First of all, I must say that I have resisted the urge to write this post for over a year because I know I am going to get dozens of comments saying nothing more than “Megapixels are unnecessary–I want ISO.” I often think that photographers simply repeat what they have heard other pro photographers teach online, and stick to it instead of investigating things on their own.
Before I get nerdy on you, allow me to provide some background if you're newer to this debate. On a camera sensor, there are millions of light receptors (called photosites) that collect information about how much light is present, color, and other information. It used to be, in the early days of digital photography, that camera manufacturers could only fit 2 or 3 million pixels on these sensors. Now, a sensor of the same size can contain 30 or more megapixels. The problem with the proliferation of mexapixels on a sensor is that it reduces the space available for each photosite. The smaller the photosites are, the more difficult it is for camera manufacturers to create cameras that can take pictures with high ISO levels and still maintain a low amount of digital noise. So many photographers argue that they don't want camera manufacturers to keep adding more megapixels on a sensor, and would prefer that the manufacturers instead focus on low light performance.
I COMPLETELY understand this sentiment. I have missed many pictures in low light environments because my camera simply couldn't take a clean picture without adding more light to the scene with a flash. I understand that if all else is equal, the camera with fewer megapixels will produce images with less noise because each photosite has a larger area of light to gather from. I get it. Really–I do. This mirrors a conversation I had with Scott Bourne a few weeks ago at the Google+ Photographer's Conference, where he argued that the new Nikon D800 (which has 36.3 megapixels) should not be used by portrait photographers because it has too many megapixels. I very respect Scott, but we disagree on this point.
UPDATE: Scott commented below and mentioned an article (which I hadn't read yet) where he explained his position in more detail. You can read that here.
Basically, there are two reasons why I believe megapixel count should not be discounted: (1) Megapixels future-proof your images, and (2) Megapixels allow photographers to crop significantly.
Future-Proof Your Images with Higher Megapixel Cameras
My first digital camera had 2.3 megapixels. At the time, I remember other photographers telling me that it was plenty big to show the photos on a computer or to make small prints. Now, only 8 years later, photos from that camera are not even capable of filling the screen of my laptop.
This begs the question: Do you want your entire photo library to look outdated in 8 years?
Obviously, the argument against that point is that digital cameras have improved dramatically since my tiny 2.3 megapixel camera, and now that we commonly shoot cameras between 10 and 18 megapixels, we've hit a sweet spot where resolution does not need to improve. Photographers who believe this are quick to point out that even a 10 megapixel camera can print perfect photos at 11×14″.
I believe that this argument is short-sighted. First of all, I'm not talking about print size. Digital cameras have plenty of resolution to make large prints, and frankly, it's rare that I feel the need to print. Most of my photos are viewed on computers.
Speaking of computers, computer screens are currently undergoing a major transformation. In January 2012, the mean screen resolution of a computer was 1366 x768; however, newer computers are coming out with incredibly improved screen resolution. The reason for the improved screen resolution is that screens are being held closer and closer to the viewer. My 55″ TV looks fantastic when viewed from across the room, even though it only has 1080 pixels on the short edge. But now that iPads, phones, and other mobile devices and laptops are the most common way to view the web, the screens are only a few inches from our eyes (centimeters), meaning that we are able to see sharp details better.
In fact, the new Macbook Pro Retina Display has a resolution of 2880 x 1800 at 220 pixels per inch. While that is a dramatic improvement, it still amounts to only 5 megapixels, which is fewer pixels than any modern DSLR. So why do I think 10 megapixels is too few? Because I want my images to look fantastic 10 years from now.
Increased Megapixels Allows for More Cropping
This argument for more megapixels was taught to me this last year while shooting photography in Yellowstone. I was equipped with a 600mm lens from BorrowLenses.com and a 1.4 teleconverter. That means that I was shooting at 840mm. The lens was like a bazooka!
Even though I was shooting with the highest-end gear and the longest lens I could find, I often found myself just barely out of reach of some of the wildlife in Yellowstone. In one particular instance, there was a beautiful red fox posed against the white snow that was just a bit too far for my lens to reach. My camera had 16 megapixels, but when I cropped in to where I wanted the composition to be, there simply weren't enough pixels to have the quality and detail that I would like. Opportunity lost.
