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DPChallenge Forums >> Hardware and Software >> Sensors, Pixel Size and Image Quality
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 01/11/2007 11:13:30 PM · #1
Hello fellow DPC'ers - time for a technical question to the experts.

I recently purchased my second DSLR, a new Sony Alpha A100. It uses a standard APS-C Sensor Size, at 10MP resolution. The Nikon D200, uses the EXACT same sensor as the Sony, also at 10MP resolution. However, the Nikon is nearly three times the cost of the Sony.

Digital photography experts say that the Pixel Size and spacing (resolution) is what determines how much noise and dynamic range an image will have. The smaller the pixels, or the closer the spacing, the worst the image.

So, here's question 1 - Since both cameras have the exact same sensor, pixel size and resolution, does that mean that both cameras will produce the same quality images?

If that is true, then what about Nikon's flagship camera the D2X? It has the same exact size sensor, but has a higher 12mp resolution. That means it has smaller pixels, spaced closer together. So, question 2 - Does that mean that the image quality of the Nikon D2X would be less than the Nikon D200 or Sony Alpha?

And finally, if the above two questions are true, then what is the advantage of buying a more expensive camera if the image quality is the same? How much impact does the lens quality play in the quality of the image?

Thanks for any help you can provide. Sometimes digital photography can be very confusing, especially when to comes to selecting the right equipment.
 01/11/2007 11:15:38 PM · #2
look forward to seeing the responses to this.
01/12/2007 12:44:38 AM · #3
From memory the Nikon D200 and Sony A100 use different sensors.

The main difference being the number of output channels, from the sensor. The sensor of the D200 has 4 channel readout and the one in the Sony has a 2 channels readout. This affects speed at which the data can be written off the sensor and is the reason why the D200 can shoot at 5fps and the Sony only 3fps.

As far as noise per pixel density goes they're likely to be very, very similar in RAW numbers. DSLR's do however include some noise reduction routines in-camera and just how much is done is based on decisions by engineers when designing the camera. Designers need to balance how much noise reduction will be used Vs how much fine detail will be lost.....and still produce an acceptable looking image.

Pricing ? Well lets just say that manufacturers will generally sell for as much as they can get away with.

bazz.
 01/12/2007 12:57:53 AM · #4
"Interpolation algorithms...vary from manufacturer to manufacturer. This is one (of many) reasons why cameras from different manufacturers can have substantial differences in image quality, even if they use the same sensor" - Vincent Bockhaert
 01/12/2007 09:23:08 PM · #5
Originally posted by sir_bazz:
From memory the Nikon D200 and Sony A100 use different sensors.

bazz.


Just an FYI. Sony has been making sensors for many Nikon cameras for years, and they actually selected the sensor they have been supplying Nikon for the D200, for the Sony Alpha A100. However, there might be some other specification that were changed in the two production lines that makes a difference. Vincent's comment about the interpolation algorithms (and other reasons), may explain the image difference.

Thanks again for sharing the knowledge.

Message edited by author 2007-01-12 21:26:55.
 01/12/2007 10:04:44 PM · #6
Originally posted by jlfarrell:
and they actually selected the sensor they have been supplying Nikon for the D200, for the Sony Alpha A100. However, there might be some other specification that were changed in the two production lines that makes a difference.


Strange that Sony would say that as they are clearly different sensors. Different number of readout channels and different number of total pixels. All that appears common is the total number of effective pixels and the sensor dimensions.

DSLR-A100 10.8 million total pixels and 2 readout channels
D200 10.92 million total pixels and 4 readout channels.

edit:
"A100/D80/K10D use the Sony sensor with part # ICX-493AQA
D200 uses Sony sensor ICX-483AQA"

Interpolation will affect jpeg properties if left to the in-camera routines and algorithms but shooting RAW and using a common RAW converter like ACR will remove those differences.

Many people prefer not to rely on the processing algorithms that came "bundled" with our cameras and part of the reason why we prefer RAW.

bazz.

