Professional lenses with built in sensors
A friend (Larry P.) suggested that the time was here for serious (ie. DSLR) cameras to undertake a design revolution. The old SLR design, with a mirror that flips up and must sit between the last lens element and the sensor, creates a lot of problems in designing the lens and camera systems. Yes, being able to view directly through the lens with your eye is a very useful thing. But at what cost?
We're already seeing the disappearance of optical viewfinders, even rangefinders, from small consumer cameras, if only to save space. Few people were using them any more, since the screen display turns out to show a lot more, and is even better than the eye in low light.
Serious cameras aren't seeking (too much) to save space. We want image quality most of all, and the tools to shoot good images. Looking through the viewfinder is one of those tools, but again, at what cost?
So a proposal is put forward that now that sensors are dropping in price -- even full frame sensors -- that each lens have its own sensor, and shutter, that is part of it. There would be a body which has a digital (and mounting) connection with the lens. The body would have display, processor, controls, battery and so on. It's a pretty radical proposal. Let's look at the advantages:
- There is much more freedom in lens design, and lenses can be smaller, less expensive (for the lens at least) and lighter.
- Each sensor can be custom fit to the lens and its image circle. Some lenses could have small sensors and some have large ones. You could work with both super large hi-res sensors on a 28-70mm zoom, and also carry a small, dense sensor which offers you a (higher noise) super-tele in a tiny package.
- Each sensor can be tuned to the flaws of a particular lens, ready to correct distortions and other problems. (This could be done with a protocol for communicating those distortions to the camera too, and we're finally starting to see things like the 5D's database of lens light fall-off.)
- You would not get dust on the sensor
- You could build special bodies and/or lens holders that could hold multiple lenses, as now there is only an electronic connection to each lens. As a result you could switch among lenses instantly!
- It might be possible to have standarization, so you could mix and match lenses from different vendors as you choose.
- Image stabilization designs could be done with both sensor and optics, whatever works best.
- The lens could be some modest distance from the "body."
- Body design can also be liberated, as the mechanical linkage with the lens can be designed without the need for a light path.
There are some downsides
- Obviously, sensors are not yet so cheap that this isn't a more expensive approach initially. But serious lenses are often more than $1,000 and this approach might not increase their cost by more than a few hundred dollars. For cheaper lenses, putting on a high quality sensor would not make sense, cost-wise.
- In turn, where now you might put a lot of money into your one sensor, here it must be spread.
- Today, if you get a new body with a new sensor, you now get the better sensor with all your lenses.
- You lose the TTL viewfinder and focusing screen.
- You need all new equipment, and probably want new mounting hardware too.
Sensors may not be cheap enough to do this today, but they are getting cheaper, and thanks to Moore's law this will continue. We've pretty much got all the megapixels we want now, so the main focus will be in improving sensor quality and ISO speed. Until sensors get so cheap that we might buy several that we know will be obsolete in a few years, one approach would be to still have a mount, so that sensors on a lens can be change. However, this need not be a quick disconnect mount, it would be more intended so you could swap out the sensor on a lens.
And of course, there could be a "sensor" on the lens which is not a sensor, but rather a mount to go on a body with a sensor, as we have today. However, this would have to be a body without a flip-up mirror, as the focal planes of these lenses would be much closer to the last lens element than they can be with an SLR. And I could also see the potential of a super-fancy rangefinder, which uses its own lens, but is digitally tied to focus and other information from the real lens to give you a view identical to the main lens, though DOF preview and manual focus would still be best on the screen.
Aside from the option of better lens design (and thus better image quality for the money) the two most appealing features to me are the instant electronic lens switch, and the ability to use different size sensors. Much as I would like to, even if I wanted to pay $6,000 for one of those amazing super-tele fast lenses that sports photographers use, I would only carry it around rarely. On the other hand, I might very well carry a short 85mm lens with a small sensor of the sort found in P&S cameras that gave me the field of view of a 600mm lens with 10 megapixels. It's going to get me photos I would not otherwise get because I'm just not going to carry a 600mm f/2.8 in my bag. Instant lens switch might also change your desires about what zooms you want, since one of the goals of a zoom is to switch focal lengths quickly, though another goal is to have fewer lenses in the bag. If not using a mount that holds multiple lenses, lens switch could still be a very quick unsnap/snap, with no caps to remove and no seal to make.
Of course, to do this would require a very high-bandwidth data/control/power bus that ideally was standardized over vendors and designed to be upwards compatible with the future, faster bus that might come along. There is already a Camera Link bus specification, but the technologies behind SATA-600 (also 6gb) or 10gig ethernet might make sense.
So I suspect that as sensors get cheap enough, we might see things move this way.
Wide angle lens
Let's consider how this might help us produce a wide angle lens. Good wide angle lenses are expensive. It takes work and good design to keep them free from distortions, vignetting and to make them rectilinear with a flat focal plane. Flare is also always a problem, as is doing all this for a sensor that is far from the last element. And these things are hard to do for a big image circle, though smaller image circles require very short focal lengths.
A sensor-included wide-angle could select the right focal length and image circle to get the best price/performance at suitable low noise. The sensors's pixels could sit in distorted rows to match the distortions of the lens -- indeed, one could go all the way to a fish-eye lens and put a fish-eye sensor on it to make it rectilinear. (This could also be done in software with some loss of sharpness.) The sensors could be designed so that they are larger (or have larger covering lenses) at the corners, to perfectly account for vignetting. And of course, one could use the short-focus design common in view cameras that can't be done in SLRs because the focal plane is so close to the last lens element.
It's not out of the question that such a lens/sensor could even be cheaper than a high quality lens able to put a great image on a 36mm full-frame sensor, and take better photos.