Barry_Green
Moderator
Been doing a few comparison shots between the various HD cameras, and it's been driving me batty that the JVC's focal length never matches the others. So I tried to quantify it:
JVC at 5.5mm = HVX at 6.3mm
JVC at 10mm = HVX at 11.1mm
JVC at 20mm = HVX at 24mm
JVC at 40mm = HVX at 51mm
(note: these are APPROXIMATE, made by setting 'em both up side by side and A/B'ing the monitor, so parallax error is at least one factor that could explain error in the measurements).
So what does this tell us? Well, if they're both 1/3" chips, then one possible interpretation is that one of their lens markings is wrong. So I used the Sony as a control, and the Sony markings pretty much match the HVX markings straight on, with the HVX being a bit more telephoto across the board, but not anywhere near the difference as exhibited by both of them as compared to the JVC (example: Sony at 54mm = Panasonic at 51mm; Sony at 4.5mm = Panasonic at 4.2mm).
And, since the HD100's lens is interchangeable and could theoretically be used on other cameras, and because there are other lenses that can be used on the JVC, it's only rational to believe that the lens markings on the JVC lens are indeed accurate.
Which leads to only one possible conclusion: the JVC's chips are smaller.
It's a rule of optics that the smaller the chip, the wider-angle the lens needs to be to deliver the same field of view. An HVX at 51mm matches the JVC at 40mm. The JVC needs a wider angle for the same field of view. Assuming all other factors are equal (meaning, focal length is accurate on both), that means the chip must be smaller.
I've long wondered if the JVC HD100 isn't just using the same chips as the older HD1 and HD10; those were 4:3 chips with 1280x1024 pixels; if they cropped them down to using the central 16x9 strip that would give them 1280x720. And 4:3 chips are typically narrower than 16:9 chips, so that would indeed go a long way towards explaining the discrepancy.
However, there's a separate piece of evidence which contradicts this: JVC has published a document that claims the 35mm equivalency ratio for the HD100 is 6.9. http://www.jvcpro.co.uk/getResource2/d2_lens_combs.pdf?id=6116 Panasonic uses a published figure of 7.7 and Sony has published a figure of 7.2. If the 6.9 is to be believed, that would imply that the chip was actually LARGER than the Sony and Panasonic -- but the observable evidence contradicts this quite roundly. So I don't know what to make of that -- perhaps JVC is measuring towards the width of the frame, and the others are measuring towards the height? 35mm film is a 1.5:1 aspect ratio, not the same shape as HD video at 1.78:1, so if they're measuring the other axis that might explain the difference.
Using an on-line angle-of-view calculator, and assuming 5.24 x 2.95 for the HVX, the numbers come out to about 4.4 x 2.5 for the JVC. Bob Diaz, care to take a stab at any of this?
When it all gets down to it, it's really only relevant if you're trying to do what I'm trying to do -- match fields of view for comparative shots. And in those cases, you just have to be aware that you don't set the focal length the same on both cams, because that will guarantee a mismatched shot. Or, this info may come in handy for knowing the comparative capabilities for determining which is the right tool for a particular task. If you're scouting a job with your FX1 but planning on shooting on an HD100, you'd want to know the differences are a lot more than the lens barrel indicates.
You'd need a .7 wide-angle converter on the JVC to match a Sony or HVX at its maximum wide angle.
On the other hand, JVC's max telephoto is proportionately more magnified than the other cameras. 88mm means even more than it does on the others; in fact, I wouldn't be surprised if the JVC at 88mm matches an XLH1's field of view at 110mm. Given that the JVC's numbers are requiring the other cams to zoom in around 30% more at the equivalent focal length, that would mean an XLH1 may need to go to 110mm to match the JVC at 88mm. Of course, that assumes that the Canon is using a 5.24 x 2.95 chip; if the Canon's chip size is different still, then that will complicate matters even further!
Hey Michael Pappas, you still have both, right? XLH1 & HD100? How about a full-telephoto and full-wide field-of-view comparison? The XLH1's wide is 5.4mm, same (basically) as HD100's 5.5mm, but Canon uses a published figure of 7.2 for 35mm equivalency. Which means I would suspect the XLH1's 5.4mm to be a LOT wider than the JVC's, and I would expect the JVC's 88mm to be about the same, field-of-view-wise, as the Canon's 110mm.
