Reasons for wanting higher mega pixel count

Started 3 months ago | Discussions thread
Scottelly
Scottelly Forum Pro • Posts: 13,641
Re: Not my experience.
2

Jacques Cornell wrote:

canonpfs wrote:

Much is said about the Sony A7R IV's "too high" mega pixel count. It seems the only reason that people can think of for needing a high mega pixel count is cropping. Besides cropping, here are two additional reasons for wanting more mega pixels:

1. Sharper images. Have you ever looked at an image on your rear LCD and thought that they were sharp only to find them blurry on your home monitor? Yes, I know we should look at our images on the LCD at higher magnifications but please bear with me for a moment. The reason why the blurry images looked sharp on the LCD is because a large image is displayed very small. So you shoot in low light and there is a breeze. You are already at a high ISO to get a higher shutter speed but the flowers in the foreground are still slightly out of focus. With lots of mega pixels available this image can be down sampled. At a smaller size the flowers are now sharp. Taking an image from 61MP down to say 18MP sharpens slightly out of focus areas.

Once you get beyond the minimum ppi (about 200-300) required for output at a certain size, additional pixels are wasted. A postcard printed from a 6MP file looks no less sharp than one from a 42MP file.

That's true, but to get the same quality print at twice the height and width, you can't use that 6 MP file. Instead you have to use a 24 MP file, and that's just for an 8x10. What if you want to print at 16x20? You guessed it, you need four times as many pixels as the 24 MP camera captures, so the 42 MP file just won't do the job. 16x20 is not really common, but there are plenty of people who have a portrait that size. My mom got a portrait of her kids made on medium format film when I was a kid. She got it printed at 40" x 60" (yeah, that's 5 feet across). Luckily there's a couch in the way, so people don't step right up to it, because the image quality just isn't that good. It looks grainy and a bit blurry. Maybe it just wasn't scanned at a high enough resolution. It's getting pretty old now though, so who knows the reason it doesn't look better?

I'm happy Sony decided to unfetter people who want to make big prints or crop a lot. Sure, there are plenty of people who are happy with their 12 MP or 24 MP camera, and they can keep buying those, but for people like me, who dream of a future with ten foot wide 8K screens everywhere, who want the highest resolution possible, Sony has done the right thing. I congratulate them and all the people who will buy the Sony A7r IV.

2. Lower noise. Provided the 61MP sensor provides the same high ISO performance as the 42MP sensor the larger sensor will result in lower noise when down sampled. Noise just seems to magically disappear with down sampling. So if you have noise in the 61MP image just down sample it and the perceptible noise will be less.

Downsample a 42MP a7RII image to 12MP and compare the result to a 12MP a7SII image at the same output size and you will see almost identical noise. More pixels do not reduce noise. Likewise, reducing the number of pixels does not reduce noise. This is because with modern sensor designs, noise is a function of the physical size of the lens aperture (and thus total light collected) regardless of pixel count or sensor size.

3. Higher usable ISO. For the same reason as mentioned above the higher mega pixel count allows you to use a higher ISO because the additional noise generated by the higher ISO will be cancelled out by down sampling the image (within reason of course).

See my response to number 2 above. I get the same usable max ISO from my 24MP a7III and my 42MP a7RIII.

So call me crazy if you please but I am very pleased with the higher mega pixel count. It has its uses other than just cropping.

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Scott Barton Kennelly
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