Metering mode on a canon dslr camera with examples.

Metering is a process in which a dslr camera measures the amount of light entering the camera depending on the sensitivity of the sensor (ISO). Once the light is measured, it informs the user to adjust either shutter speed or aperture to get a properly exposed image. Older cameras never had a lightmeter preview, so an external light meter was a necessity. The same external light meter logic applied to film cameras as well. 

In this age of dslr cameras, there are few quirks about various metering modes available in almost all of the brands. A metering mode is a way for camera to determine the correct exposure settings. Your dslr then tells you to adjust the settings, so that the meter needle sticks to zero. This can be achieved by changing the shutter speed, aperture or ISO settings. Let's see how does metering mode works with examples. 4 images below are taken from a kit lens using Canon 40D dslr with same shutter speed, ISO and aperture settings. All of them are exactly similar which is expected as no setting was changed except the metering mode dial. 
Evaluative, Partial, Spot, Center weighted average. 

F5.6, 1/25 second, 100 ISO. Evaluative

F5.6, 1/25 second, 100 ISO. Partial

F5.6, 1/25 second, 100 ISO. Spot

F5.6, 1/25 second, 100 ISO. Center weighted average

Above 4 images clearly explain that the image exposure would not change just by changing the metering mode dial, settings need to be varied. Look at the 4 images below now, exposure settings were changed for every mode in order to keep the metering needle at center. In all of the images, same spot was used to focus using center cross point. Here are the settings for individual shots:
1) F5.6, 1/25 second. 100 ISO. Evaluative
2) F5.6, 1/20 seconds. 100 ISO. Partial.
3) F5.6, 1/15 seconds. 100 ISO. Spot. 
4) F5.6, 1/20 seconds. 100 ISO. Center weighted average. 

F5.6, 1/25 second, 100 ISO. Evaluative

F5.6, 1/20 second, 100 ISO. Partial

F5.6, 1/15 second, 100 ISO. Spot metering

F5.6, 1/25 second, 100 ISO. Center weighted average

My personal favourite out of the above 4 would be first image, for the fact that it has somewhat properly exposed background. 
How does it work?
As soon as the in camera meter is balanced (any mode), the metered area records at 18% gray tone of a gray card. Under normal circumstances, metering would yield the expected results. Most commonly used or default option: Evaluative metering mode (matrix in Nikon). 
Evaluative/Matrix: Takes the whole scene into consideration. Works for 90% of the cases, will make another post on where it fails and the possible workarounds. 
Spot metering: Only considers the AF point exposure which is roughly 2-3 % of the total scenery. Let's say you focus on the subject's forehead while taking portraits, spot metering will ignore the background ( Example: Sun) in this case and expose for the forehead only. This mode is also good for taking pictures of moon as explained in my previous post on how to take pictures of moon using a dslr
Partial: Quite similar to spot metering except for the fact that it takes into consideration approx 6% of the total scenery. 
Center weighted average: Extra focus on the center while ignoring the corners. It does take into account 75% of the scene.  

Be a DSLR Ninja. 

How to photograph the moon using dslr?

I learn something new every time I go out with my dslr camera to do photography. An ultra wide angle lens is a part of my gear now, and I have experimented a lot with it in last couple of days. The motivation behind this post is my most recent work doing night photography including moon and stars. It required a fair amount of dabbling with camera settings and post production work too. If you have ever wondered on how to take pictures of our planet's natural satellite, this post will walk you through each and every step. Let's get started.

Equipment required:
Telephoto lens. 
Sturdy tripod. 
Any APS-C or full frame dslr camera. You don't need a fancy full frame or high fps camera. 

Camera settings: 

Manual Focus.
Spot metering.
White balance: Auto if shooting RAW.
Aperture: Somewhere between f8- f12.
Bracketing: Not necessary though, but you can take 3-4 different shots by varying shutter speed. 

1) Attach the telephoto lens to your dslr and turn the power on. 
2) Set up your dslr on a stable surface using a really sturdy tripod. 
3) Point it to the moon and zoom your lens to its maximum focal length. Look through viewfinder if you can see the moon.
4) Turn on live view and magnify 10x times. 
5) In manual focus mode, try to adjust focus on the moon by rotating the focus ring on lens. This takes a lot of patience as the camera shake is really strong since we are zoomed all the way in.
7) Once focus is set up, adjust the shutter speed for proper exposure. I am happy with single shot for now, but you can try 3-4 bracketed shots as well. 
8) Take a picture of some other interesting subject such as highway light trails, a person or a tree to act as foreground. This would add so much more interest to the photograph and make it stand out a lot. For me, I took an image of highway using wide angle lens with exposure time of 30 seconds. 

After photography work: Import both the images in ACDSee Ultimate 10, Adobe Photoshop, or any other layer editor. Combine the image from step 7 and step 8. I would love to show my post production workflow, but it will make this post too long. Stay tuned, will do another post soon. 

