Reasons for wanting higher mega pixel count

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canonpfs Junior Member • Posts: 36
Reasons for wanting higher mega pixel count
9

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.

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.

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).

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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JimKasson
JimKasson Forum Pro • Posts: 26,689
Re: Reasons for wanting higher mega pixel count
8

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.

That is true, but it's a second order effect if the CoC of the blurry flowers is much bigger than the pixel pitch. It occurs because the sharpening algorithms work better with more samples. By the time the CoC gets to 4 or 5 pixel pitches, the improvement is virtually gone.

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.

This is true if you use nonlinear noise reduction. If you use linear noise reduction, it's pretty close to a wash, since the full well capacity for a given sensor technology is mainly proportional to the area of the pixel.

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).

Again, only true if you use nonlinear noise reduction.

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.

It has advantages that you haven't mentioned: less false color, less aliasing, sharper images in general.

Jim

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mcrksman Contributing Member • Posts: 522
More cropping power too
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dv312
dv312 Veteran Member • Posts: 8,645
My only reason
7

Cropping, cropping, and more cropping

Ultra necessary for birding

Everything else is just icing on the cake

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KE_DP
KE_DP Veteran Member • Posts: 5,627
Re: Reasons for wanting higher mega pixel count
7

Another huge reason - pixel level editing and/or retouching.  Maybe a lot of people don't do this, but it's a huge difference from 24 to 43 - so 61 will be most excellent to work with.

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Jacques Cornell
Jacques Cornell Forum Pro • Posts: 11,623
Not my experience.

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.

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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JimKasson
JimKasson Forum Pro • Posts: 26,689
Re: My only reason
2

dv312 wrote:

Cropping, cropping, and more cropping

Ultra necessary for birding

Everything else is just icing on the cake

I'm not a birder, but if I crop by more than a little bit in both directions, I consider the exposure imperfectly designed.

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Horshack Veteran Member • Posts: 8,017
Re: Reasons for wanting higher mega pixel count
2

canonpfs wrote:

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.

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).

This is a oft-quoted theory but is incorrect when you think through it more deeply. The only situation where extra pixels yields can yield better High ISO results in terms of noise and detail (ie, the ability to apply more NR to the higher-resolution image to yield better downsampled results vs an image from a lower-resolution sensor) is when you compare the two using locked-down tripod shots, at identical shutter speeds. In other words, only in an artificial comparison that never can happen in the real world.

The reason it can't happen in the real world is because High ISO is used when you're either shutter speed or DOF/aperture limited. For example, to get a fast enough shutter speed to avoid motion blur from a moving subject or shake blur from hand-holding a camera , or when you need to step down the aperture to get sufficient DOF. In both scenarios if there isn't enough available light to accommodate that faster shutter speed and/or smaller aperture then one must increase ISO in order to maintain the same pixel-level sharpness desired (ie, absence of undesirable blur).

As the pixel density increases one must increase the shutter speed a commensurate amount in order to maintain the same pixel-level sharpness. Pixel-level sharpness is necessary in order to take advantage of the detail advantage from downsampling a higher MP image to achieve better post-NR detail results vs a lower-resolution sensor. Otherwise the higher MP image will just be oversampling motion blur, yielding no detail benefit when downsampled.

Since a higher shutter speed is necessary for a higher MP sensor to achieve the same amount of pixel-level sharpness, the ISO must be increased on the higher MP sensor vs a lower MP sensor. And with that the presumed detail+noise advantage from a higher MP sensor suddenly disappears...because the amount of ISO increase necessary to keep per-pixel sharpness scales directly with pixel density.

As indicated, the only situation where you don't lose the presumed Higher MP advantage is in artificial test scenarios, where you lock both the higher MP and lower MP cameras on a tripod shooting a static, non-moving subject and with both cameras set to identical shutter speeds. In the real world you can't do this because, again, the only reason to use Higher ISO is to avoid blur, so if you have the ability to avoid blur at any shutter speed on a tripod then you would necessarily be using a lower ISO to begin with.

joger
joger Veteran Member • Posts: 5,658
Re: Reasons for wanting higher mega pixel count
5

unfortunately these discussions are utterly useless.

You'll find two types of people participating:

One group will tell you that its stupid to "waste" pixel you'll never going to see - I have a problem with the framing "wasting" to begin with.

You're oversampling not throwing away pixels - they get used not wasted.

Another group is telling that more is always better without thinking twice what those pixels could do for us.

Truth is that too small pixels might have effects from shrinking the individual pixel and thus can be lower in image quality. There was some years ago a Nokia image sensor with 40 Megapixel in a smartphone camera - this camera only worked acceptable in super bright sunlight since the pixels were too small for the slightest raise in ISO.

With the new A7R IV Sony states that the pixel efficiency was upped to the same level or even above the pixel level of the A7R III due to the better BSI signal conversion plus the new AD conversion. Let's cross fingers this is true.