Message edited by author 2007-01-12 22:16:45.
 01/12/2007 10:24:24 PM · #7
There's lots to a camera besides the sensor. AF systems, mechanical systems that affect frame rate and synch speed such as shutters and mirrors, buffer capacity and write speed, body robustness... the list goes on.
Let's assume that the basic sensor is in most respects the same. Even if we discount all of the above, the image quality can be affected by the technology put into the microlens system, the AA filter and the hot mirror, as well as the sophistication of the signal readout and processing (including noise reduction and interpolation algorithms).
So in the end, just because one camera has the same sensor as another does not mean that it's even in the same league. That all said, I'm sure that the image quality is fairly similar between these two cameras, and also sure that the Sony is a great value for the money. Sony *must* bring a really good value to the markeplace or they will not gain market share. Unlike Nikon, which has the name and reputation as one of the market leaders, ans so does not need to price so aggressively.
 01/12/2007 10:35:44 PM · #8
Originally posted by jlfarrell:

Digital photography experts say that the Pixel Size and spacing (resolution) is what determines how much noise and dynamic range an image will have. The smaller the pixels, or the closer the spacing, the worst the image.


Logically thinking if two sensors are the same size, then more pixels = more information. And that is good. Now hopefully that information is good and not noisy or otherwise poor.

Originally posted by jlfarrell:
So, here's question 1 - Since both cameras have the exact same sensor, pixel size and resolution, does that mean that both cameras will produce the same quality images?


Not exactly. The sensor by itself may be the same the rest of the camera has lots to do with the final image. It could be anything from the electronics that connect the sensor to the camera's processor or the lens used.

Originally posted by jlfarrell:
And finally, if the above two questions are true, then what is the advantage of buying a more expensive camera if the image quality is the same? How much impact does the lens quality play in the quality of the image?


Well the D80 and the Sony are not the same camera. Hold them, play with them, drop them if you like and I am sure you will see why one costs more. Plus you need the D80 to use Nikon's superb lenses. Oh and having your camera say Nikon or Canon on the front is way cool.

How much does a lens matter in terms of the final image? Lets say 100%. If your lens sucks, then you can have the best sensor in the world and you image will suck. This should be a major consideration when purchasing a DSLR. What lenses are available and are they good or bad. I am not saying Sony offers crappy lenses but I know that Canon and Nikon offer superb lenses in almost any focal length and if you choose Sony or any other DSLR, you will be missing out on these great lenses.
 01/12/2007 11:08:32 PM · #9
As far as price, I believe the Sony has a less expensive pentamirror. The D200 and D80 use a Pentaprism, which produces a brighter image in the viewfinder. That's also one of the reasons I am moving away from the Canon XT (Pentamirror).

I was looking at the Sony because it has built in IS, but then I got interested in the quality of the viewfinders. Those shopping might want to pay attention to viewfinder magnification, which is often cited in reviews but I had never really paid attention to before.

On a side note on the Alpha: In the store, I got the feeling the Alpha was slow autofocusing compared to the D80, but that might have just been with the kit lens. The latest Pop Photo review rated Alpha as the fastest at autofocusing compared to the D80, Rebel XTi, Pentax K10D, and Samsung (same as the K10D). See that review for more "operational" and quality differences (latest Popular Photography).


01/12/2007 11:24:24 PM · #10
Everyone has given some really good information, and it's greatly appreciated. I think I can clearly see now that there is MUCH more to getting a high quality image than just sensor size and resolution.

I also agree that Canon and Nikon have some superior lens. In fact, really high quality Canon and Nikon lens cost more than my entire Sony Alpha setup.

So, I would have to summarize that, "generally speaking", you get what you pay for. Due to all of the many technical factor and variables involved in digital photography, you can't spend $1,000 on a DSLR and expect to get the same results as a $5,000 DSLR. However, I will have to wait until my photography skills improve enough before I can justify moving up to the Semi-Pro or Pro level equipment.

Thanks to everyone again for sharing. This was a very helpful thread.
 01/13/2007 05:18:58 PM · #11
You can make an analogy between cars and cameras. Pixel count would be like engine horsepower--an important number, but it doesn't tell you much. A dump truck may have the same horsepower as a sports car, but they're not the same. Just as torque is another important number for engines, dynamic range and sensitivity (ISO performance) are important to sensors. Then, in both cars and cameras, the body and other mechanical systems will make a big difference.