JVC at 5.5mm = HVX at 6.3mm
JVC at 10mm = HVX at 11.1mm
JVC at 20mm = HVX at 24mm
JVC at 40mm = HVX at 51mm
(note: these are APPROXIMATE, made by setting 'em both up side by side and A/B'ing the monitor, so parallax error is at least one factor that could explain error in the measurements).
So what does this tell us? Well, if they're both 1/3" chips, then one possible interpretation is that one of their lens markings is wrong. So I used the Sony as a control, and the Sony markings pretty much match the HVX markings straight on, with the HVX being a bit more telephoto across the board, but not anywhere near the difference as exhibited by both of them as compared to the JVC (example: Sony at 54mm = Panasonic at 51mm; Sony at 4.5mm = Panasonic at 4.2mm).
And, since the HD100's lens is interchangeable and could theoretically be used on other cameras, and because there are other lenses that can be used on the JVC, it's only rational to believe that the lens markings on the JVC lens are indeed accurate.
Which leads to only one possible conclusion: the JVC's chips are smaller.
It's a rule of optics that the smaller the chip, the wider-angle the lens needs to be to deliver the same field of view. An HVX at 51mm matches the JVC at 40mm. The JVC needs a wider angle for the same field of view. Assuming all other factors are equal (meaning, focal length is accurate on both), that means the chip must be smaller.
I've long wondered if the JVC HD100 isn't just using the same chips as the older HD1 and HD10; those were 4:3 chips with 1280x1024 pixels; if they cropped them down to using the central 16x9 strip that would give them 1280x720. And 4:3 chips are typically narrower than 16:9 chips, so that would indeed go a long way towards explaining the discrepancy.
However, there's a separate piece of evidence which contradicts this: JVC has published a document that claims the 35mm equivalency ratio for the HD100 is 6.9. http://www.jvcpro.co.uk/getResource2/d2_lens_combs.pdf?id=6116 Panasonic uses a published figure of 7.7 and Sony has published a figure of 7.2. If the 6.9 is to be believed, that would imply that the chip was actually LARGER than the Sony and Panasonic -- but the observable evidence contradicts this quite roundly. So I don't know what to make of that -- perhaps JVC is measuring towards the width of the frame, and the others are measuring towards the height? 35mm film is a 1.5:1 aspect ratio, not the same shape as HD video at 1.78:1, so if they're measuring the other axis that might explain the difference.
Using an on-line angle-of-view calculator, and assuming 5.24 x 2.95 for the HVX, the numbers come out to about 4.4 x 2.5 for the JVC. Bob Diaz, care to take a stab at any of this?
When it all gets down to it, it's really only relevant if you're trying to do what I'm trying to do -- match fields of view for comparative shots. And in those cases, you just have to be aware that you don't set the focal length the same on both cams, because that will guarantee a mismatched shot. Or, this info may come in handy for knowing the comparative capabilities for determining which is the right tool for a particular task. If you're scouting a job with your FX1 but planning on shooting on an HD100, you'd want to know the differences are a lot more than the lens barrel indicates.
You'd need a .7 wide-angle converter on the JVC to match a Sony or HVX at its maximum wide angle.
On the other hand, JVC's max telephoto is proportionately more magnified than the other cameras. 88mm means even more than it does on the others; in fact, I wouldn't be surprised if the JVC at 88mm matches an XLH1's field of view at 110mm. Given that the JVC's numbers are requiring the other cams to zoom in around 30% more at the equivalent focal length, that would mean an XLH1 may need to go to 110mm to match the JVC at 88mm. Of course, that assumes that the Canon is using a 5.24 x 2.95 chip; if the Canon's chip size is different still, then that will complicate matters even further!
Hey Michael Pappas, you still have both, right? XLH1 & HD100? How about a full-telephoto and full-wide field-of-view comparison? The XLH1's wide is 5.4mm, same (basically) as HD100's 5.5mm, but Canon uses a published figure of 7.2 for 35mm equivalency. Which means I would suspect the XLH1's 5.4mm to be a LOT wider than the JVC's, and I would expect the JVC's 88mm to be about the same, field-of-view-wise, as the Canon's 110mm.
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