Selection of Full Frame or Crop .... based on ISO performance.

This is serious stuff guys ..... when ever i hear or read that ..... "We need full frame for better ISO performance" ...... and i was like 😳  & 😁 at the same time. 

If you talking about bad ISO of a crop body and have a strong believe that only full frame gives better performance ...... then let me know why Canon 5DS/5DSR which is a full frame body ..... Why it is starts producing noise even at low ISO like 400? Why it is max out at ISO 3200/6400?

And the answer is ..... Pixel Pitch (Pixel Width) ..... Higher Mega Pixel make smaller size pixels which cannot provide sufficient gain over time (G/T) to have better ISO & sufficient Dynamic Range. The pixel width & depth is not enough to hold more light & they get saturate earlier then expected. 

The new trend by all these camera manufacturing companies is to make a full frame camera bodies with crop body pixel pitch. It means, they are having the same old crop body who's sensor is over 24x16mm size with specific pixel density, they uses the same pixel density of a crop sensor and overlay it over 36x24mm sensor and makes a new breed of Mega Pixel Monsters.

Let me explain with examples here. It was started with Nikon D7000. Nikon used 16MP sensor of D7000 which was spread over 24x16mm, and then spread the same pixel pitch (pixels per square millimetre) over 36x24mm sensor and made the world first Mega Pixel Star ...... Nikon D800/D800E.

This trend was later followed by Canon. They took their 7D MkII which was 20MP machine and enlarged it pixel pitch over full frame and introduced you the world first 50MP machine 5DS/5DSR. But if you look at the ISO performance of the D800 or 5DS, their performance at higher ISO is exactly like D7000 & 7D mkII respectively ..... because they are made on the foundation of a crop body sensor pixel density. Which leads to this interesting fact that the "Gap of Performance" between Full Frame & Crop Body is almost gone. Now both are more or less the same ..... specially if you talking about higher Mega Pixel machines. Now i am waiting for the Nikon reply for the  Canon 5DS/5DSR. If they uses Nikon D500 and enlarge it sensor over full frame area then we might have 47MP machine ..... or if they uses the D7200 for the same purpose then we will have 54MP monster under the name of D850/D900.

Below are some old camera in comparison. You can plot the new higher MP machines into this chart and then you will see some interesting co-relation. 

If you look closely above, you will notice Nikon D3200, D600 & D3x all are having same mega pixels. But Their pixel size is different. D3200 having 4um & D600/D3x haivng 6um. Reason is simple, D3200 is crop size sensor body so area of the sensor is small but there are more in quantity so the effective pixel size has to be smaller unlike D600/D3x which are full frame sensor cameras where the sensor size is bigger. 

Another interesting fact if you notice is that all camera in the above list and the new ones, their pixel size is not smaller then 4um. Reason is that all these camera companies found out that 4um is the threshold of a pixel pitch where they can have maximum efficiency physically from a silicon wafer of sensor which can provide sufficient Dynamic Range and optimum ISO performance. (Note: 4um means around 24MP). Therefore you cannot see from Nikon or Canon or Sony or Fuji manufacturing any crop body or full frame with pixel pitch smaller then 4um...... in other words they are not making crop body more then 24MP. You may found some machine like 3.9/3.8 but they are floating around 4um. Any camera with less then 4um pixel pitch produces worse Dynamic Range. The best examples are the mobile phone cameras where the pixel pitch is around 1~1.5 micrometer and their performance is not even close to the DSLR. But due to better SNR firmware they are doing some really decent job.

Please see below the Dynamic Range chart containing both full frame and crop sensor which will help you in understanding the relation between Mega Pixels & Dynamic Range. 

Here is another funny thing ..... it doesn't matter what format of camera you are using ..... exposure of any scene always remains the same on all type of camera sensors, it never changes, which means ISO is totally irrelevant then. What matters are the following things,

- Aperture of the lens 

- Shutter Speed 

- Pixel pitch (also known as Mega pixels)

All these 3 items mentioned above in general knows as "Native Gain". By adding or subtracting any of above 3 things.... you can have better or worse results. For example a kit lens with Aperture f/3.5~5.6 not enough to provide better native gain unlike a prime lens of f/1.4. Same goes slower shutter speed where you can drag the shutter slow and get more light into the sensor by keeping lower ISO.

Let me share some more example to make better understanding about Pixel Pitch. Nikon D3/D3s/D700 & Sony A7S/A7SII all are 12MP which means they all are having 8.4um pixel pitch which is exactly double then Canon 5DS/5DSR 4.14um. This means that all machines of Nikon & Sony can handle low light situation pretty darn well because their sensor got "bigger" eye balls then Canon. They have the tendency of capturing light more then double & still produces low noise in compared to Canon 5DS/5SDR ...... and funny thing is that they all are Full Frame but still 3 performs better then 1 ..... All because of different pixels sizes and its impact.  

Now some one will jump and say "What about ISO?" ..... i mentioned this thing multiple times in past that ISO is just a "Applied Gain". The way you increase the audio in a stereo system, ISO exactly works in the same way. You can change the applied gain in post processing but you cannot change the "Native Gain" change in post processing ..... thats why they are Native.

Bottom line is ..... This impression that Full Frame works better in low light & produces less noise ..... i just explained in detail above with example that it is not the case any more. The difference of performance between the full frame camera body & crop sensor camera body is now near to ZERO. Todays crop body DSLR are performing far better then full frame of the past. Best example is Nikon D500 which is giving you the latitude of ISO performance upto 51,200 ISO which was unheard 10 years ago. Not even Full Frame released 8~10 years ago can go upto this much ISO .... thanks to the new sensor technology, advance A/D convertor & SNR firmware which all these camera companies working very hard on and releasing product to make our life easy.

But our life is never bin easy because we are engaging in this machine/brand rivalry instead of focusing on developing our skill set of Photography.

Happy Learning Guys 👍🏼

Babar-Photography 

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Reference:
http://www.clarkvision.com/articles/digital.sensor.performance.summary/