Click to open network menu
Join or Log In
Mobafire logo

Join the leading League of Legends community. Create and share Champion Guides and Builds.

Create an MFN Account






Or

's Forum Avatar

Camera sensors: why size and megapixels matter,...

Creator: Searz January 27, 2015 6:48pm
Searz
<Ancient Member>
Searz's Forum Avatar
Show more awards
Posts:
13418
Joined:
Jun 6th, 2010
Permalink | Quote | PM | +Rep January 27, 2015 6:48pm | Report
First off, let's beat the most common misconception right out of you.
MEGAPIXELS DO NOT REPRESENT QUALITY.
More of them is not always better, in fact it many times isn't. The article below will hopefully allow you to understand why.


First I need to explain the concept of shutter speed.
Shutter speed is the amount of time that the camera sensor is exposed to light, which it then forms an image out of. The brighter it is the more light is captured. The more light captured the shorter the exposure needed to capture the image.
When it's bright outside you might be able to get away with shutter speeds of 1/2000s. While taking photos in darker environments often ends up forcing the shutter speed down to about 1/40s to capture enough light for a visible image.
If we assume that both images caught roughly the same amount of light, then what difference does the shutter speed make? Well, for a person or object to be completely sharp in an image it is required to stay almost still for the entirety of the exposure, because if it moves while the sensor is still capturing light then the image being captured will have captured light from the moving object in all of its positions. This turns the object into a blur, spreading across the area where it moved during the exposure. Same thing applies if the camera itself moves, only now the entire image turns into a blur, instead of just the object.
Slow shutter speeds of as little as 1/30s require stationary subjects and steady hands to operate. Shutter speeds below that should be avoided when shooting hand-held. Only when using a tripod should you go any slower than that. Tripods allow for some very beautiful shots in darkness, because the shutter can remain open for as long as it needs to collect the necessary light. 1-30 seconds, or even more.
When taking photos of moving subjects in darkness you usually end up sacrificing a lot of quality because most cameras can't keep up with the increase in sensor sensitivity required to gather enough light. Flashes fix this, but only work for subjects that are close to you, usually becoming useless when 10+ meters away from the subject and flashes also tend to destroy the white-balance, changing the color of the light in the scene to a white hue.
Fast shutter speeds allow you to freeze movement, while remaining sharp. Animals and wildlife usually require a shutter speed of at least 1/100s to remain sharp, because of their tendency to move around. Taking photos of sports or other fast movement usually requires shutter speeds of at least 1/250s to properly freeze movement. Shutter speeds as quick as 1/4000 allow you to freeze raindrops in the air.

Next up is the ISO.
ISO is the sensitivity setting of a digital sensor. 100 is the default lowest sensitivity. At this setting you'll get the darkest image with the smallest margin for error (i.e: the closest to real life, highest quality). This margin of error shows up as large numbers of small specks of light of differing colors, where they shouldn't be. Most of this can be worked out by the camera's noise reduction functionality, but detail and color accuracy takes a hit in the process.
Then for each step up from 100 you are doubling the sensitivity of the sensor, and thus doubling the light in the image, but at the same time doubling the margin of error. I.e: increasing the strength of the specks of light, making them more visible, which kills a lot more detail when removed through noise reduction). And sooner or later you get to a point where the margin of error is almost as big as the signal, which pretty much makes the image unusable.

A sensor is divided into pixels. 8MP means 8 million pixels, or mega pixels, since mega is short for 10^6. We can then divide the total area of the sensor by 8million for a rough idea of the area which captures the light for each pixel. The actual area is much harder to get an idea of since there is circuitry and other things also present in the same area.
This leads us to two conclusions:
1. Less pixels equals more light captured per pixel(at the same sensor size).
2. Larger sensors equal more light captured.

From this we can conclude that high numbers of pixels are bad for ISO-performance.
Which when paired with the rather small volume allotments of modern smartphones means that you should probably not opt for 20MP in a phone when the sensor is a fraction of the size of a normal camera. This is something only Apple seems to have realized with their frequent use of 8MP sensors, and for that I must applaud them. *cough*although I don't like many of their design decisions in iOS*cough*
The actual size difference between a full-frame sensor and the average phone sensor is 864mm^2 to 17mm^2. A full-frame sensor is a whopping 50 times larger than the average phone sensor. If the phone and camera are assumed to have the same number of pixels and use the same technology then a full-frame camera would capture 50 times more light. But this is not the case, phone sensors are more advanced since they are smaller and thus cheaper to make. The real difference is roughly half of that: 25 times. This is mainly due to the technique called BSI (Back Side Illumination), which moves all the circuitry to the backside of the sensor, freeing up more space to capture light on.
And the tiny size is essentially why phones run into problems capturing detail around 800ISO, while full-frame sensors can go all the way up to 12800-25600 (16-32 times more light) before they run into the same problems.
With 6400ISO a camera can use a shutter speed of 1/500s, properly freezing most movement, while 400ISO would require 1/30s to capture the same light at the same aperture(will explain aperture in a later installment), which would turn even slower movements into a blurry mess. This is why ISO-performance is important to many people. Only in special circumstances(like a well-lit studio) can one ignore its effects. And this is why the rush to cram more megapixels into our cameras is bad.

