Is the extra resolution really worth it?

[jtunney]

Pardon my ignorance, but I have a few questions. DXOmark's mpix ratings have generated several discussions because they seem to show that most lenses don't match the resolution of high megapixel cameras like the D810. There are a couple of threads out there that address the issue, but they tend to get very technical without getting to the punchline (or maybe it just went over my head).

So here are a few direct questions:

A 36mp camera will produce 50% greater resolution than a 24mp camera even if the lens resolution on both cameras maxes out at 22mp - correct?

If so, will it make a noticeable difference on a 16x20 print?

Thanks.

[ErikKaffehr]

Hi,

Answers below:

So here are a few direct questions:

A 36mp camera will produce 50% greater resolution than a 24mp camera even if the lens resolution on both cameras maxes out at 22mp - correct?
Answer: not correct.

If so, will it make a noticeable difference on a 16x20 print?
Answer: no it won't

Explanation:

• Almost any lens will outresolve any sensor at centrum at optimum aperture
• Errors multiply, so a low resolution sensor will degrade a low resolution lens as much as a high resolution lens
• Hi resolution lens with a low resolution sensor will yield artefacts
• Hi resolution essentially comes free, the price may be a minor reduction of DR

On the other hand:

A low resolution sensor with a high resolution will yield fake detail. But, fake detail is hard to tell from real detail.

Another side of the same coin is that it seems that something like 180 PPI is needed for a very good print. So, once you are beyond 180 PPI, it will be hard to see any objective difference between two prints, if viewed at 50 cm with normal vision.

But, human vision is extra sensitive to broken lines, for instance. So, you would be able to observe a difference on line patterns on prints that are beyond the 180 PPI limit on fine detail, like test charts or bank notes.

To put it short. Reproduction quality is a product of all degradations in the imaging chain. Any improvement in any part of the chain will result in an improvement. With low resolution sensors and high resolution lenses image artefacts will result. But, all this may not be visible in small prints, except on test charts.

Personally, I don't think I see a difference between 24 MP full frame and 39 MP MF at A2 size. Printing larger the difference starts to be noticable. That is with my vision, your mileage may vary…

On the other hand, an expert printer stated that there is an obvious advantage to 36MP prints over 16 MP prints at A2 size, at least on glossy paper, viewed side by side.

Another way to see it is that a high resolution sensor will improve all your images, while going from a decent lens to an excellent lens may not improve the images that much if you shoot around f/8.

So the issue is complex, more pixels are essentially always beneficial, except at very high ISOs, but if you see that benefit is a different question.

Best regards
Erik

[Paul2660]

Not on a 16 x 20 print at 360 dpi, on an Epson printer or 300 dpi on a Canon.  It will make a big difference on a 30 x 40 or 40 x 60 on both of these printers.  To get to 40 x 60 both camera files you mention will still need uprezing to get to 360 or 300 dpi for the printer and you don't want the Epson driver to do it (can't speak to Canon's). 

For the web, it will never really matter as the web runs at 72 dpi and the sRGB colorspace for the vast majority of users and I don't see that changing anytime soon.

Paul

[Rhossydd]

For the web, it will never really matter as the web runs at 72 dpi

The 'web' doesn't have resolution, it's just a delivery mechanism.
72dpi is a very old concept of the average monitor pitch that's well out of date now.

[Paul2660]

The 'web' doesn't have resolution, it's just a delivery mechanism.
72dpi is a very old concept of the average monitor pitch that's well out of date now.

I realize this but most images out there are 72 dpi based and the average viewer does not have the capacity to appreciate anything else.  As the vast majority are taken from camera phones and most of these are taken in this format.   I don't feel it's out of date either as most programs with a Save to the web option default to 72 dpi also and most browsers still seem to prefer it.

Paul

[E.J. Peiker]

Incorrect, you can post a photo of the same x by y pixel dimensions at 1 DPI, 72 DPI, 1,000,000 DPI or any DPI you want.  The internet will display it exactly the same way on a given monitor.  It displays one pixel per pixel and completely ignores any DPI information.  DPI or PPI matters when printing but not on the Internet.

