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Old Jun 25, 2005, 9:08 PM   #1
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This is a general rant that I am hoping people will comment on. It concerns megapixels and sensor sizes on digital cameras.

A lens system's goal is to accurately transmit light to a sensor. A sensor's goal is to accurately record the light that falls upon it. Once the light is recorded by the sensor it is the camera's job to bring that light to the user in a way that is accurate and relevant to the human eye.

In the digital camera world right now I think camera makers are losing sight of the fundamental job of the camera. One basic reason for this is the megapixel race as it is being played out.

When a camera manufacturer talks about special noise reduction algorithms used in a camera, to me it is an admission that the camera is fundamentally flawed. It cannot deliver an accurate record of the light that falls on the sensor. The image must be "cleaned up" before it is fit for delivery The more a digital image must be processed before it can be viewed, the worse the camera is in my opinion.

To me the reason for much of this post processing is that many camera sensors are too small and packed too tightly with pixels. Small sensor sizes require lenses that are more accurately made than larger sensors, and many lenses aren't up to the job. In addition, on a tightly packed sensor the individual pixel sensors can't get enough light to do their jobs well. So on any given image some of them misfire, creating noise which must be cleaned up.

How much size and space is reasonable? Let's say that a 35mm film camera delivers 12 megapixels of good, useful information. That seems reasonable. You have dSLR cameras that put 8 megapixels of information on a 24 mm sensor. That seems reasonable. But once you leave the dSLR range you get cameras that put 8 megapixels of information on 9 mm sensors. It's common to see 7 megapixel cameras with a 7.2 mm sensor. That doesn't seem reasonable to me.

I'm going to throw in an example here.

Here is a camera with 5MP on a 7.2mm sensor.
http://www.steves-digicams.com/2003_...s/PC040046.JPG

Here is a very similar camera with 7MP on a 7.2mm sensor.
http://www.steves-digicams.com/2005_...s/P3100043.JPG

Here is a less similar camera with 8MP on a 8.8mm sensor.
http://www.steves-digicams.com/2004_...s/p3110170.jpg

Here is a not very similar camera with 8MP on a 18mm sensor.
http://www.steves-digicams.com/2004_...s/P1210482.JPG

I'd rather have the first camera than the second. To me there is a big difference between the third and fourth. You can argue that the lens is different, but remember the larger sensor size means the lens in camera 4 doesn't have to be as precise to get the same results.

Summary:
1. Larger sensor sizes make it easier for both the lenses and the individual pixel sensors to do their jobs.
2. Too many pixels on a small sensor can lead to a lot of noise, which needs to be corrected.
3. The megapixel race is perhaps leading camera manufacturers away from good fundamental camera design.

Suggestion: Start a sensor size race!
1. When a manufacturer boasts about 35mm lens compatibility in their dSLR, ask them when they will have a 35mm sized sensor.
2. When shopping for a good point and shoot, let people know that 7 megapixels is fine but what you really want is an APS sized sensor. Saying APS instead of 25mm will make it easier for the marketing department to comprehend and may provoke a little guilt about digital cameras not measuring up to a good APS point and shoot.
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Old Jun 25, 2005, 10:21 PM   #2
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I've been reading the same rant for years.

Back when 2Mp was the latest and greatest people were saying they had reached the resolving power of small camera lenses and that more pixels would simply be like an upsample without more photographic information. Dpreview does resolution tests on all of their cameras and real world resolution on test charts has climbed steadily with every increase in density.

Back when 2Mp was the latest and greatest the ranters were saying that the density limit had been reached, and that by the time they got to 4Mp with the same sized sensors the noise would be so bad the image would be degraded to the point where it would not be as good as the 2Mp. The 1/1.8 7Mp sensor you listed actually has slightly better noise than the same sized 5Mp. If you don't believe me display them at the same size. You really picked the wrong time for your rant because Fuji finally brought their Super CCD technology to age with a 1/1.7 sensor that has noise approaching DSLR. Now if they would only put it in a camera for grownups.

You are welcome to your APS sized sensor on non-DSLR cameras. Compact APS film cameras typically had maximum F-stops in the 6s &7s. The reason we have pocket cameras with f2.8 and compacts with f2 is that the sensors are small. And the reason they can make reasonably sized cameras with zooms that maintain f2.8 all the way to 12X is because of the small sensors. Nikon put a 2/3 sensor in their 8800 and had to go to f5.3 at 10X, which just about negates the advantage of their stabilization. And that's only 8.8mm in your world. There are no pocket cameras with that sensor because it is too large to be practical.

