CatMarley Loc: North Carolina

I don't remember where I picked this up, it is not mine, but thought it would make a good topic for discussion.

The megapixel myth
OK, so the sensor’s good, but there are only 16MP. This was probably the one thing that put me off most at first. As I mentioned, I started out with an 8MP 20D, then upgraded to a 12MP 5D, then a 21MP 5D Mark II, then a 24MP Sony A99, and each time I considered it an improvement. And it was – the sensor in each camera was better than the previous model – but how much of this could be attributed to the increase in megapixels and how many megapixels do you actually need? If you’re shooting high end fashion, or architectural work that will be blown up to the size of a house and then inspected with a magnifying glass, then you need a fair amount, but how many do the rest of us typically need?

The human eye can only resolve a finite amount of detail (see this link for a detailed explanation). At best this is somewhere around 200 points or dots per inch (DPI) so if you have an image from an X-T1 that produces images that are 4896 pixels by 3264 you can create a 24.5″ print. At this size of print, even if we add more megapixels we’re physically incapable of perceiving the extra detail.
When we create a larger print wouldn’t more megapixels be an advantage? For example, with a file from a D800 (7360 pixels by 4912) you can create a print that’s almost 37″ wide at 200 DPI. On the face of it then, more megapixels equals higher quality large prints, but this doesn’t take viewing distance into account.

Viewing distance is normally taken to be 1.5 the diagonal size of an image, so a 6″ x 4″ print would be viewed at about 11″, a 37″ x 24″ print at 66″. Because the 37″ print is further away the maximum DPI we can perceive at this range is somewhere around 50: we can’t make out the finer detail because our eyes can’t resolve that level of detail at that distance. Admittedly, you can stick your nose to the print, at which point you may be able to tell the difference between a 200 DPI print from a D800 or a 132 DPI one from an X-T1, but a) these differences will be small, and b) at normal viewing distances the differences between the two won’t be apparent.

Put another way, if you take viewing distance into account anything that shoots at 12MP or above will produce an image with sufficient detail for a high quality print, from a 6″ x 4″ postcard to a billboard across the street.

dirtpusher Loc: tulsa oklahoma

only thing i see need for is to make better murals out of the picture.

lamiaceae Loc: San Luis Obispo County, CA

I and many others agree with you (this post), but I would imagine that many other UHH members will want to argue for a never ending pixel race to the limits of Diffraction (already met for most of us unless you shoot at f/1.2 all the time). So many people find they have to justify their succumbing to marketing by buying ever higher pixel count sensors. For nearly anyone a 18 MP "DX" format or 24 MP "FX" sensor camera is all you need. Higher quality lenses and processors would be much more useful. Note, Nikon Dx (single digit name) series. My view due to the physics of optics, a 50 MP sensor at f/22 is pointless! There the pixels being as tiny as they are in even a 36 MP "DX" or "FX" sensor, groups of pixels would be "blurred" by a huge circle of confusion. Now, in the future, a non-Beyer array sensor might be a whole different story. But there would always be limits (and we are close to them now).

Analogy, how many 16GHz 1-core computer microprocessors do you see? 4GHz 4-core, yes!

;-)

rjaywallace Loc: Wisconsin

Based on camera body specs currently common on the retail market, I would say 16-24 MP is a typical range for average non-professional users. In effect I'm saying the market is dictating what we "need" as opposed to photographers telling the market what they want.

rmalarz Loc: Tempe, Arizona

Excellent points made here, Cat. Especially, the viewing distance, which some on UHH think is the length of their nose.

Additionally, the more pixels, the more photosites. Thus, the size of the photosite decreases in size. The smaller photosites are prone to be noisier.
--Bob

Rongnongno Loc: FL

What is never mentioned is that a greater concentration of pixels allows for a greater resolution of details but that... Who cares? Right?

It is not for nothing that on high end cameras the AA filter is being removed. There is no need to hide the jagged edges as they are minimized. Add to that that the greater resolution also means a reduction of moire... Who cares?

This particular aspect trumps everything else.

Enjoy jagged edges AA softening filter moire and flawed reasoning.

