the one feature I want in a dSLR. . .

[Graham Welland]

Now that Sony has killed their superb fixed-lens R1, and no one else is producing such a large sensor fixed lens zoom, my hopes for someday upgrading to a 20+ MP R2 or R3 lie in ruins.  That's too bad, as the ultra short backfocus lens design has some real advantages over SLR lens mounts.  However that is not my primary reason for choosing the R1 over a dSLR.

What I want is a live LCD higher megapixel camera.  The advantages of composing with the LCD instead of an optical viewfinder are numerous:

1) autofocus using a slower but more reliable contrast-detection system for landscape shooting (never any front/back focus issues).

2) You see the cameras sensor image with its limitations on DR instead of your eye with unlimited DR.  Thus you get a sense of the captured file.

3) Camera does not have to be glued to your face!  Makes shooting at kids eye level easier, frog eye level MUCH easier!  Composing landscapes can be done with both eyes open, looking at the scene and at the image instead of peeping through a tunnel.  No need to crouch down to tripod height if you are shooting low, and you can use a very tall tripod and see what you are composing.

4) Get your exposure right the FIRST TIME, EVERY TIME with a live histogram.

5) Of course, the camera should ALSO have a standard mirror and standard dSLR autofocus / metering for all the times when the TTL optical view is an advantage.

6) Video.  While the R1 does not allow video recording, virtually all other fixed-lens live LCD digital cameras do.  This is a great feature to have, and should be included in future digital cameras.

Olympus has done most of this this with the E330 and Fuji to a lesser extent with the S3.  I believe even one of the Canon astrophotography cameras can do some of these things.  Come on, let's add this to all dSLRs.  Geez!  I feel that Canon and Nikon are stuck in some kind of time-warp with dSLR design, totally unwilling to do anything truly innovative, perhaps out of fear that their customers are too hide-bound to appreciate it.
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I'm not a fan of EVF for many reasons, even with the R1 which I owned previously. However, I'm surprised that Nikon/Canon haven't yet found a way for a hybrid viewfinder that could overlay a live histogram alongside the optical viewfinder image. Now THAT would be a killer application of EVF technology that would help with accurate digital metering!

[Ray]

I can only repeat my main point from above: rather than thinking in terms of what you would prefer, without having had any experience using such equipment or in professional video photography, I invite you to consider what a great number of people far more knowledgeable than you or I have chosen, and try to understand why. By the way, have you actually seen a lot of "dark and grainy footage" from professional video cameras?
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You are straying off the point, BJL. Of course there might be good technical reasons why this feature I'd like is not available; reasons which I don't understand.

I'm merely making the reasonable observations that:-

1. 'Still' image quality from P&S cameras, whether from 1/2.7", 1/2.5" or 2/3" size sensors, is not as good as it is from the larger DSLR sensors.

2. Video quality from P&S 'still' cameras is not as good as it is from cheap, consumer grade video camcorders with similar size sensors to the smaller variety of P&S still cameras.

3. On the face of it, it would seem possible to use the higher picture quality status of the larger DSLR sensors to produce better quality video than is currently available from consumer grade videocams. This is a feature I would like and I wonder why it's not being offered.

So far, the most convincing reason that's been mentioned in this thread is a possible overheating resulting from a large sensor running continuously.

[BJL]

You are straying off the point, BJL. Of course there might be good technical reasons why this feature I'd like is not available; reasons which I don't understand.
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I thought that the point was to try to understand the clear fact that no digital motion picture camera uses a format nearly as large as the "36mm wide" that you propose. (Frame width seems the safest measure, as aspect ratio is often adjusted by a vertical crop). Indeed, even the largest current format, the roughly 24mm wide "movie 35mm" of the Panavision Genesis, has been ignored by the world of HD video and makers like Sony, Panasonic and Canon in favor of options like 3 CCD 2/3" format, about 9mm wide.

One important pont is that Panavisio has shown th technical feasibility of a format larget than 2/3", and yet it has been adopted on only averyt limited basis. THis alone should be enough to dismiss the myth about larger sensors generating too much heat in video mode. Anyway, it should be clear that there is plenty of room for active cooling in a unit the size of a professionbal video camera. A final piece of evidence: the Olympus E-330 has a live video mode using a sensor four times larger than 2/3" format without problems of overheating or excessive power consumption.

