Monday, February 25, 2013

Don't be MegaPixel Obsessed

These days cameras come with MegaPixels as high as 20 to 30 MP and most cameras offer a wide range of image resolution settings. Let us quickly look at the costs and benefits of MegaPixels in a practical way. Like many things in modern life, we believe in ‘bigger the better’.  So many of us, without thinking much, use the camera in the highest resolution it offers. However we need to have a reason for choosing a 20MP resolution for a photo that you are never going to print. Most computer monitors CAN’T display more than 4 Mega-Pixels. Your smart 1080p HD-TV can show only 2 Mega-Pixels.

How to choose an optimum resolution setting on  your camera?

Think about the biggest photo or poster you have printed so far or you see yourself printing. Most of us never print beyond 4x6 inch prints or maybe 8x10 inch prints once in a while. If that is true, a 20MP photo or a 4MP photo when printed as a 4x6 inch print or 8x10 inch print would not bring you any more sharpness or clarity in the photos printed at Costco,  Shutterfly, or photo labs in most stores like Walgreens, CVS, Target, Walmart etc.

Here is the resolution typically required for various prints or for viewing.

Print Size in inches
Pixels required for printing/viewing
 MegaPixels in image (Rounded to nearest full number))
1600x2000 (@200 dpi printing (most stores print at 150 dpi)
1380x2070 (from website)
16x20 Poster print
1840x2300 (from website)
Viewing a photo on a 1080p HDTV
1920x1080 pixels
Viewing photos on a 22” LED monitor
1920x1080 pixels
Viewing photos on a 30” LED monitor
2560x1600 pixels

For many situations, like photos in some party, if you know that you are not going to print any photo in a size bigger than 8x10 inch, you can save space on your memory card, on your computer, or conserve bandwidth while emailing photos or uploading them on Facebook by setting MP to 6 to 8MP instead of using camera’s maximum resolution of 16 or 20 MP.

Costs of taking unnecessarily large resolution photos:
1.      No obvious gain in sharpness or clarity in printed photos: Too much resolution does NOT make your 4x6 inch or 8x10 inch prints any sharper or more colorful. Most printers can’t print more than specific DPIs. Evenif a printer can print very high DPIs, human eye will not be able to distinguish any difference. (Read about Retina Display in iPads or MacBook Pro. That is the maximum DPIs that make an image look smooth and continuous to our eyes. iPads has 264 pixels per inch and MacBook Pro has 227. This also depends on from how far you are looking at the picture/screen. A 18x24 poster viewed from 3 feet away doesn’t benefit from as many DPIs as a 4x6 inch photo viewed from a feet away)
2.      No gain when viewing photos on a monitor or an HDTV: When you look at the photos on the computer screen, or on your HDTV, maximum resolution is normally 1280x720 pixels which is around 1MP. For higher resolution computer monitors, it can be no more than 3MP. So a 20MP photo would NOT appear better than a 6 MP photo on computer or on your HDTV.
3.      Can save more photos on your Memory cards, on your computer Hard Disk or on you back up drives: By keeping size to 6MP instead of 18MP, you can store 3 times more photos on your memory card.
4.      Save time while transferring, uploading photos: Downloading photos from the camera, or uploading them to Facebook, can also save you time and bandwidth with 6MP photos compared to 18MP photos. Facebook, at the time of this writing, does not display an image in more than 2MP resolution.
5.      Use the camera’s power for something more useful: In many situations, it is advisable to take multiple shots consecutively to capture the right moment. As an example, when your child is playing soccer and you want to capture the perfect moment. In most cameras, if you select a lower resolution, you can take more photos in a second- frames per second (FPS). As an example, with a 16MP setting, your camera can take say 4 photos in a second but with 6MP setting, your camera can take up to 8 photos in a second. This gives you better odds in capturing the right moment.

Potential Benefits of Higher Resolution photos:

1.      Using High Resolution when you can’t zoom in: If you don’t have a zoom lens, a higher resolution photo can come handy. If you want to take a photo of something specific but you can’t zoom in, set your camera to the maximum resolution it supports and then crop out the unnecessary things from the photo. This way what you wanted in the photo is still in high resolution.
So in short, a high resolution can sometimes be useful as a zoom lens.
2.      Avoid regrets: If you took a photo that came out too good and you simply loved it. Say you want to make a life size portrait of your kid’s photo. In such situation, sometimes it is too later if you took photo in only 6MP mode. You would regret why you didn’t take photo in highest resolution your camera offered! So it is a choice to make. You can take a rational approach or try to cover all possibilities and decide to take each photo in 20MP. Would you take 10000 20MP photos to avoid one photo down the road that really would have benefitted from 20MP!

In my opinion, if you are probably not going to print photos in print size bigger than 12x18, but want to keep options open, take photos in 10MP mode. Or depending on situation, keep changing resolution setting on your camera. When taking photos for selling items on eBay or Craigslist, I set my camera to 2MP mode. Taking photos of kids at my son’s birthday party or during his soccer game, I would set camera to 6MP. For family photos and photos of friends, I set it to 10MP. When I come across beautiful landscapes or am taking portraits, I set camera to the maximum resolution it offers.