Another benefit of larger area per pixel is increased dynamic range. Dynamic range is the range of differing light strengths that can be seen at any given time. Take for example a photo of bright light and dark shadow. The highlights, i.e: the area around the light are completely white due to the maximum capacity of light of the pixel being reached. While the darkest areas are completely black due to the lack of light captured from there. To capture light in the shadows you will have to expose longer, but doing so will make an even larger area around the light go completely white, while the opposite happens when reducing exposure to save detail around the light source. You're pretty much doomed to lose detail in either or both of the areas in the scene no matter what.
Having larger pixels increases the maximum capacity of light the pixel is able to capture. While also at the same time being able to capture enough light from dark areas for the sensor to register a light value above 0 (zero is black).
This increases the range of differing light strengths that can be captured in an image.

Here's a nice image that illustrates the difference between phone sensors and large camera sensors. Full-frame is the very largest (on this chart) and phones are usually close to the very smallest.


Is there anything in the article that you don't think I explained enough, just go ahead and ask. I will try to answer and revise as best I can.


Interesting cameras that I'd like to point out in relation to this topic are the Sony A7S, a full-frame camera with 12MP, specialized in low-light performance, and the Samsung NX1, the world's first ASP-C sized sensor with BSI technology.

Sony A7S


Samsung NX1
"Games may not be art, but this one did wonderful things to my ****." - Roger Ebert

"I AM PRETTY SURE THIS MANGA IS VIOLATING SOME LAWS ABOUT CHILD PORNOGRAPHY

I CANNOT GET ENOUGH

****" - mencretnas, on Gigantomakhia
Toshabi
<Veteran>
Toshabi's Forum Avatar
Show more awards
Posts:
5946
Joined:
Jan 18th, 2011
Permalink | Quote | PM | +Rep January 27, 2015 6:52pm | Report
That came ojt of no where for Searz, but it was a nice review of my photography courses. Just about everything he says is pretty spot on.



Kinda sad Nikon didn't get any love.
IceCreamy wrote:

(1:07): I prefer your balls over ***hol












Searz
<Ancient Member>
Searz's Forum Avatar
Show more awards
Posts:
13418
Joined:
Jun 6th, 2010
Permalink | Quote | PM | +Rep January 27, 2015 7:26pm | Report
Toshabi wrote:
That came ojt of no where for Searz, but it was a nice review of my photography courses. Just about everything he says is pretty spot on.

Thanks. Nice to see that my self-taught knowledge holds up :)
Quoted:
Kinda sad Nikon didn't get any love.

Well, they aren't really innovating much at the moment.
They are pretty great at capturing detail in shadows, especially compared to Canon(which suck at shadow detail), but it's still nothing truly remarkable.

Both of the giants Canon and Nikon are slowly falling out of favor due to lack of innovation and reluctance to prioritize mirrorless AKA CSC (Compact System Cameras) for the enthusiast market.
CSC is definitely the way going forward. The only major disadvantage right now is battery life, which can be solved by carrying an extra battery. Other disadvantages are viewfinder lag (which now sits at below 5ms, barely noticeable) and focus speed, which is pretty much the same in good light and a bit worse in low light.
While the advantages are numerous and great, including: exposure preview, focus accuracy, video functionality, advanced digital processing, size and weight.
"Nothing says I like you more than letting you drink my filtered urine." - deityignis

"MY WHOLE LIFE IS A WANK." - WTTNHK

"There are boobs...LOTS OF BOOBS. And then Obama comes out of no where." - JEFFY40HANDS, on Air Gear
xIchi
<Member>
xIchi's Forum Avatar
Show more awards
Posts:
1806
Joined:
Oct 19th, 2010
Permalink | Quote | PM | +Rep January 28, 2015 10:29am | Report
Toshabi wrote:
That came ojt of no where for Searz, but it was a nice review of my photography courses. Just about everything he says is pretty spot on.



Kinda sad Nikon didn't get any love.


This didn't come out of nowhere. I think they talked about something in some other OT thread and came to the conclusion that this should have it's own thread.

I once wanted to do Photography as some kind of hobby, but then realized that equipment can be super expensive.

Now I regret it as I visted alot of places in Germany and around Germany with my mates and could've taken awesome pictures q_q
Searz
<Ancient Member>
Searz's Forum Avatar
Show more awards
Posts:
13418
Joined:
Jun 6th, 2010
Permalink | Quote | PM | +Rep January 28, 2015 10:59pm | Report
Added a couple of images as examples.
Here they are, for quick reference:
Super fast shutter: https://www.flickr.com/photos/128704531@N08/16388169825
Fast shutter: https://www.flickr.com/photos/128704531@N08/16393293085
Long exposure (taken at night): https://www.flickr.com/photos/128704531@N08/16206035580
High contrast: https://www.flickr.com/photos/128704531@N08/16207068429
"Doing something, almost being done, then parents come in and don't let you finish.
Yes, I had a rough childhood." - devdevil

You need to log in before commenting.

League of Legends Champions:

Teamfight Tactics Guide