I've had a large format printer for a couple of years. A 13 X 19 from a 5Mp camera is only in the 135PPI range if you don't have to crop. There has been a definite improvement in print quality since I upgraded my pocket camera to 7Mp.

I had 35mm SLR gear for years. During most of that time I also had small pocket zoom 35mm cameras I could carry with me. Over the years I have more photos from my pocket cameras than from my big gear. The quality wasn't nearly as good, but I had the pictures. The current bunch of pocket digitals puts my small 35mm cameras to shame in size, features and image quality. That is because the sensor designers have been a lot smarter than the ranters.

I have no desire to carry a bag of camera gear around again. If you carry a DSLR with just one lens you can't come near the zoom range and aperture of some of the current prosumer digitals. That is because they have made good progress in increasing sensor density. I know the DSLR gives better quality images. But the prosumer images are quite useable and the cameras more versatile unless you carry a bag of lenses.

I couldn't be more pleased than with my new little pocket camera and my long zoom stabilized prosumer. You can get plenty of APS sized sensors in DSLRs. Once you get the sensor that size you need interchangeable lenses to make it practical, or you will be quite zoom and/or aperture limited. Or have to carry a camera so big you would be better off with the DSLR and bag of lenses.

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Old Jun 26, 2005, 12:09 AM   #3
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I agree with Slipe: I don't give two hoots or a whoopee about either pixel count or pixel size. The quality of the image is what counts. Even though that can become very subjective, noise has decreased and resolution increased over the years and that trend hasn't ended yet.

There will ALWAYS be noise in a digital photo, just as there will always be grain in a chemical photo. It may be so small that you need some powerfull magnifcation to see it, but it is there.

Being able to trade noise/shapness and ISO/noise are features of digital, not a drawback.
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Old Jun 26, 2005, 11:16 AM   #4
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Thanks for your replies! I have learned a lot.

In particular slipe I appreciate your taking the time to "take me to school." Aperture is certainly important, I didn't realize how much small sensor sizes affect that. I'll also pay more attention to the resolution info in dpreview. I am definitely a fan of small cameras and am currently organizing and doing some scans on my small 35mm camera images (Olympus XA 2 and others). I have a small digital camera now and definitely don't want to give that up.

Bill and TD-7900 I agree that things are getting better and will continue to do so. It's my curiosity about the technology that makes me pay attention to some of these things and yes it can be more a distraction than a help when it comes to taking good pictures.
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Old Jun 26, 2005, 12:14 PM   #5
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If they stuck an aps sized sensor into a small camera they would lose all the advantages of being able to use a small lens. To have an (35mm equivalent) 400mm f2.8 on an APS semsor you would need a lens very nearly as big as a 400mm on 35mm, ie at least 15 cm long and more than 1kg. No-one even makes APS lenses in that length because they would be so close in size to a full size lens there would be no point.
An APS point and shoot would be small with a fixed 35mm lens (which would effectively be a 50mm equivalent on a 35mm camera) but who would buy one?
An APS p&s with a 18-200 zoom would be as big as a small dslr with an 18-200 zoom (even the skateboard baggy pants kids would struggle to stick one in their pocket) only without the ability to changes to a different lens.
Small cameras are getting bettter because the improved quality of the sensors is allowing higher iso with less noise. This allows a good image to be captured at a fast shutter speed even with a small lens (and so not much light).
I see no reason why a 7mm sensor won't be able to capture as much information in a few years time as a full size one can now considering the speed of technological advance.
What you won't get back is the small depth of field you can get with a larger sensor. A 7mm sensor needs an f-stop much lower than a 35mm one to get the same depth of field.
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Old Jun 26, 2005, 7:40 PM   #6
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jacks thanks for the reply. Physical size of the lens assembly is an important point. I see that there are small sized APS film cameras available with 3x or 4x zoom lenses. But if a camera maker needs to use a smaller sensor to keep the size of the camera down in say an 8x or 10x point and shoot zoom then I guess it doesn't make good economic sense to use a different, larger sensor in a lower feature, lower cost camera.

TD-7900 That Nikon 7900 looks interesting. I didn't know Nikon made a small camera like that until you pointed it out. 7MP, f2.8, there's a lot to like about that camera. I do have a friend with a slightly larger Sony W7 and that's a nice camera as well. For now I'll stick with my current small camera (Kyocera SL300R) but I can see that small cameras are getting better...
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Old Jun 28, 2005, 8:10 AM   #7
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I think the software in the camera has alot to do with this aswell.