Which Camera is better? A 20 MP or a 30 MP Camera?

When it comes to buying a camera, often times you have to choose between cameras that have different Mega Pixels capacity. Provided a camera has more than 10MP capacity, I would prefer to buy a camera with lower MP than the one that has higher MP assuming sensor size is same. For same sensor size, one camera model can have 30 million pixels stuffed on it and other camera model may have put up only 16 million pixels on it. Naturally the more MP you put on same sized sensor, each pixel gets smaller. The smaller a pixel becomes, it loses some sensitivity to light and hence the pictures are likely to get more noisy at higher ISO.  As in my world, there is really no benefit in going more than 10-16MP, I would prefer the camera with 16MP compared to the one that has 30MP. to get bigger pixels, better capture of light and better sensitivity to light.


My Camera Seems to Take Grainy or Noisy Photos

Fortunately, you are not alone. This is a very common issue with most cameras, including consumer SLR cameras.
If you have noticed, most of the time, this happens when you are taking photos in Auto mode specially in low light. A camera needs some fixed amount of light to take a good photo and the light enters through the lens on the camera and gets captured by its sensor. There are 3 things that a camera can control to get the enough amount of light it needs. 
1) Shutter speed: When you click on the Shutter Release button on the camera, the shutter opens up for some amount of time to let the light pass through the lens. Your camera decides the speed of the shutter based on many factors. If you are taking a photo in a low light, the camera would need to keep the shutter open for longer time but Camera knows two important restictions. (i) First one is the shake in you hands. Most individuals can't hold a camera or anything as such, perfectly steady for more than 1/75 seconds. Surprised? Please don't. A minor shake in your hand will cause the photo to be blurry. (ii) Even if you have steady hands, or you use a tripod, most of the time, the thing you taking a photo of will move. Most of the time, we take photos of people. They also move during a fraction of the second. A kid or a pet will move more quickly then an adult but we all constantly move. Our naked eyes may not see the move but a camera lens will capture it. If you are taking a photo of a landscape which has a tree, a minor breeze of air will cause the leaves to move.
In short, photographer as well as most subjects move quickly, most cameras will try to avoid shutter speed slower than say 1/75 second. This is a restriction imposed by camera's software to save your photos in most situations by avoiding chances for blurr.
2) Lens Opening. The technical term is Aperture. Most compact cameras have tiny lens openings. The wider the opening, the more light a camera can take. However most sub $1000 camera's have ordinarly lenses which do not allow too much light to pass through. No surprise a fast lens sometimes costs much more than a  best compact camera you can buy.
In short, for this Lens Opening, your camera doesn't have move room to play around. This is a camera's hardware restriction.
3) Sensor's sensitivity. The technical term is ISO. When a camera runs into the first two limitations (of limited shutter speed and lens opening), the only option it has is to increase the camera's sensitivity to light. This is like increasing sensor's receptivity to light. Camera can play up to some level of higher ISO but the more ISO or sensitivity it increasing, the image starts getting noise.  The noise is the unwanted pixels or grainy look in the photos. If you want more tech details about noise, see the Wiki post :
For most compact cameras, when the ISO is set to more than 400 or 800, you will start seeing the noise.
Now having learned about the 3 main things a camera can control to take a nice photo for you, if you see your camera take a bad photo, it is probably not your camera's fault. This is similar to many limitations we run into our daily lives. I like to run a marathon but I know I can't run more than 3 miles. I like to make a million dollars a year but I know most of us can't. Same way, you and your camera wants to take a great photo but many times it can't.
So what do we do to take better photos?
*** Take photos in better light:
* If possible take photos in good light- natural or artificial. Make it easy for your camera to help you out.
* If lighting is dull when you are taking photos, set camera ISO to 100 (200 or 400 at most) and add more artificial light. Or, simply turn on Camera flash. Use the camera in Fill Flash mode. You will get some shadows or washed out faces but that would be better than ghost looking blurry photos. In the next article, I will show you how to avoid shadows or over-exposure too.
*** Use Tripod when taking photos of stationary or slow-moving objects:
* Use Tripod and set Camera to Av Mode with ISO fixed at 100, 200 or 400 only. If you are taking photos of people or pets, use the smallest F number on the camera. If you are taking a photo of a landscape, set it to 8 or so. In Av mode, you decide the ISO and Aperture and let camera decide the shutter speed. Because you are using a tripod and the you are taking photos of a stationary object, camera can use a slow shutter speed and can shutter open as much as it needs. You will see nice beautiful non-grainy photos.
*** Buy expensive cameras or a fast lens:
* However use of a tripod or slow shutter doesn't work when you are taking photos of people or pets. They usually move within a split second and that causes photos to get blurry with slower shutter speed. To overcome this too, use some faster lens like 1.4, 1.8 or 2. This will help camera take lot more light while shutter is open. Also, more expensive camera's have bigger sensors and a bigger sensor does help with better control of noise. Also an SLR can take less grainy photos with ISO as high as 1600 but a regular compact camera would have noisy images when ISO starts getting above say 400.

(My friend was using a kit lens on his Nikon and I used a fast lens on Pentax to take photos in the same light. Because of a fast lens, my photos had much or almost no noise. Here is one photo: )