[Paul2660]

Incorrect, you can post a photo of the same x by y pixel dimensions at 1 DPI, 72 DPI, 1,000,000 DPI or any DPI you want.  The internet will display it exactly the same way on a given monitor.  It displays one pixel per pixel and completely ignores any DPI information.  DPI or PPI matters when printing but not on the Internet.

Thanks for the correction. I will keep on with 72 for my web work. Seems to work just fine for me. I think you would have some trouble uploading a 1 million dpi image even if it would be displayed the same. Maybe not.

Paul

[E.J. Peiker]

No you wouldn't have any problem uploading it, the upload time would be identical - the DPI doesn't matter, it's only the actual pixel dimensions.

Lets say you upload a 1000x667 pixel image. It displays on your monitor, after upload, at 1000x667 and it is exactly the same file size regardless of what DPI you tag it with - it's just 1000x667 pixels.  The image is 667,000 pixels in total, how many pixels there are per inch doesn't matter.  The file size will be 667KB before JPEG compression (assuming an 8 bit per pixel file which JPEG are).  Whether you tag it with 1DPI, or 1,000,000 DPI does not matter.

[Paul2660]

Ok.

Thanks. This is something I did misunderstand. That helped.

Paul

[BJL]

Paul2660's sententiment is correct anyway: normal web viewing is on a screen of far less than 22MP, and  indeed of lower resolution than is delivered by any current ILC (either DSLR or mirrorless).

[Telecaster]

Even 8K displays—which don't yet exist commercially and likely won't for some time—require "only" ~45mp from a 3:2 sensor, or ~50mp from a 4:3 chip, prior to ~16:9 (8192x4320) cropping. (Unless, that is, you get into mapping RGB sensor photosites directly to RGB display sub-pixels.) We're already there, when it comes to relatively affordable gear, with the Pentax 645Z & the new Canons. Soon there'll be the next Sony high-end FE-mount camera(s) too.

-Dave-

[dwswager]

Pardon my ignorance, but I have a few questions. DXOmark's mpix ratings have generated several discussions because they seem to show that most lenses don't match the resolution of high megapixel cameras like the D810. There are a couple of threads out there that address the issue, but they tend to get very technical without getting to the punchline (or maybe it just went over my head).

So here are a few direct questions:

A 36mp camera will produce 50% greater resolution than a 24mp camera even if the lens resolution on both cameras maxes out at 22mp - correct?

If so, will it make a noticeable difference on a 16x20 print?

Assuming you are starting with 36MP or 24MP you will not notice a difference, except is exceptional circumstances.  But I would argue for the 36MPs for a whole host of other reasons.

Also, while 36MP is 50% more pixels than 24MP, it does not equate to printing 50% bigger, only 50% more printed area.  Assuming a base of 12MP, it takes 48MP to print make a print twice as large (8x10 to 16x20) at the same pixel density.

I was deciding between the D810 and D750 because I didn't think I would need the extra pixels.  Boy, am I glad I bought the D810!  First, I can shoot it at 1.2X and 1.5x crops to get more reach and still get 25MP and 15MP! 

I shoot multi-shot images and the extra pixels can mean a shot or 2 less needed to give the same pixel dimensions or you might even be able to shoot in landscape instead of portrait.  In most situations, this might not be a big deal, but with tough conditions or quickly changing light, the ability to execute the sequence quicker is a big benefit.

It provides for cropping and re-purposing images.

Basically, what I'm saying is that the extra pixels gives you options!  And it really isn't that big a deal as far as file size and processing time goes.  4 or 5 years ago, it would have been an issue, but now not so much.

[BJL]

Assuming you are starting with 36MP or 24MP you will not notice a difference, except is exceptional circumstances.  But I would argue for the 36MPs for a whole host of other reasons.

...  First, I can shoot it at 1.2X and 1.5x crops to get more reach and still get 25MP and 15MP!  

...

It provides for cropping and re-purposing images.

Basically, what I'm saying is that the extra pixels gives you options!

Yep! That is the way I feel already about my progression from 5MP to 10MP to 12MP to 16MP: those 16MP are not all needed for my final (mostly on-screen) display purposes, but the telephoto and macro abilities of my lenses are lot better than with those same lenses on my older, lower pixel count bodies!