Noise from sensors with the same generation of signal processing will be similarly noisy in the output result as long as the enlargement doesn't exceed your resolution of your eye.

So yes - an A6 sized print will always look fine - you need maximum 4 MP to exceed the resolution of the human eye with your nose sticking to the postcard.

( Fortunately most of us don't have to earn their money with post card photography )

The two groups argue with good arguments until none of the two is happy at the end.

Truth is that there are many reasons for more 'good' pixels.

  • cropping
  • oversampling
  • image corrections on pixel level
  • pixel level editing

It looks like Sony has upped the pixel level signal : noise ratio quite a bit and thus we should see at the same output size a better image quality compare to the A7R III. The A7R III was already better than the A7R II and better than the A7R.

This will not continue forever. There will be limits in efficiency and to my best knowledge we are in some areas reaching that. Jim has sure some measures for that.

I'd not expect that Sony will bring ongoing more pixels for the "R" models. At some point this will end. My guessing is 70..80 MP for FF might be a natural end and trade off between pixel size and possible efficiency. Maybe the sensor makers have some tricks here and there.

But there will be an end.

The current almost 61 MP pixel count seems to work great for Sony and the initial images published look stunning to say the least.

The 'meh' and 'no' sayers forget that we see advantages - the proof is in the pudding.

The discussion will have - unfortunately - never an effect since both phenotype groups will never admit that the other one is right ignoring the grey area between them.

This is a social behavior we see in the western world in many formerly civilized and grown up perceived countries.

I am very sad about that.

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Gerald Brooks Regular Member • Posts: 215
Re: Reasons for wanting higher mega pixel count
15

Reminds me of when I heard an old guy say that there are two things old guys don't like -- change and the way things are.

Batdude
Batdude Senior Member • Posts: 4,110
Re: My only reason

dv312 wrote:

Cropping, cropping, and more cropping

Ultra necessary for birding

Everything else is just icing on the cake

Just curious, I am not a BIF photographer and own zero zoom lenses and the longest FL I have used was the Sigma 150-600 at the camera store parking lot. From my own personal experience and the very little I have used long lenses what I understand is that it is not easy to photograph moving objects with long lenses, but the point is this, don't you have to be extreme careful as to how you shoot anything that is moving specially with higher MP cameras?

Doesn't it get worse as you increase MP? When you crop, and crop and crop (or in general) isn't there more blurr if one doesn't know what they are doing? You make things sound very simple

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joger
joger Veteran Member • Posts: 5,658
Re: Reasons for wanting higher mega pixel count
3

Gerald Brooks wrote:

Reminds me of when I heard an old guy say that there are two things old guys don't like -- change and the way things are.

a good one !!

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LoneTree1 Senior Member • Posts: 1,567
Re: Reasons for wanting higher mega pixel count

Because it's there.

mcrksman Contributing Member • Posts: 522
Re: My only reason
13

JimKasson wrote:

dv312 wrote:

Cropping, cropping, and more cropping

Ultra necessary for birding

Everything else is just icing on the cake

I'm not a birder, but if I crop by more than a little bit in both directions, I consider the exposure imperfectly designed.

Its hard to avoid cropping when birding. Most of the time the birds are too far away which might be fine on rare occasions depending on the surroundings, and also by the time you adjust everything for the perfect composition you're gonna be shooting plain tree branches with no bird

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Paul Barnard
Paul Barnard Veteran Member • Posts: 3,167
perspective correction
2

more pixels is good for this.

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Paul Barnard
Paul Barnard Veteran Member • Posts: 3,167
Re: Reasons for wanting higher mega pixel count

KE_DP wrote:

Another huge reason - pixel level editing and/or retouching. Maybe a lot of people don't do this, but it's a huge difference from 24 to 43 - so 61 will be most excellent to work with.

Masochist...

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Corelli Veteran Member • Posts: 3,749
Re: perspective correction

Very good point for those of us who shoot interiors and exteriors of cathedrals and other architecture.

Cheers

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ClementPhotos Regular Member • Posts: 249
Re: My only reason
4

dv312 wrote:

Cropping, cropping, and more cropping

Ultra necessary for birding

This is about the only reason I need to put a7R IV on my shopping list.

a7R IV + 200-600! You can't get away from me now, birds! (well, in the near future lol)

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lovehifi Contributing Member • Posts: 581
Re: My only reason
1

Same here. Mostly for birds and wildlife. Plus I like having a 26 megapixel crop mode when I want it. 18 megapixel is pretty good on my Mk3 but 26 is better.

Trollmannx Senior Member • Posts: 5,675
Re: Reasons for wanting higher mega pixel count
1

More pixels means more control over in camera lens correction (and that is what Sony has stated). Leave optical correction to what lenses do better and leave other aberrations to computers and we get the best of both world.

Advantages when the lens outresolves the image sensor:

More pixels also mean more resolution with a shorter focal lenght. The 24 MP 135 mm image will have similar resolution as the 61 MP 85 mm image and the latter show similar detail and has a much larger field of view.

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