Message edited by author 2007-01-13 17:19:54.
 01/15/2007 09:24:57 PM · #12
You'll also pay dearly for a fully sealed camera! Plus, the d200 has much more "thoughtful" features.
 01/15/2007 10:05:17 PM · #13
there are more to a camera (body) than just the sensor.
i'm sure someone before me would have already pointed that out in details.
as an example, even when 2 computers have the exact same processor, their speed and performance will still differ, and that's also why the price differs.
 01/22/2007 01:47:06 AM · #14
Originally posted by jlfarrell:
If that is true, then what about Nikon's flagship camera the D2X? It has the same exact size sensor, but has a higher 12mp resolution. That means it has smaller pixels, spaced closer together. So, question 2 - Does that mean that the image quality of the Nikon D2X would be less than the Nikon D200 or Sony Alpha?

And finally, if the above two questions are true, then what is the advantage of buying a more expensive camera if the image quality is the same? How much impact does the lens quality play in the quality of the image?


Hmm, lots of stuff to address here, as people have already pointed out, the sensor in your camera, and the one in the D200 are not the same at all, 2 channels vs. 4 channels, different number of total pixels, different manufacturer serial number and so on. On the other hand, they are both CCDs, the sensor in the D2X on the other hand is a CMOS sensor, which gives it a few other advantages, besides the added pixels and 4 channel readout.

CMOS sensors consume less power than CCD sensors, an advantage that increases as sensor size increases. Also, the signal in a CMOS sensor is read at each pixel, rather than in a bucket relay, horizontally and vertically across the whole chip, as in a CCD. This is what allows the D2X to use only part of the sensor for it's high speed crop mode.

Another advantage of CMOS is that on-chip noise reduction circuits are possible , allowing noise to be removed before the signal is transmitted to the image processor. With a CCD the noise reduction can only be performed by the image processor itself.

Alright, so your question was whether or not the D2X will have poorer image quality than the Sony Alpha or D200. Yes, it has smaller pixels than some other digital SLRs, and larger pixels are an advantage to an extent, especially when talking about compact digitals with tiny sensors. Larger pixels can offer greater dynamic range, as well as less visual noise, and therefore do not require the same level of signal boosting and noise reduction as smaller pixels at high ISO. Case in point, Everything above ISO 800 on the D2X is "boosted".

On the other hand, when it comes to actual resolving power, more pixels, closer together are better, but don't take my word for it. This test compared the actuall line per picture height resolution of the Canon 20D, Nikon D200, Canon 5D, and Nikon D2X, all with equivalent glass. Now all the other cameras in the test have larger pixels, but the D2X displays more resolving power than any of them //www.dpreview.com/reviews/nikond200/page30.asp

Moving on... why buy a more expensive camera if the image quality is the same? Well, for one thing, you're not just paying for a sensor, you're paying for the whole camera, it's materials, build quality, features, mechanical performance specs such as shutter speed and shutter life, and in turn, the lens system and other accessories that the camera body supports. Not to mention, even with the same sensor, one image processor may get more out of it than another. If I were buying a new digital SLR (which I am in the near future), here are some features that I would pay extra for: A weather sealed metal body, Large buffer, high continuous frame rate, longer than average tested shutter life, large, bright viewfinder, intelligent TTL light metering, wide range of in image quality options, and adjustments, long battery life, superior overall feel and control layout, support for a wide range of top quality lenses.

Alright, you get the idea, and that also brings me to your next question: "How much impact does the lens quality play in the quality of the image?". The short answer is, more impact than anything else you can think of. I forget where I first saw this quote, but it's worth repeating "The camera is just a box you put your lenses on". Something to that effect, it was referring to film SLRs, where it's even more true, since the box isn't limited to one image sensor, but gets a new one with every frame you take. It still holds true though. All you have to do is take the lens off your camera and look through the viewfinder, even take a picture if you want, to see how important the lens is to image quality. Personally I have no experience with Sony lenses, what I do know is that Nikon has been making camera lenses for over 70 years, Canon (I'm currently a Canon user) and Pentax have been doing so for nearly as long, Sony has not.

There's my two cents, hope it was helpful.
 01/22/2007 02:05:59 AM · #15
something to ponder about regarding pixel density and resolving power?
01/22/2007 02:11:18 AM · #16
Sony A100
Nikon D80
Pentax k10D
Samsung GX10

I believe are the dSLR cameras that uses the same or very similar sensors.

Message edited by author 2007-01-22 02:11:35.
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