I have elements but haven
I have elements but haven
Denise,
I think the difference in high ISO performance between cameras can be atrributed to a large part on pixel size.
The 7D having 18 megapixels on a 1.6 crop factor sensor has much smaller pixels than a 40D which has 10 megapixels on the same size sensor. Think of 18 small buckets on your front porch in the rain versus 10 bigger buckets....the smaller buckets catch less rain drops each.
Thus.... the smaller pixel is able to collect a smaller number of photons...so ech pixel will have a lower signal to noise ratio.....now to increase ISO the camera amplifies electronically what it is receivng from the sensor and so the noise becomes even more evident.
The smaller pixels though will collect more detail.... so if you shoot a bird picture you will have more pixels on the subject and with proper exposure, you can get more detail and you can maybe get away with a larger crop of your images without losing image quality. This (and the fast frame rate and video) is the strong point of the 7D.....it is well known not to be a great high ISO performer. In the Canon line the 5D MKII and the 1D series are the best at high ISO. Also it is well known that the upper end Nikons are better high ISO performers than Canon.....especially the D700 and D3s.
It
Originally Posted by Joel Eade
Daniel may chine in here, but I'm pretty sure this hypothesis has been debunked and the size of the pixels does notdirectly affect ISO noise. What does affect ISO noise is the size of the sensor - in other words, it's the total light gathered that determines noise, and total light is directly proportional to sensor size. That's the main determinant, with secondary differences resulting from the quantum efficiency of the sensor's pixels, in-chip processing, etc.
I did a quick empirical test of that myself - comparing images from two P&S cameras, a Canon S95 and an Olympus C-765UZ. The S95 is 10 megapixels in a 1/1.7" sensor, so the pixel density is 23MP/cm², and the Olympus is 4 megapixels in a 1/2.5" sensor, and thus has a lower pixel density of 16MP/cm². So, the S95 has an 80% larger sensor than the Olympus, but the Olympus has 44% larger pixels than the S95. If larger pixels mean less noise, the Olympus should have lower noise, and if a larger sensor means less noise, the S95 should have less noise. Comparing at the same ISO, the S95 is the clear winner with noticeably less noise.
You would see the same thing if you compared noise across two dSLR sensors with the same pixel density, e.g. the 5DII and the 20D (both with 2.4MP/cm²- the 5DII will have significantly lower noise at a given ISO, even though the pixels are the same size.
So, the smaller pixels of the 7D mean higher resolution than the 5DII, whereas the larger sensor of the 5DII means less noise than the 7D.
I think the big argument was that it doesn't increase the noise of the picture overall. If you were to resize your 18MP 7D image to 10MP, you'd get an image with the same noise as you would from a 10MP sensor. At a 100% view of the 18MP image, you will see more noise per pixel. There are also some finer picture details along with the noise. If you're feeling you would have been better off with a 40D 10MP sensor, simply resize your 18MP image to 10MP and you'll have the same noise level, and perhaps some extra edge smoothness due to the extra detail also picked up by the higher res sensor.
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R8 | R7 | 7DII | 10-18mm STM | 24-70mm f/4L | Sigma 35mm f/1.4 | 50mm f/1.8 | 85mm f/1.8 | 70-300mm f/4-5.6L | RF 100-500mm f/4-5-7.1L
Here is what I had previously read about pixel size.....I don
Great posts, everyone.
Roger Clark is pretty brilliant, but there are several things he gets wrong. In a lot of places he mixes up the difference between pixel size and sensor size (claiming that large pixel sensors are better in circumstances when it's only better because the entire sensor is larger). In other places he compares sensor performance at completely different spatial frequencies without accounting for scale. It's like comparing road noise for at 50 MPH in one car and 100 MPH in another car -- you have to compare them both at the same speed to really find out which one has more noise.
Nice read - thanks! I don't think the conclusions are mutually incompatible, but if you buy into the author's model of an 'apparent image quality' (AIQ) and look at how he's plotted that, it seems that while both pixel size and sensor size affect that value, sensor size has a much bigger relative contribution to the metric. Until he gets to the section on "Different Sized Pixels in the Same Sized Sensor," he's basing all of his comparisons on the S70 (0.38 cm² sensor) vs. the 1DII (APS-H, 5.48cm² sensor) - the latter has a 3.6-fold larger pixel pitch (linear dimension), but also a 4-fold larger sensor (linear dimension). Looking at his AIQ plot, a full-frame sensor surpasses the best possible performance of any APS-C sensor, regardless of pixel pitch.
We can all agree that the dSLR will perform better, but since both pixel and sensor size are much larger, that doesn't address the relative contributions of the two, and the author does nothing to distinguish them (which seems to bias the conclusions).
So, if you're comparing sensors of the same size but different pixel densities (e.g. 50D vs. 7D), the larger pixels should be better in terms of ISO noise, i.e. the 50D should 'win' - and by some of the metrics in the article it does. But by other metrics and real-world performance tests (e.g. Bryan's reviews), the 7D is actually a little better than the 50D - as Bryan states, "As sensor density increases, so too does high ISO noise -unless improvements in the sensor and subsequent image processing are made." Likewise, if you're comparing sensors of different sizes, the larger sensor will perform better in terms of ISO noise. But I think the sensor size effects trump the pixel size effects
Guess that
MF cameras have better ISO performance than FF dSLRs, yes. The two highest-scoring sensors on that AIQ plot are the KAF-18000CE and the KAF-31600, and those are Kodak ~46x35mm sensors used in medium format cameras. So, both are higher than any FF sensor, with only the peak theoretical FF AIQ near the level of the 18 MP MF sensor. The 32 MP MF sensor is the clear winner in this metric.
So, looking at that overall trend and the theoretical curves for f/8 diffraction limit, it appears that sensor size defines groups within the AIQ range. For all non-P&S sensors, existing models fall in a range of ~4-9 µm pixel pitch. Within that range in terms of AIQ scores, the theoretical and measured sensors perform as follows:
- 1.6x sensor - AIQ of 40-55
- 1.3x sensor - AIQ of 55-80
- FF sensor - AIQ of 75-130
- MF sensor - AIQ of 120-170
Those group are almost non-overlapping, indicating that pixel size impacts AIQ primarily within a group defined by sensor size. That's consistent with sensor size being the key determinant of performance - it implies no matter how optimal your pixel size is for a given sensor size, the best you can do is to almost equal the least optimal pixel size in the next incrementally larger sensor. Put simply, sensor performance scales primarily (but not exclusively) with sensor size, less so with pixel size.
Looking at the DxOMark sensor scores, I wonder how Nikon cameras would fit into the AIQ plot...
Here iwww.dxomark.com/.../579|0/(appareil2)/436|0/(appareil3)/628|0/(onglet)/0/(brand)/Phase%20One/(brand2)/Canon/(brand3)/Nikons what I was searching for.......
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