Tuesday, 24 March 2009

digital camera evolution

Some things seem to be coming together at the moment in digital cameras to perhaps give us something many of us have been looking for in a digital camera; compact and high quality.

Readers of my blog will know that I value a compact camera for hiking and that I also like images of high enough quality that I don't feel tempted to be dragging along my 4x5 camera.

I've been very keen to see results of the new Panasonic G1 as a great light weight camera for hiking that doesn't have the bulk of the traditional DSLR.

Reading the latest tests on DPReview for this camera make it clear that it makes images which at may rival full frame DSLR's such as the 5D. I can wel understand why some people may be skeptical, so I thought I'd put together a few views on "how can it be so".

There are some points which need to be considered in understanding how digital cameras are presently and how they may be (without technology changes) for example:
  • resolution of DSLR cameras is often sensor limited (meaning higher density will reveal more of what the existing lenses can produce
  • manufacturing sensor density is already at its peak (particularly in the case of compact cameras)

many of the APS sensor DSLR cameras (and some of the full frame ones) were until quite recently limited in how good their images can be due to the limits of the sensor. Even full frame cameras like the 5D which can record about 50 lp/mm still don't record what the best lenses will produce. So your camera may not be able to record the image quality that the lenses can deliver. A quick peek at DPReview will show that with the same lenses images from (for example) the Canon APS series (10D, 20D, 40D, 50D) have been showing more and more details as sensor density increases.

This means we need higher packing density than the DSLR's are giving.

So, how high density can we have on our sensors?

Well right now have the ability to pack very high, with (especially compact) digital cameras being so high that we are hitting limits. The problem is that the photo-sensors are now getting so small (due to packing density) that this is effectively a limiting factor because they are not getting enough light hitting them (compare a bucket in the rain vs a thimble, while the thimble won't get filled the bucket will perhaps get a deeper amount of water in it than the height of the thimble).

So after sensor densities get higher than a certain size the amount of noise gets higher than you would want. So there comes a trade off point where you can't pack them any more and to get images of higher quality you need to get a bigger sensor.

Where might that be?

Now, when it comes to low noise images my old 3 Megapixel Coolpix 990 was pretty good, and my Coolpix 5000 at 5 Megapixles was good too. But my Canon A520 which is newer produces noisy images which are dreadful. Its interesting to note that the A520 has a much smaller sensor and thus a higher pixel density than the Coolpix.

So this gives us a kind of empirical measure of the limits. The A520 is about 16 MP/cm² in packing density while the Coolpix 5000 is more like 5 MP/cm².

Some time ago I wrote a page about image noise in digital cameras, in this article I explored the issue of image size vs sensor size as well as that of image noise comes from JPG processing over RAW post processed on a PC images. In that page I suggested that as :

.. the camera image sensor sizes are:

CP5000 sensor size = (8.80 x 6.60 mm) with an image size of 2560 x 1920 pixels
20D sensor size = (22.5 x 15.0 mm) with an image size of 3504 x 2336 pixels

This gives the CP something like 290 pixels per mm of sensor and the 20D about 156 pixels per mm of sensor.

Following this 'calculation' I guesstimate that for a sensor the same size as the 20D could get (22.5 x 290) x (15 x 290 ) = 6525 X 4350 pixel area if packed to the density of the CP5000.That's about 28 Megapixels.

So if you take this that I felt that at 5 MP/cm2 5000 was a reasonable upper limit of packing density VS noise tolerance. This means you could make an APS sized sensor DSLR's that would make images equal in per pixel quality to the Coolpix 5000 as big as as 28 megapixels.

Given that the Canon 50D is already 15 megapixels I don't think this metric is out in space cadet world.

So where should we go from here?

This is where my present highly desired camera (the Panasonic G1) comes in. Sitting nicely in the middle of the balance of compact size / smaller sensor / reasonable packing density. It has enough size to allow big photo sites and high enough packing density to make use of high resolution lenses.

With a 10Megapixel output, and a packing density of around 5 MP/cm2 its not that far from the latest Canon 50D (which works out to be 4.5 MP/cm2), yet its all in a nice compact device which weighs less than 1/2 the 50D.

To the left I put this into a table to show the increases over successive models.

Looking at this table the G1 produces nearly the same number of pixels as the 5D and with 4 times the packing density should be able to reveal more of the details captured by the lenses.

Now, of course there are still has many advantages in the bigger and denser sensor, for example there are now some some pretty hot processing applied to push its high ISO performance to 6400 ISO (and wow, isn't that hot! think for a minute regular film is 100, 200 or 400. 800 used to be as grainy as all shit. 1600 was barely usable and I've never even heard of anyone using 3200 or 6400 in film). But how many of us want to process 21Megapixel images or spend $8000 to get it? Maybe sometimes, but seriously it really consumes memory and resources and I can get a 6x12 120 for much less.

Getting back to the comparison of the G1 with the 5D, it still has a lower density than my older compacts (so noise should be acceptable) and we can also expect that will make images which should be clearer the 5D because it can make better use of higher resolution lenses than the 5D can.

To give a comparative feel here the G1 sensor is a wee bit smaller than APS (the rectancle in green) and about 1/2 the size of 35mm (width or height) making it heaps cheaper to make than the 35mm.

So this (in my opinion) adds up to what we see: a cameras being significantly smaller than APS cameras (like my 10D), having ability to resolve more from the lenses and with a low price point.

I think that the Panasonic G1 is at about that sweet spot between the highest density for resolution and noise. The only way to get better will be to put in a bigger sensor.

I'll go out on a limb here and say: without a major paradigm shift in technology I think we're pretty close to the limits of technology and won't see much in change from this point ... for the next few years at least.

1 comment:

Charles Maclauchlan said...

I certainly understand your logic. I couldn't understand why digital cameras continued with the mirror box design established in the 1950's...to keep selling lenses perhaps. Searching for an alternative I even briefly considered a Leica but to afford it I would have to give up too many things...like eating or paying rent.

The Sigma DP1 came along before the Panasonic G1 and so I bought one, almost a year ago. Using this camera has changed my style. I shoot more like I did with film, more thinking, fewer images, but the images are wonderful.

The size is substantially smaller than the G1, I often carry the DP1 in my shirt pocket. Interestingly I am usually ignored when using the camera...it causes less concern than a DSLR.