So once again I come down to one main explanation:
1. the advantages of the larger format largely relate to better low light performance and lower minimum DOF.
2. These rely on using lenses with both longer focal lengths and larger maximum aperture diameters.
3. The larger maximum apertures in particular come with disadvantages in cost, size and weight.
4. These disadvantages, probably size and weight more than cost, are judged by the industry to be too great to justify the advantages in most or all situations.

The issue here is one of balancing advantages in both directions, bearing in mind the law of diminishing returns. This is the common pattern that as you go further and further towards an extreme (like ever larger or smaller sensors and photo-sites), each subsequent step brings less increase in advantages than the previous step, and more increase in disadvantages, with a given level of technology. (technological progress can diminishes the disadvantages in each direction, so there is perhaps no universal answer as to which way it shifts the balance.)

This means for example that it is invalid to argue for the superiority of one option over others by pointing to the clear disadvantages of a format that is far smaller or far larger than any the options being considered. The hopefully obvious disadvantages of making a 1920x1080 video camera in "Hasselblad 48mm format", giving 25 micron wide photosites, are irrelevant to the comparison of format and pixel size options like 4.7 microns (2/3"), 12 microns (the 35mm format Genesis) and 18 microns (36mm wide used with 1920x1080). Equally irrelevant is evidence of the disadvantages of the far smaller 2.3 micron pixels of three year old sensor in the Sony T1. More so when you consider that 2/3" format HD video uses three CCDs, with no color filter arrays or Bayer interpolation, so the advantage in sensitivity over the T1 is greater.

P. S. The video quality advantages of a video camera over video from a still camera of the same sensor size seem easy to explain: the still camera sensor has far more, far smaller photo-sites, and then probably uses sub-sampling to get down to video pixel counts. That is, reading only some of the photo-sites. To get the higher video frame rates, either this sub-sampling or on-sensor binning is needed, and binning s not yet done in digicam interline CCDs as far as I know.

That means that the still cameras' video modes have the limitations of their smaller photo-sites compared to the video cameras, with the expected lower sensitivity and dynamic range. It could be a different story in the future with on-sensor binning, which Foveon offers in its X3 CMOS sensors, and Kodak is now offering in Bayer CFA interline CCDs. (Up till now, binning has been monochrome only, possible for example with three CCD video cameras.)

[Ray]

I thought that the point was to try to understand the clear fact that no digital motion picture camera uses a format nearly as large as the "36mm wide" that you propose.

BJL,
With all due respect, that's not the point. I don't think I have anywhere suggested that an add-on video feature in a DSLR would make all professional video recorders redundant. It might well be true that there are very few professional HD videocams that have sensors larger than 2/3". So what? There are also very few 1-2mp 'still' cameras that have sensors larger than 2/3rds. What's the point of designing something that is unnecessarily cumbersome and expensive and which produces a quality that far exceeds the requirements of the end user??

I believe that until recently most professional video recorders have produced anamorphic 1440x1080i images, which are smaller than 1 megapixel. TVs and video projectors capable of displaying 2mp images are now gradually becoming available and more affordable. There's no mystery here as to why videocams do not use sensors larger than 2/3rds.

My experience with video capture is as follows. Standard definition camcorders that claim to offer 'near broadcast' quality are far from broadcast quality. The image stabilisation in such cameras often works on a 'pixel shifting' principle which unavoidably reduces even further what is already poor resolution. Performance in excellent lighting conditions is hardly acceptable and in less than ideal lighting conditions, woefully inadequate.

A similar situation exists with the add-on video feature in P&S still cameras, except it's generally worse.

So, the point for me is to try to understand the technical difficulties that have prevented manufacturers of DSLRs from offering the same add-on video feature that most P&S cameras offer, but with correspondingly higher quality. You cannot fit 2m 5D pixels on a 2/3rds sensor let alone a 1/2.7" sensor. Even without binning, there should be a significant advantage. Most consumer grade videocams do not use 3 CCDs per pixel.

The reasons that seem likely are: 1. Overheating, without additional technology to combat it, which would no doubt add to the weight, bulk and cost of the camera.

