Light- How much light is around us and what does it mean for photography

While deleting some images on my computer, I came across this old image/graph that mentioned typical light intensity for different situations. This can be helpful to know limitation of cameras in low light. If you want to take good photos in low light with your iPad or iPhone and if you are not able to do so, it is not your fault.
In graph below, we are not supposed to remember various numbers but this one does show how dramatically light varies from situation to situation. In outdoor under mid day Sun compared to a bright indoor room, light intensity is 500 times more! When you compare this bright mid day under Sun to an indoor dim room, the light intensity is 6000 times more!

Clear Full Moon light is around .03 Lux. Typical Starlight is around .001 Lux.

So up to 500 Lux, a handheld camera can take good sharp photos IMHO (my guess). However to take good photos in situations with lesser light, we need either a tripod or faster and/or bigger sensor cameras and a stationary

Practical considerations for Light and Exposure in day to day use:

* iPhone 6 has widest aperture of 2.2. Assuming ISO of 400 (beyond 400, images will be grainy) and very stable hands, you can take shutter speed of 1/75 seconds.
With this, the lowest light you will need to take sharp good photos with your iPhone 6 is around 226 Lux. This means in brightly lit homes or in offices to outdoor photos, an iPhone or any latest smartphone camera can be useful.
If you like to use ISO at 100 only, you will need 907 Lux of light intensity.

* On the other extreme, high end full frame SLR with a fast lens of f/1.2 can take good photos even at ISO 3200. Assuming same shutter speed of 1/75 seconds, it can take good photos in light as low as 9 Lux!

If you have a Lux meter, you can use this equation (Lux= Square of F number * 1/shutter speed * (250 /ISO)) for determining the variables like Shutter Speed needed, or ISO needed for a given aperture. The discussion in this post is  mostly to get a feel about what is going on when you press the shutter release button in any camera. In reality, when you press the button, the sensors and computers inside you camera, takes the reading of the light in the frame and uses some equation like above to set up aperture opening, shutter speed and/or ISO depending on the mode. If you shoot in Manual, you provide the numbers and camera stops thinking. If you are in A or Av mode, you tell camera what value to use for aperture. If you have set up ISO too, camera will determine shutter speed based on some equation like the one above.

So ignoring bokeh or image sharpness with faster lens and bigger sensors on DSLR, an iPhone or any smartphone or a fixed lens camera can take good photos in light that is 200 Lux or more. This means well lit indoor or bright outside. With bigger bodies and more investment, you can go down as low as 10 Lux hand-holding your camera which would be Family living room lights, relatively dim indoor, office building hallways or very dark overcast day.

Now with a tripod and if you subject is stationary, you can go and shoot in almost any situation. If you want to shoot stars though, you need only a high end DSLR as if you go beyond exposure of 10-20 seconds, you will capture movement of stars.

Hope this helps.

Sources:
If you want to get into technicality of exposure, here is a nice summary on DPReview chat. Not sure if it is accurate but it mentions that

N^2/t = L*ISO / (10/0.67)

....for ISO = 100, N = 2.8, t = 1/100, and a calibration constant K = 12.5, the required luminance would be about

L = 2.8^2*100*12.5/100 = 98 cd per sq. meter

to produce a middle grey tone in your final image. Illumination is trickier, and a typical calibration constant is 250 for incident light measured in lux. So for this same example we would need

L = 2.8^2*100*250/100 = 1960 lux.

I know LUX is very confusing measure compared to meter or centimeter for length, pound or kg for weight or second/minute for time. Lux measures intensity of light. Instead of getting into technicals of it, I would rather remember relative values so you can understand how it affects photography.

If you want the definition of Lux, here it is from Wikipedia.

"The lux (symbol: lx) is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area.^[1] It is equal to one lumen per square metre. In photometry, this is used as a measure of the intensity, as perceived by the human eye, oflight that hits or passes through a surface. It is analogous to the radiometric unit watts per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception. In English, "lux" is used in both singular and plural.^[2]"

Here are some examples of the illuminance provided under various conditions:(Source: Wikipedia

Examples
Illuminance	Surfaces illuminated by:
0.0001 lux	Moonless, overcast night sky (starlight)[3]
0.002 lux	Moonless clear night sky with airglow[3]
0.27–1.0 lux	Full moon on a clear night[3][4]
3.4 lux	Dark limit of civil twilight under a clear sky[5]
50 lux	Family living room lights (Australia, 1998)[6]
80 lux	Office building hallway/toilet lighting[7][8]
100 lux	Very dark overcast day[3]
320–500 lux	Office lighting[6][9][10][11]
400 lux	Sunrise or sunset on a clear day.
1000 lux	Overcast day;[3] typical TV studio lighting
10000–25000 lux	Full daylight (not direct sun)[3]
32000–100000 lux	Direct sunlight

Better Photos With Any Smartphone Camera

Smartphone cameras are more prevalent and more popular than dedicated cameras these day. There are two main reasons. Most of us have a smartphone with us most of the time and this results in an always-available camera. The second reason is that the smartphone cameras are getting better in capabilities. They generally have respectable 8MP resolution and they do pretty good job for day-to-day photography in good natural light.

