Nikon Z 24-200 f/4-6.3 compared to Canon RF 70-200 f/4

Started 8 months ago | Discussions thread
(unknown member) Regular Member • Posts: 394
Re: R5 has AA filter and Z7II does not...
1

kenw wrote:

Travis Nicky Bombastus wrote:

Could someone explain what a "lower fill factor" for the Nikon Z7 II sensor means?

Fill factor means how big the light gathering area of the pixel is relative to the pixel pitch (spacing).

A sensor with a fill factor of 100% would have its whole surface gathering light - the photosensitive areas of adjacent pixels (the photodiodes) would be just touching. In reality this isn’t possible as there needs to be area around the pixel photodiode for electronics (transistors for reading and reset). Micro lenses on top of the pixels effectively increase the fill factor by focusing light that would have hit those electronics onto the photodiode. Backside illuminated designs (BSI) move those pesky transistors to the other side of the sensor so the photodiodes can be bigger.

What this means for MTF or if you want “sharpness” is that while a higher fill factor means gathering more light it actually results in a slight reduction in MTF compared to a lower fill factor. This is counterintuitive and needs a bit of math to explain which I won’t attempt to cover here (but if interested there are some good explanations online).

Usually sensor designers are worried about noise and sensitivity and thus opt to make the fill factor as close to 100%. Thus usually one say 50MP FF sensor will act pretty much like any other (assuming no AA filter) in system MTF tests like these. But in certain cases the camera designers have intentionally reduced the fill factor to get “sharper” images at the cost of somewhat reduced sensitivity and high ISO performance.

Clear as mud?

Ken, thanks...really appreciate this and your original post.  I first saw this "fill factor" phrase mentioned in the context of DPR's GFX 50 II review, and when I saw it again in your post, I finally had to ask what it meant.

Your explanation helps clear things up.

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