2. More processing power and speed, parallel processing etc. which again adds to the cost.

3. The consumer grade camcorder market would take a big hit if this feature were implemented in the way I've suggested.

A final piece of evidence: the Olympus E-330 has a live video mode using a sensor four times larger than 2/3" format without problems of overheating or excessive power consumption.

I presume this is standard definition video. If the quality is better than the video from a consumer grade camcorder, then that would be one good reason to buy an E-330, wouldn't it.  

[Ray]

BJL,
Perhaps once again such arguments can be reduced to lens quality. We've had many discussion before about aberration limitations in lenses. Are general purpose videocam lenses superior to Canon prime lenses, at f1.8 for example, or, if good DoF is required, at f8 (ie. videocam f1.8 compared with 35mm f8)?

We know that at low resolutions, 10 lp/mm for example, that good 35mm lenses are up in the MTF 90%+ range. Is much improvement possible here?

Consider the flexibility of CMOS sensor design with on-board processing. If all we're interested in is a 2mp image from a 12.8mp 24x36mm sensor, then (potentially) we have a choice of which pixels are going to be accessed. If we start from the outer edges of the sensor, then we have the full focal length of all our 35mm lenses.

If we grab 2m pixels from the centre of the sensor, we have the advantage of better resolution and an effectively greater focal length. According to my calculations (and I know maths is your strong point, so if you correct me I shall not be insulted   ), 2mp in the centre of a 5D sensor occupies an area of 9.4x14mm. My 400mm lens becomes a 1000mm lens in video mode.

But I have a choice, if the camera design offers a choice, of which pixels are going to be active when I shoot video. My 15mm Sigma can be either 15mm or 37.5mm, depending on which button I press.

These possibilities seem under-exploited, in my view, and I have a strong hunch the obstacles are not entirely technical.

[Ray]

A final piece of evidence: the Olympus E-330 has a live video mode using a sensor four times larger than 2/3" format without problems of overheating or excessive power consumption.
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I think I've misunderstood you here, BJL. I've just searched the net for comments on the video capability of the Olympus E-330... and of course it doesn't have one.

Your point was, I guess, that in order to get a live preview using the EVF that comes with the E-330, the sensor has to be continuously active, and that that doesn't appear to cause overheating... which sort of gets us back to square one (although a 5D sensor is 4x the area and heating might well be a problem).

All I can say is, if the future 16mp upgrade to the 5D contains a sensor that can access even 1mp of image information through a variety of spacing options, in order to deliver 1280x720p video footage at ISOs up to 3200, then it'll be on my shopping list. I'll consider it a very desirable item, although 2mp would be better.

A quick calculation of the zoom range with any prime lens attached to such a camera gives me a figure of around 4.5x with a 1280x720 16:9 aspect ratio.

My 50/1.4 prime effectively becomes a 50-225mm zoom, but perhaps not continuously adjustable. Anyone fortunate enough to own the Canon 600/4 gets a 600-2700/f4 zoom.

Someone point me in the direction of the patents' office   .

[BJL]

Your point was, I guess, that in order to get a live preview using the EVF that comes with the E-330, the sensor has to be continuously active, and that that doesn't appear to cause overheating... which sort of gets us back to square one (although a 5D sensor is 4x the area and heating might well be a problem).
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I was of course referring to the E-330's video output from the sensor to the LCD (or to an external monitor. Surely that continuous operation generates as much heat (or as little) as if the sensor output was being recorded. (Aside: I imagine one could record the video output used for an external monitor if one wished, but that output is probably sub-sampled, so not of particularly high quality for recording purposes.)
And as far as sensor heat as an explanation for the dominance of formats 2/3" and smaller, you would need to explain first why not even formats like 4/3" and movie 35mm are not used in HD video, given evidence that those sensor formats do not have a significant heating problem.

I suggest we apply Occam's razor, in the form that common phenomena are most likely explained by common causes. The common phenomenon I refer to is an overall shift to smaller formats, with both still and moving pictures, and with both electronic sensors compared to film (or analogue vidicon tubes), and also with film over the decades.
Sensor heating cannot explain all of the downsizings, and nor can price difference dues to sensor costs (including film and processing), since that price gap went down over the years with film, not up.