As you have noticed, most smartphones are fully automatic in nature. They don’t let you do manual focusing or select aperture, shutter speed or ISO. Thy generally have just one or two controls. They generally let you select Flash. Other than that, there is nothing else you can do.

Advantages of phone cameras:

·         Easy to use.

·         Always Available: We have them with us almost all the time. There is no need to carry an extra gear!

·         Shortest response time: Compared to a typical camera which you have to take out of the bag, turn on, focus and shoot, a phone camera is always on and you can take a photo in a fraction of a moment.

·         Offers Auto-backup: In your traditional camera, your SD card can go bad or can get lost but most camera phones automatically backup photos in cloud storage.

·         HDR and Panorama: Unlike traditional cameras, most smartphone cameras these days offer HDR and Panorama shots. With HDR, you can easily take day light, high-contrast photos with more details than a regular capture. The Panorama offers you to take wide angle shots very conveniently.

·         Wide Angle photos: Most phone cameras are naturally wide angle so you can cover more without needing to change a lens.

·         Macro photography: Smartphone cameras are great for good light macrophotography. No need for a macro lens or changing any settings.

Issues with camera phones:

·         Not many controls available. You can’t do much if you don’t like the shot your camera takes.

·         Tiny sensors and tiny lenses limit your ability in low light or indoors. Many times your photo may look better in iPhone’s retina display or Samsung’s bright LCD screens but viewing them on a standard computer monitor or an HDTV, you will see the issues.

·         If you print camera phone photos, most of them may not look as good as photos taken with a dedicated camera.

·         Flash. Most phone cameras have a flash but I think their flash is more of an issue than an advantage. Their Flash is a tiny LED which most of the time will wash out your subjects in photos.

How to take better photos with a smartphone camera?

1.      For taking photos of the landscapes, turn on HDR and take some phones with HDR too.

2.      Many times for landscapes, use Panorama feature to make your landscape photos look even better.

3.      Enable your phone camera to take photos with touching the screen. This is one powerful way to take better photos with your smartphone. When you touch, camera focuses on that particular subject. This way you can control the focus in your camera. The area you touch also tells camera to expose based on the light in that area. If you touch a dark area in your frame, your smartphone will think that the scene in front of it is dark so it will take in good deal of light. This can result in more details but some parts getting washed out. On the other hand, if you touch some brighter area, the phone will think that the scene is too bright so it will take in less light. This will result in an under-exposed darker photo.

Here is an example. On my hike, I took a photo of Simi Valley, CA in Auto mode (I mean just pressing the Capture- Shutter Release button):

Now if I wanted to get better sky colors, I would need to tell my iPhone to take in less light. To achieve this, I touched the sky in the frame. Here is a photo which captures the sky colors well:


Now if I want to over expose the phone, I would touch the darkest part (most towards the bottom of the frame). Here is a photo with much more light in. It has much more details but the sky is washed out:

If you are reading this article on a bright table or a phone, you may not see the variance in light but on an IPS monitor (or in reality), all 3 photos have different exposure/light. Also, I am not telling you which photo is better here but I am trying to show you that you can control the light intake or exposure with a smartphone camera even though there may be no button there.

Why is my iPhone or iPod not taking good photos?

Many people love their iPod, iPad, iPhone or any smartphone as such, for the nice photos it takes. It is true that in good light and in outdoor bright places, these instruments take nice photos. Also, they have very optimized display so even an okay photo will look bright and nice on any smartphone or on iPod/iPad. However in many situations, iPod or any camera as such will run into its hardware restriction. Because of its sensor's size and size/quality of lens, iPod/any smartphone can't work well in certain lighting situations. However if you are willing to help, you can still have better photos in some situations where your smartphone alone simply fails.

Here are certain things YOU can do to improve your photos in low light:

1) Shoot in good light. Avoid shooting in low light, indoor or in dark places. Outdoor and in well-lit places, your iPod will take nice photos but when light gets low, its tiny sensor and tiny lens can't take in enough light in 1/50 seconds which is required to take nice photos of people or moving objects.
2) In low light or  indoors, if possible, turn on artificial light. If you are in a room, turn on lights or use flash lights. If there is a flash on iPod, use it.
3) If you are shooting stationary items or very slow moving objects, put your iPod on some steady surface (instead of holding in hand) and that can eliminate blur in your photos.
4) Also, you can enhance photos with Picasa or similar software to some extent. There are many such software out there.
5) Not sure what kind of manual controls, iPod offers. If my iPhone5 is any clue, you can't do any thing to control iso, aperture or shutter speed. So except about tips, there isn't much you can do with your iPod.

You might like my blog where I write about such stuff.
http://photography-with-any-camera.blogspot.com/