Here is what my final image looks like after merging two images:

79% moon during night
F11, 100 ISO 30 seconds.
F11, 100 ISO, 1/80 seconds for moon.

Be a DSLR Ninja.

How does flash exposure compensation works in a dslr camera?

When doing photography in a dark environment with dslr camera in auto mode, the pop up flash gets activated automatically. This is because the brain of camera thinks it is too dark, and requests help from pop up flash to throw in some light. Most of the entry and mid level dslr photography cameras have an on board flash system from the manufacturer itself. Example: Canon Rebel series, 20D, 30D, 40D, etc.
FEC(Flash exposure compensation) is the ability to adjust output power level of a dslr flash unit. The need for flash exposure compensation is due to the fact that the internal flash can cast really harsh shadows or can even lead to an over exposed subject. The adjustment of power level allows a better control over the lightning which leads to properly exposed subject. 
For most of the canon dslr cameras, flash exposure compensation value can only be changed in manual, program, aperture priority, and shutter priority modes.  The images below were photographed in a totally dark room with the external Yongnuo flash unit as the subject.

Image 1: FEC -2
Image 2: FEC Zero
Image 3: FEC +2

Decreased exposure compensation in flash

Flash exposure compensation 0
FEC Zero

FEC +2
The impact of changing flash exposure compensation is clearly visible in above 3 images. Image 3 has the highest value of flash exposure compensation, and that's why it is the brightest.

Use: This flash exposure compensation technique can be used to assist in filling shadows for outdoor portrait photography. Another use can be for indoor events. Increase the exposure compensation and use a bounce card or cover to reflect it from the ceiling. This would light up the whole area with a very pleasing light. Bouncing flash prevents harsh reflections and over exposed edges while doing indoor photography. 

Pro Tip: Camera retains the flash exposure compensation values even after switch off, restart. Let's say you finished a photography session with fec+2 and switched off the dslr, keep in mind that this value would be retained next time whenever a photograph is taken. 

Be a DSLR Ninja. 

Neutral density filter (ND) naming and optical density

If you are thinking to invest in a decent filter system to include in your photography gear, I am sure the nomenclature might have baffled you a bit. I got lucky to be able to borrow a few grad filters from my friend who is a professional wedding photographer. This allowed me to fiddle around a bit with different level of optical density and thus served as the photography inspiration behind this post. The naming of the neutral density filters ( either gradual or non gradual) is like a photography myth, but this short and sweet post will make it easy for you. Some filter manufacturers name them as per optical density of filter while others focus on f-stop number.
Table below relates optical density, filter factor and f stop number for neutral density filters.

Optical density of filter:
0.3     0.6     0.9     1.2     1.5     1.8     2.1      2.4     2.7     3.0  
Filter factor:
2         4        8        16      32     64     128     256    512    1024
F stop:
1         2        3         4        5       6        7         8         9      10

Example: 0.9 ND filter. This means it is a 3 f stop ND filter. Similarly, a 10 f stop ND filter would have an optical density of 3.0. 

So we have got the basic of density filters, but what's the main motive behind spending money on density filters. There are certain aspects of photography which require a use of ND filter. As an example: 

1) Outdoor portrait photography: Neutral density filters help for outdoor portraits in broad daylight. Example: Sun is behind your model or subject. In this case a balance between ambient light and subject exposure can be achieved by using a fill flash and ND filter. Fill flash will prevent shadows on subject face and pop out the subject more. Other way can be exposing for the background which would require a very high shutter speed and great flash power. For detailed explanation, see the last post on High Speed Sync.

2) Landscape photography. Shooting in harsh daylight sun can be made possible by using ND filters of higher optical density. Capturing sunset over the beach using ND filter gives a nice and silky effect to waves and leads to properly exposed sky. ND filter actually allows a longer exposure as it minimizes the amount of incoming light. 

Pro Tip: If you find it hard to focus after attaching filter, focus before on a point (either manually or auto) and then switch your lens to manual mode. Slide the filter in front of your lens and boom. There is a huge debate of using screw on density filters vs square shaped filters which require a holder system such as Lee SW150. 

Be a DSLR Ninja. 

How to decide between TTL and manual mode for external flash photography?

My recent love for doing dslr photography using external flash has made me do a lot of experiments in past 2 weeks. In the previous post we talked about how does HSS and TTL mode impacts the output of dslr flash and ultimately the image exposure when doing photography. This post will summarize what mode of operation to prefer when doing photography based on your subject, lighting, etc. 
The mode of operation of an external flash in photography is classifies into two main types:
1) TTL 
2) Manual
TTL: Through the lens. Canon dslr models have E-TTL whereas Nikon ones have i-TTL for the same mode.
When to use: Indoor photography with rapidly changing lights, fast movement, changing angles, distance variation from subject,etc. are some major factors where ettl comes to rescue. It is not convenient to adjust the flash power every time in order to take a shot just because lighting changed. What would happen? The shot that you wanted to take might be gone by the time power is adjusted. If you are going to change aperture or shutter speed as well, try to stick with TTL. I usually like to keep TTL flash on my camera hot-shoe. 
Bad side: TTL uses 2 flashes, one for metering and other one for actual shot. This makes it really heavy on power consumption. Be sure to carry an extra pack of batteries. 