CatMarley Loc: North Carolina

Yes. The only advantage to more pixels I can see is a substitute for framing the shot in the viewfinder and depending on using only a small crop from the files you take. And in some cases this IS necessary. When shooting fast moving puppies I always give them a lot more room in the frame, and crop as needed later, because you never know which way they will move before the shutter fires. If you are routinely only printing 25% of a frame, then 36 MP may be what you need for decent prints.

mdsiamese Loc: Maryland

This assumes that the only use for more pixels is for those who want to enlarge images. It overlooks cropping.

I have a Nikon D810, and various lenses. There are times when I just cannot frame the shot to fill the frame. If my subject is only 50% of the image, then cropping takes my 36.3 MP down to 18 MP. You cannot always move forward or switch lenses to fill the frame.

I do like having the ability to crop an image and still have enough pixels to do a good enlargement or make a nice print.

There are many factors that I consider first before the number of MP when choosing a camera, low light sensitivity being one of the biggies. But doesn't the MP race facilitate improvements in sensors and low light sensitivity?

CatMarley Loc: North Carolina

I don't agree that more detail with more pixels is never mentioned. I think it is repeated all the time. In fact it is the prime selling point of more pixels. I think this article made the point that the eye cannot distinguish those fine details at normal viewing distances, and unless you are doing photomicroscopy those extra details will be lost at normal viewing distance. The need for antialiasing filtration can be eliminated at the sensor level as Fuji has already done. This also reduces moire effect.

CatMarley Loc: North Carolina

Does it? I am not sure that Canon is developing better low light capability because it put 50 MP on it's Full frame sensor. But I know nothing about the direction of that research. Of course I agree that cropping is better with more pixels to use. But it has made me lazier, I think. I used to be much more careful to frame shots properly when I knew I would have to project the whole slide at my camera club meeting. Plus the film and processing cost a lot! I couldn't afford to snap away with abandon!

robsphotography Loc: New Zealand

Yes indeed, I own the 42.4mp full frame Sony A7RII and I think the ability to crop an image substantially and still get a reasonable-sized print from the crop is a big advantage when compared with owning a camera which has a lot less megapixels!

I have asked people on forums about what they think are the advantages and disadvantages of cropping images instead of using lenses with longer focal lengths and I have summarised their views on this interesting (and important) topic here:

http://www.robsphotography.co.nz/focal-length.html

And for very large prints, of say, 40 inches width or more, the amount of detail you can see in such prints from Sony A7RII images is amazing and buyers just don't want to purchase large slightly blurry prints (often for sale on canvases) again!

Regards
Rob

PixelStan77 Loc: Vermont/Chicago

What is the bottom line from this?

selmslie Loc: Fernandina Beach, FL, USA

Your numbers are in line with the other general assumption of 300 DPI when viewed from 10 inches (25 cm) - about the most anyone with normal vision can distinguish. If you work out the numbers, 9 MP is all you need in a 2:3 sensor - anything more is overkill unless you are in the habit of wasting your capture with a lot of cropping. And of course, the larger your print the further back anyone will need to stand, which leaves the 9 MP constant.

Additional MP offers a safety factor and a little extra sharpness. There is good reason why some of the best professional cameras have been staying between 12 and 20 MP. When the pros actually need additional megapixels they can get it with medium format or film.

Many (not all) of the most outspoken proponents of high MP cameras can't actually use one to produce a decent photograph. They are just arguing numbers and are afraid to post images.

What is not often mentioned is that, if you are going to take advantage of a high megapixel camera, you will need to invest a lot of money in new, high quality lenses and you should be shooting from a sturdy tripod at a low ISO.

lamiaceae Loc: San Luis Obispo County, CA

I have to keep bringing this up: Diffraction is a function only of pixel size (smaller for higher density) and aperture, it has nothing to do with the physical size of the sensor. Does not matter if it is 17x23mm, 24x36mm, or 6x7cm. If you stop down for more DoF (or any reason for stopping down) the image gets fuzzier as the circles of confusion get larger. Canon and Nikon and who ever can not change the laws of physics (quantum mechanics). Cropping due to not using all the sensor is a bad choice in any case but to salvage an image. Use the correct lens and distances. Many people seem to need to actually try it, making large prints to see the diffraction limit effect on pixels (size) and stops. There is plenty of info on the WEB about it.

LarryFB Loc: Depends where our RV is parked

I completly agree with you. I have a 16 Megapixel camera which seems to be great for what I shoot and want to print. I am very happy with 16 megapixels. Yes, depending on cost, some day I may get a new camera at 24 MP, but only because the camera has the features I want, not because it is 24 MP.