on top and bottom from TELE.

and if you have cropping on top and bottom even if you still have the same horizontal FOV you in essence lose the "normal" lens effect?
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Old May 16th, 2004, 02:34 PM   #7
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I guess it would depend on how the camera creates the image in 16:9. If there is no zoom, then the vertical stays the same and the horizontal widens by 1.33x. I believe this is how the PDX10 did 16:9, but Tommy is probably the authority since he had one.
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Old May 16th, 2004, 02:37 PM   #8
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Ah, the PDX10 cropped only slightly.

Here is the reference I was looking for.
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Old May 16th, 2004, 02:53 PM   #9
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This picture from the Sony UK homepage explains it quite well:
http://www.sonybiz.net/images/product/X/DSR-PDX10P-D.jpg
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Old May 16th, 2004, 04:23 PM   #10
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Thanks Ursula! Even better. So the PDX10 widened its FOV by 8 mm.
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Old May 16th, 2004, 04:55 PM   #11
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Its a little confusing by the pictures but the PDX10 easily extracts a 853x480 frame from its 1152x864 CCD with no vertical zoom. The photos show a little less vertical area for 16:9 compared to 4:3 but its worth noting that the PDX10 uses a much larger section than 720x480 for its 4:3.
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Old May 16th, 2004, 06:05 PM   #12
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so I guess we have to wait and see how GS400 handles the wide mode. =/

keeping fingers crossed for PDX10 solution here as well :)
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