When the 8mp 'bridge' cameras first came out, the UK magazine reviews weren't particularly kind with regards detail and noise. Whereas the 7mp cameras (with the smaller sensor) were concluded to be better in terms of detail and noise. Given that the 8mp sensors have larger photosites - which should yield a technically superior image - I can only assume that the difference is in the camera's software. I would like to see what the Powershot Pro1 is capable of if the firmware were to updated to match the latest Canon digicams.
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Old Jun 28, 2005, 9:06 AM   #8
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Both dpreview and Imaging Resource are usually more interested in the in-camera noise reduction than Steve. It might be more that Steve just reports the image as a little soft and doesn't try to outguess the camera makers for the reason.

But in camera noise reduction softens the image. I wish there was a switch to turn it off. Sophisticated noise reduction software can do a much better job.

I hadn't realized how poor the in-camera noise reduction is until I was running some tests on my new Z750. It has a flash assist that is like a poor man's Shadow/Highlight or contrast mask. I took some flash shots at ISO 50, 100 and auto with flash assist and at the same without it and used shadow/highlight. It was for a discussion on noise to see which approach worked best. Once you pulled them to the same level the noise was about the same – and quite high. I included an ISO 400 shot just for fun. I was amazed that the ISO 400 shot had by far the lowest noise with all brought to the same brightness. But when I zoomed way in I found that the image was blurred. Casio softens the image at high ISO.

I guess it isn't surprising that a little camera can't do as good a job in a quarter second of processing time as a 3Ghz computer running for a couple of minutes doing a sophisticated analysis. I don't mind that they do in-camera noise reduction which is little more than a blur filter for people who aren't into post processing, if I could just turn it off.

Nobody has come up with magic yet for in-camera noise reduction. Apply noise reduction to the Pro1 and you get a softer image – which would be a pity with a camera that I think has the highest resolution of the prosumers other than the Oly 8080. I think it is that the 7Mp chip is particularly well designed and not that the small camera design teams are better than the big camera teams at Canon, Nikon and Minolta. I think the reviewers were expecting less from the little cameras with the 7Mp sensor as well. None of them have quite the resolution of the Pro1, Sony 828 or Oly 8080.


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Old Jun 28, 2005, 10:05 AM   #9
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If you look at the same shot taken on a Powershot G6 and a Powershot Pro1 at 100% in photoshop, the G6 shows less noise and more detail. I don't think it has anything to do with noise reduction as both cameras only apply this on shots of over 1.3 seconds.

What I was referring to was the actual processing of the raw data by the camera as it creates the JPEG. I think the processing software has been improved somewhat, as the Pro1 shots are a little blotchy close up like my old Kodak was.

A sure way to tell, would be to try a RAW capture with the Pro1. This would let us know how much of the noise is due to the processing or the sensor.

slipe wrote:
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I think the reviewers were expecting less from the little cameras with the 7Mp sensor as well. None of them have quite the resolution of the Pro1, Sony 828 or Oly 8080.

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Old Jun 28, 2005, 10:43 AM   #10
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The dark mask subtraction used for long shutter shots is for a different kind of noise. It is pretty effective compared to what the shot would look like without it and doesn't seem to blur the shot. But many cameras use in-camera noise reduction for normal noise. Read Dave's review of the P200 at Imaging Resource where he compares it to the P150 with less in-camera noise reduction. Both Imaging Resource and dpreview often comment that they think the in-camera noise reduction is too high in some of their reviews. My Z750 definitely applies noise reduction for ISO 400 shots.

In absolute resolution the G6 is 1600 horizontal and 1500 vertical. The Pro1 is 1700 horizontal and 1650 vertical. This is from the dpreview resolution tests. I can't comment on the blotchy as some people see blotchy when I don't – it wouldn't be the first time I was accused of being insensitive.

If there is noise reduction converting from raw to JPG it blurs the image. Even sophisticated noise reduction programs blur the image a little. But the trade-off is acceptable to me if the settings are kept subtle and you use a plug-in so you can avoid edges and treat areas like sky differently. The trade-off isn't acceptable to me for in-camera noise reduction and I wish I could turn it off on cameras that use it. I prefer full sharpness with the noise and I can take it out myself if it is too obnoxious.


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