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Why are camcorder imagers so small?
I suspect I know the answer to this question, but I just wanted to ask all you engineer types out there, and throw out a bit of speculation on where camcorder imagers might be headed.
It seems that the current crop of high-end small camcorders (e.g. XL-2, Z-1, HVX-200) all have rather small imagers, especially considering they are all being marketed to independent filmmakers. One of the biggest limitations of these camcorders is the simple physics inherent in having a small imaging surface, and therefore, an increased depth of field. My question is why aren't video cameras geared towards professional use equipped with 35mm size sensors? It would seem that this one, simple design change would go a long way towards enabling more filmic imagery. I wonder if it is somehow cost-prohibitive to produce such large sensors, if the legacy of video cameras for ENG photographers has dictated smaller imagers to PRODUCE more depth of field, or if the desire to produce smaller, lighter camcorders trumps the use of larger image sensors. My suspicion is that the latter is the case, but only for 3-CCD designs, and only for small camcorders. If you needed to design a 3-CCD prism block, and each sensor had to be 35mm, or larger if you include the surrounding electronics, the block would end up being huge. Maybe much too big for such small cameras. If, however, you were to use a single sensor, such as the CMOS in the new Sony HDV camera, it should be a trivial matter to make the imager much larger. It might even be easier, as it's always a challange to miniaturize electronics. Am I completely off base with this assumption? There are plenty of very small 35mm film cameras, and even many digital SLR's with very large imagers, that still manage to keep a smallish form factor. Just because the imager is 35mm, that doesn't mean the camera body has to be huge, or that the lens needs to be any bigger. If both the Dalsa and the Genesis cameras can use a true 35mm-size sensor, how long before that kind of technology trickles down to the sub-$10,000 or sub-$5,000 camcorders? Or am I missing the picture entirely - that the manufacturers are perfectly capable of doing it, but don't because of some marketing reason. I'm just curious, as it always seemed counter-intuitave to me. When a shallower depth of field produces such pretty images, and filmmakers are forced into clunky and expensive optical workarounds, why are manufacturers often opting to go in the opposite direction? |
the cost of the sensor is nothing regarding the cost of the lens.
for small sensor, you can build plastic lens for very cheap or pseudo "zeiss" quality if you need some high end result (for HDV for example) just look at the price of 1/2 inch lenses and you will understand. |
Giroud makes an excellent point. Take a look at the cost of broadcast lenses that are designed to target the larger ccd's. And that's not even 35mm format. Look at the cost of 35mm prime lenses. Look at the SIZE of a zoom lens for 35mm cams.
The sensor is a small part of what it takes to get 'that look'. Even the work-arounds with spinning gg and primes ain't cheap. |
The big factor in CCD and CMOS sensor costs is yield: how many *good* arrays you can get out of a wafer of silicon. The larger the array, the lower the yield, and it increases with the area of the array. If the yields were the same, a 1/2" CCD would still cost almost twice what a 1/3" costs (to manufacture). But the yields are a function of area too, so you not only get less *good* units per wafer because of size, you get even less because of the area. So a 1/2" array probably costs more like 4 times what a 1/3" costs (manufacturing cost). A 35mm-sized array is then going to cost about 400 times what a 1/3" CCD costs. As manufacturing methods improve, yields go up, costs go down, but there's still a huge difference.
Lenses are also a factor, but Fujinon and Canon could make and sell 1/2" and 2/3" lenses at prices close to what the 1/3" Canons now go for, if the volume justified it. |
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Sensors are made in waffles: the more you can fit on one waffle , the better the chances to get a few good out of it. The bigger the sensor, the smaller the chances to get ALL pixels good on one chip, hence the higher price. Lenses add up. Storage of data. Size, weight, convenience in use and............................. His Majesty THE PRICE (son of a B-udget) The lower the price, the more happy and PAYING customers. |
I disagree that it is more expensive to make a high quality lens for a larger imager. Panavision stated very clearly that the design of panavised lenses for the CineAlta cameras for Star Wars was difficult and expensive precisely BECAUSE the sensor was smaller. They maintained that the lenses for the CineAlta needed to be BETTER than 35mm.
Plus, there are plenty of very small lenses, even zooms, that are perfectly servicable for 35mm still photography. Are you saying that it would be more difficult to build a similar lens suitable for paltry HD resolutions? I assume that the very expensive broadcast lenses are more expensive because of features like no breathing during zooming, multi-coated elements to prevent internal flaring, precise and repeatable manual control, etc. I don't doubt the superior quality of big brodcast lenses, any more than I would doubt that a Zeiss Digiprime is better than a cheap Fujinon zoom. But... If all other things were equal, why couldn't Sony have put a 35mm-size sensor on the HC-1, for instance? EDIT> Dan(s), I realize that consumer cams have no reason to go this way. In fact, there's every reason to make the imagers smaller. A shirt-pocket cam needs to be whipped out, press the button, and whammo - everythings in focus. More DOF the better. But consumers, by in large, are not going to buy the DVX-100 or the new HVX-200, for instance. I didn't realize the chip fab economics were so restrictive. That's something to think about. I wonder when the economics are no longer an issue, then we will see 35mm sensors as common as 35mm still cameras. |
Cine 35 and still 35 are not the same format. Cine lenses and still lenses are not made the same either.
But basically, yes... cost of chips, cost of lenses, larger format form, more digital storage costs... they all 'get bigger' as the size of the target gets bigger. Look at the reverse 'devolution' of film. In order to put film cameras into the publics hands... they had to make it cheaper. They made it cheaper by making it smaller. First 16mm, then 8mm... smaller and cheaper. If you want to get 'larger'... it's going to cost more. |
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But THEY ARE the driving force not a few passionate and dedicated professionals! OK, not a few, but definitely can't compare the two segments in buying power. For a manufacturer, that's all that matters: to offset the cost of R&D + manufacture and show a trace of profit, right? Otherwise they'd become "passionate" researchers and would be belly up in no time. Quote:
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I just realized I didn't frame this discussion properly. I'm not talking about the Dalsa and Genisis camera sensors, spitting out multi-megapixel data rates. I shouldn't have used them as an example.
I'm simply wondering why we can't have NTSC or even 1080p RESOLUTION sensors, but at 35mm PHYSICAL sizes. That way, we can have the same formats we are using now - DV, HDV or DVCProHD, but with the same DOF as 35mm. I suppose that the wafer size and economics of defects still apply, but I don't want anyone to think I'm asking "why can't I have a Genesis camera under 4 lbs and under $5k". That would be naive. I'm simply wondering why 1/3" is chosen, as opposed to 1/2" or even 1.375". |
I think you know the answer Scott...: PRICE (son-of-a-b-udget)
Panasonic's GS series was the first (I think) to deliver 3CCD under $1K (imagine that!) CCD size? 1/6" ! |
Scott,
On factor is the segmentation of product lines within the manufacturers. I'm sure the DVX/XL engineers would love to put bigger than 1/3" CCD in their products, but likely are prevented from doing so, to avoid competition from the professional divisions of those companies. I'll bet there are policies, memos, etc. within these companies specifically stating that the DVX/XL series go no larger than 1/3". After that, it's pro line. Josh |
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1/2" CCDs are 8mm diagonal. |
Good catch Dan Vance. I figured they meant 1/2" ccd plus .8 something.just from glancnig at the site. Why would you anyone ever put a decimal with a fraction. Isn't the point of fractions not to use decimals, and the point of decimals not to use fraction?
Oh yeah, you seem to be a freakin genius Dan, the camcorder you built looks awsome. The circuit you make with the physical shutter sounded really cool. |
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