The only likely common cause I can see is the opportunity to use smaller, lighter and likely less expensive lenses as resolution and sensitivity of the light sensitive media improves.

if the future 16mp upgrade to the 5D contains a sensor that can access even 1mp of image information through a variety of spacing options, in order to deliver 1280x720p video footage at ISOs up to 3200, then it'll be on my shopping list.
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Indeed, maybe DSLR's will add video recording modes, if and when live video preview becomes more popular, and color binning becomes available.

[Ray]

I suggest we apply Occam's razor, in the form that common phenomena are most likely explained by common causes. The common phenomenon I refer to is an overall shift to smaller formats, with both still and moving pictures, and with both electronic sensors compared to film (or analogue vidicon tubes), and also with film over the decades.

BJL,
If I apply Occam's razor, the answer I get is, 'you don't need a large sensor to produce a 2mp image which ends up being highly compressed'. If the current Canon G7 were a 2mp camera instead of a 10mp camera, and in 16:9 format; if it could produce 1920x1080p video at 30fps instead of its actual 1024x768p at 15 fps, I think the buyer would drool over such video capability.

It doesn't seem an impossibly big step to go from 1024x768 at 15fps to 1920x1080 at 30fps; about 3x the processing power/speed, wouldn't you say? Of course, maximum print size from a still image at 240ppi, without interpolation, would then be just 4.5"x8". I don't think anyone would produce such a camera because of this limited print size and whilst the video quality would be outstanding, dedicated videocams would be more flexible and easier to use. The G7 doesn't allow optical zooming in video mode, for example.

Since you've discounted 'heat build-up' as a major technical obstacle to video from large sensors, then applying the Occam's razor principle to the question, 'Why isn't a high quality video mode made available on DSLRs, which could take advantage of low light situations?', I arrive at the answer: because it would cannibalise the profits of consumer grade videocams already being offered by the same manufacturer.

[BJL]

... applying the Occam's razor principle to the question, 'Why isn't a high quality video mode made available on DSLRs, which could take advantage of low light situations?', I arrive at the answer: because it would cannibalise the profits of consumer grade videocams already being offered by the same manufacturer.
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I see another explanation as far more likely, partly because the need to compete with other companies usually precludes the idea of deliberately withholding an attractive feature.

The standard SLR approach relies on having the mirror down for (phase-detection) auto-focus and light metering, and then raising it to make the exposure. This is not compatible with video operation, unless you only focus and meter before the start of a "take". To support video recording from the main sensor of an SLR, changes are needed, and the options I have heard of are
1) Change to doing AF and metering with the sensor, requiring a change to contrast detection AF, which is generally considered inferior to SLR style phase detection AF. This might be appropriate for entry level models aimed at those stepping up from fixed lens compact digicams but not for the more discerning "5D" crowd.
2) Use a partially reflecting mirror ("pellicle mirror"), reflecting enough light up to the AF and exposure meters and maybe to an optical VF, while letting a good proportion of light to go to the sensor. (Canon used a fixed pellicle mirror system in one high frame rate EOS-1 film camera, but dropped it in the more recent model.) For still photography, the camera could have the traditional option of swinging the mirror up, if the benefit of letting all the light go to the sensor is sometimes significant.

[Ray]

To support video recording from the main sensor of an SLR, changes are needed, and the options I have heard of are
1) Change to doing AF and metering with the sensor, requiring a change to contrast detection AF, which is generally considered inferior to SLR style phase detection AF. This might be appropriate for entry level models aimed at those stepping up from fixed lens compact digicams but not for the more discerning "5D" crowd.
2) Use a partially reflecting mirror ("pellicle mirror"), reflecting enough light up to the AF and exposure meters and maybe to an optical VF, while letting a good proportion of light to go to the sensor. (Canon used a fixed pellicle mirror system in one high frame rate EOS-1 film camera, but dropped it in the more recent model.) For still photography, the camera could have the traditional option of swinging the mirror up, if the benefit of letting all the light go to the sensor is sometimes significant.
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Well, I agree that design changes would have to be made and that would probably increase the retail price, but probably not by nearly as much as the additional cost of a separate, high quality videocam. The option I would prefer is mirror lock-up for video mode, rather than a partially reflecting mirror which might reduce sensitivity or increase noise at high ISOs, and a secondary AF and metering system. The review LCD on the back of the camera could act as the live preview and EVF in video mode.