Manual: Like the word itself says, this mode involves setting the power manually. 
When to use: Outdoor portraits, studio portraits, off camera flash. This mode of external flash operation works really well when a user has full control over the subject and lighting. Example: Portrait photography. 
Bad: For me, the only inconvenient thing was multiple physical movements required to adjust power. 

Pro tip: 
1) Variation of f-stop in dslr photography controls flash exposure, whereas shutter speed controls ambient light.
2) The manual changing of flash power and zoom level can be done by using optical or radio based triggering. 

Be a DSLR Ninja. 

How does E-TTL and HSS impact exposure in a dslr camera?

I bought my first dslr camera external flash (Yongnuo 568 EXII) long time ago, but didn't even touch it as I mostly do landscape and city architecture photography. Adding a small amount of light on your subject during night photography makes it look more interesting, but I wanted to try something different. Example: Outdoor portrait photography.

I am writing this post about my recent experience trying outdoor portraits with a dslr for the first time. One of my close friend agreed for being the test subject for daylight portrait photography. I watched a lot of videos about High speed sync, TTL mode and outdoor portrait photography posing techniques, but was still nervous about the friendly photography shoot.

My flash, lens, camera were working fine on the day of shoot, it was me who wasn't able to judge the harsh late afternoon lightning which definitely led to embarrassment. Shooting RAW format definitely helped, but I still wasn't satisfied with the results. I wanted to practice more and see how my on camera external flash behaves on using HSS( High Speed Sync) and E-TTL mode. As a total beginner with external flash based photography, I learned quite a few really important things in past couple of days.

High Speed Sync: Allows you to exceed shutter speed when an external flash is connected to your camera. The default max value is 1/200 or 1/250 in most canon cameras. You can check this maximum by connecting an external flash physically to your camera and rotating the shutter speed dial.Why high speed sync? Well,  high speed sync is an extremely important feature for outdoor portrait photography. When taking a portrait against brightly lit and distracting background, it is good to have a shallow depth of field. This means the f stop value should be on the lower side like 1.2, 1.4, 1.8, 2.0, 2.8, etc. This opens up the aperture and more light starts to reach sensor when a picture is taken. In order to balance the amount of light, high shutter speed is required otherwise the background would appear to be blown out. The role of external flash is to illuminate your subject and maintain a proper exposure during photo shoots.

E-TTL vs Manual Flash: Let's talk about canon cameras. E-TTL (Through the lens) is like an automatic adjustment of flash power as soon as shutter is pressed. If the aperture or shutter speed value is varied, the flash power is adjusted in order to keep the subject properly exposed. The required power level is determined with a pre flash. There is a pre-flash but it won't be visible easily. Change your external flash settings to second curtain and lower shutter speed like 1 or 2 seconds. You will see two different light flash now. The first one determines the exposure and second one is the primary light hitting the sensor.
Here are a few sample pics:
1) E-TTL
F5.6, Same focal point. ISO 100

dslr photogtraphy in E-TTL mode
E-TTL mode: 1/10 Shutter speed
dslr photograph in ettl mode
E-TTL mode: 1/100 Shutter speed

dslr photograph in e-ttl mode
E-TTL mode: 1/250 Shutter speed

dslr photograph in e-ttl mode
E-TTL mode: 1/800 Shutter speed
TTL means through the lens. The pre flash reflected from subject goes through the lens and determines the final power output. In order to take the last photograph, high speed sync on Yongnuo 568EXII was involved as the max sync speed on my Canon 40D is 1/250 seconds. From above 4 example images, it is really clear that flash output is trying to maintain constant exposure of the subject.

2) Manual
Same  F5.6, focal point and ISO.

dslr photograph in manual mode
Manual mode flash: 1/100 second
dslr photograph in manual flash mode
Manual mode flash: 1/250 second

dslr photograph in manual flash mode
Manual mode flash: 1/500 second

dslr photograph in manual flash mode
Manual mode flash: 1/1600 second
Manual mode means the photographer or user takes control of the power. In other words, manually adjusting power level every time more or less light is needed. Let's set the flash to a full power level i.e. 1/1. Other options are 1/4/. 1/16. 1/32, 1/64, 1/128.In order to take the last two images, had to turn on the high speed sync on 568EXII. It is easily noticeable that the exposure of subject varies with shutter speed. Every time a picture is taken, same intensity level flash is fired.

Summarizing, outdoor portraits need high speed sync when using a fill flash and higher intensity of flash power as well. Exposure starts to go down because of less light availability as explained in the previous post about impact of shutter speed on light. Distance between subject and photographer or dslr camera also matters when doing high speed sync portrait photography.
These two points were lacking in my first outdoor portrait photography shoot, but I will do it again soon with a better level of experience gained from my mistake.

Be a DSLR Ninja.