In fact, I find that this is frequently the case. When I'm out shooting, I sometimes frame the shot to the composition that I would like, but then return home and find that I cropped in too tight. With more megapixels, I could always shoot slightly wider than I imagine, and then crop in to the exact spot in Lightroom without worrying about losing detail in the photo.
A prime example of megapixels over focal length was mentioned by Juan Pons a few weeks ago on his excellent podcast. Many wildlife photographers continued shooting the Canon 7D rather than upgrading to the 5D Mark II because the 7D is a crop sensor camera and therefore adds to the focal length of the lens (if you're new to this concept, read this article). For wildlife photographers, long focal lengths are essential. However, photographers discovered that the 5D Mark III (a full-frame camera and thus shorter effective focal lengths) is actually is better than the crop sensor 7D for focal length, because its increased megapixels allow photographers to crop in more with the same number of pixels than the 7D can crop in effectively with its crop multiplier due to the sensor size.
BUT WHAT ABOUT LOW LIGHT PERFORMANCE!?!??!
What photographers have discovered in the last few months since the D800 was released is that its low light performance is actually quite superior, despite the high megapixel count on the sensor. In fact, it performs better at high ISOs than its D700 predecessor even though there are nearly three times more pixels on the D800. Although the size-per-pixel argument makes perfect scientific sense, it ignores the reality that camera manufacturers have seemed to defeat the physics with advanced noise reduction in the camera.
Another interesting finding among photographers who are experimenting with high megapixel cameras is that, even if these cameras produce more noise, the fact that they capture such fine detail allows photographers to use aggressive noise reduction in Photoshop or Lightroom without losing a significant amount of sharpness.
You see, software tools such as Photoshop and Lightroom are capable of eliminating noise in photos, but the noise reduction always reduces the overall sharpness of the photo; however, if a high megapixel photo is used for the noise reduction, there is enough fine detail in the picture that the noise reduction does not affect the file as much, so more of it can be applied while maintaining sufficient sharpness.
For example, the D800 produces slightly more noise than the Nikon D3s, but if you apply noise reduction to photos from both cameras, the D800 file can take more noise reduction and still retain more detail. When noise reduction is applied to a file from the D3s, the picture falls apart because there are not enough pixels of information to apply much noise reduction. More on that here.
Therefore, if noise reduction is taken into account, high megapixel counts can produce files with less noise.
One More Thing… (Okay, maybe two)
I currently have a Nikon D800 on order (it has been on order FOREVER, so I'd appreciate it if Nikon would ship me one!). It is a $3,000 camera and wields an powerful 36.3 megapixels sensor. For me, this camera is nearly ideal. HOWEVER, I want to respond to a few drawbacks that many photographers have mentioned about shooting a camera with this many megapixels.
1. Shooting portraits with too many megapixels shows too many imperfections in the skin. HUH!!??! I have to admit that I was shocked when Scott Bourne cited this as a main reason for not liking the D800. Using a camera that is incapable of capturing fine detail is a horrible way to smooth skin. Skin smoothing is extremely easy and fast using Photoshop or Lightroom. You don't have to take low-detail pictures just to have good looking skin. Further, this ignores the fact that there are parts of a person that you WANT incredible detail when shooting a portrait (like the eyes, the hair, the lips, etc).
2. Shooting high-resolution cameras makes for unwieldy file sizes. This is a very relevant argument for some photographers. In our studio, I use a BLAZING fast computer and we have 12 terabyte network attached storage devices, so file size is not an issue in the least. However, for photographers who do not have this type of equipment, I can see it being frustrating to work with such large files.
So yes, I DEFINITELY agree that if you're not equipped with computer equipment to work with high megapixel cameras, then a high megapixel camera probably isn't a great choice.
But then again, keep in mind that storage is much less expensive than a quality long lens. A wildlife or sports photographer who can't spend $10,000 on a quality 400 or 600mm lens could get quite a bit of “focal length” by using a high megapixel camera and then cropping on the computer. Storage is cheaper than a long pro lens.
I apologize for this post being a bit argumentative and overly technical, but I just can't stand seeing such a good debate passing by without taking the chance to toss in my two cents 🙂 Also, I hope that you'll at least consider things from my point of view before following the photo lemmings on the web who simply repeat the photo advice that they hear others say, because the truth is that there are some very compelling reasons to embrace new technology with high megapixels.