Sony's 24mp for high iso

Started Jun 10, 2012 | Discussions thread
Robsphoto Senior Member • Posts: 1,219
Re: Big pixels gather more light than small pixels

TrojMacReady wrote:

Robsphoto wrote:

theswede wrote:

Robsphoto wrote:

If you want the best low light performance possible, which camera would you choose?

The one with the largest sensor. Pixel pitch is not a factor as long as the sensor has enough resolution for my needs.

Ok, let's assume that you want to pick between two full frame cameras, both of which have the SAME sensor size of 36mm x 24mm.

The two choices are:

12mp Nikon D3S, which has a pixel pitch of 8.5 microns

36mp Nikon D800, which has a pixel pitch of 4.9 microns

It should come as no surprise that, for quite a long time, the Nikon D3S has been regarded as the best low light camera on the market.

Do you think it's just a coincidence that the Nikon D3S has a pixel pitch that is larger than any other full frame camera, and therefore has probably been better suited to low light photography than full frame cameras with smaller pixels?

It was designed to be best and it remains unbeaten, mostly because we've been hitting a barrier in quantum effieciency. Others have pretty much equaled it for a given output size, such as the D4. And the D800 is within a hair, while having pixels that much smaller. But what's more telling is that sensors with pixels several times smaller, are sitting at the same efficiency level too.

Think V1/J1, FZ150, G11, G12 etc. Pixels as small as 2 micron and smaller. The key is comparing sensors per similar area, not per pixel. The same goes for output. Sensor size is what mostly matters.

If people do a reasonably conscientious internet search, they will find a lot of material that confirms what could be regarded as a “general rule” about the role of small pixels and large pixels, as nicely set out by Bob Atkins:

" So what you get with sensors is a tradeoff of resolution for noise (and the related dynamic range). Big pixels give you lower resolution, lower noise and higher dynamic range. Small pixels give you higher resolution, higher noise and lower dynamic range. The real question is what constitutes "High Enough" resolution and "Low Enough" noise. Can you have both? "

The “Cambridge in Colour” tutorials are very good, and although they acknowledge that the amount of background noise also depends on the sensor manufacturing process, they nevertheless seem to support the “general rule” as stated by Bob Atkins.

Larger pixels receive a greater flux of photons during a given exposure time (at the same f-stop), so their light signal is much stronger. For a given amount of background noise, this produces a higher signal to noise ratio — and thus a smoother looking photo. This is not always the case however, because the amount of background noise also depends on sensor manufacturing process and how efficiently the camera extracts tonal information from each pixel (without introducing additional noise). In general though, the above trend holds true.

In some recent postings to the Bird Photographers forum, Roger Clark produces some very interesting practical comparisons of cameras with pixel pitches of 4.3, 5.7, and 6.4 microns. It’s no surprise that he concluded that the 6.4 micron pixel images have the highest signal-to-noise ratio, but the least detail. Again, this seems to conform with the “general rule” stated above.

I have found one article which supports the view that the “light collection efficiency per unit area is essentially independent of pixel size”. This view is advocated by Emil Martinec:

I suspect this paper has had a strong influence on people who are advocating this view in this forum!

However, if someone was doing a literature review for a University paper and relied mainly on what can be found on internet, they could be forgiven for concluding that large pixels do in fact play a very important role in reducing noise, just as small pixels are much better than large pixels in resolving fine detail.


Comparison of pixel size, pixel density etc. of a 36mp FF camera (e.g. Nikon D800) with a 24mp APS-C camera (e.g. Sony A77)

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