Archive for September, 2010

The Exposure Triangle

Posted: September 21, 2010 in Photography

As I stated in my post “Understanding White Balance”, photography is all about light. Each of the three aspects of the triangle relate to light and how it enters and interacts with the camera. The 3 aspects of the triangle are;

ISO – the measure of a digital camera sensor’s sensitivity to light.

Aperture – the size of the opening in the lens when a picture is taken.

Shutter Speed – the amount of time the shutter is open.

It is at the intersection of these 3 elements that an image’s exposure is worked out. Most importantly, a change in one of the elements will impact the others. In other words, you can never really isolate one without affecting the others.

ISO

ISO is measured in numbers (100, 200, 400, 800, 1600, etc.).  My Nikon goes 200, 400, 800,1600, and HI1. HI1 is actually 3200, and no, I have no idea why they didn’t just call it 3200. The lower the number the less sensitive your camera is to light and the finer the grain. Higher ISO numbers are usually used in darker situations to get faster shutter speeds. One thing to keep in mind with higher ISO is it creates ‘digital noise’.  Instead of having a flat black, it is now more of a dark grey with specs, or pixels, of assorted other colors.

100 ISO is accepted as ‘normal’ and will give you tack sharp pictures in situations where the lighting is good.

When you do override your camera and choose a specific ISO you’ll notice that it impacts the aperture and shutter speed needed for a well exposed shot. For example – if you bumped your ISO up from 100 to 400 you’ll notice that you can shoot at higher shutter speeds and/or smaller apertures.
When selecting the proper ISO setting, ask yourself these 4 questions;
  1. Is the subject well lit?
  2. Do I want a grainy shot or one without noise?
  3. Am I using a tripod?
  4. Is the subject moving or stationary?

If there is plenty of light, I want little grain, I’m using a tripod and my subject is stationary I will generally use a pretty low ISO rating.

However if it’s dark, I purposely want grain, I don’t have a tripod and/or my subject is moving I might consider increasing the ISO as it will enable me to shoot with a faster shutter speed and still expose the shot well.

Of course the trade off of this increase in ISO will be noisier shots.

Situations where you might need to push ISO to higher settings include:

  • Indoor Sports Events – where your subject is moving fast yet you may have limited light available.
  • Concerts – also low in light and often ‘no-flash’ zones
  • Art Galleries, Churches etc- many galleries have rules against using a flash and of course being indoors are not well lit.
  • Birthday Parties – blowing out the candles in a dark room can give you a nice moody shot which would be ruined by a bright flash. Increasing the ISO can help capture the scene.
Here are some shots I took using different ISO settings. First set of 5 is from outdoors, full sunlight.
Indoor shots with no lights on.
Notice the noise in the last shot, especially on the red wall. Click images for full size.
Aperture
Aperture refers to the amount of light that falls onto the sensor.
Just like successive shutter speeds, successive apertures halve the amount of incoming light.  To do this, the diaphragm reduces the aperture diameter by a factor of 1.4 so that the aperture surface is halved each successive step.
Apertures are listed in terms of f-numbers (expresses the diameter of the entrance pupil in terms of the effective focal length of the lens; It is the quantitative measure of lens speed), which are marked on the lens.  On a camera, the f-number is usually adjusted in f-stops.
Each “stop” is marked with its corresponding f-number, and represents a halving of the light intensity from the previous stop. Modern electronically-controlled interchangeable lenses, such as those from Canon and Sigma for SLR cameras, have f-stops specified internally in 1/8-stop increments, so the cameras’ 1/3-stop settings are approximated by the nearest 1/8-stop setting in the lens. The F number can be displayed as 1:X instead of f/X
Lenses with larger apertures are faster because, for a given ISO speed, the shutter speed can be made faster for the same exposure. A smaller aperture means that objects can be in focus over a wider range of distance (depth of field).
Portrait and indoor (sports and theater also) photography often requires lenses with large maximum apertures in order to be capable of faster shutter speeds (and narrower depth of fields) in order to combat the low light problems with no camera shake.
The narrow depth of field in a portrait, as well as in macro photography, helps isolate the subject from the background.
Here are some examples of adjusting the aperture for different effects.
Large depth of field
Aperture – f22
Shutter Speed – 1/60 sec
ISO – 400
Focal length – 34mm
Focus – AUTO
Shallow depth of field (focus on subject in front)
Aperture –  f5.3
Shutter Speed – 1/60 sec
ISO – 800
Focal length – 42mm
Focus – Auto
Shallow depth of field (focus on subject in back)
Aperture – f4.0
Shutter Speed – 1/60 sec
ISO – 400
Focal length – 24mm
Focus – Manual
Shutter Speed
Shutter speed is simply the shutter time.   Normally your sensor  sits around in the dark waiting for a bit of action. It is the shutter – like the blinds or curtains which shut light out of your room – which keep the sensor in the dark. When the shutter opens, it lets in light and the sensor gets to work.Exposure time, then, is the time interval or duration during which your camera’s sensor  is collecting light to capture your image.

Shutter speed is measured in seconds – or in most cases fractions of seconds. The bigger the denominator the faster the speed (ie 1/1000 is much faster than 1/30).
In most cases you’ll probably be using shutter speeds of 1/60th of a second or faster. This is because anything slower than this is very difficult to use without getting camera shake. Camera shake is when your camera is moving while the shutter is open and results in blur in your photos.
If you’re using a slow shutter speed (anything slower than 1/60) you will need to either use a tripod or some some type of image stabilization (more and more cameras are coming with this built in).

Shutter speeds available to you on your camera will usually double (approximately) with each setting. As a result you’ll usually have the options for the following shutter speeds – 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8 etc. This ‘doubling’ is handy to keep in mind as aperture settings also double the amount of light that is let in – as a result increasing shutter speed by one stop and decreasing aperture by one stop should give you similar exposure levels (but we’ll talk more about this in a future post).

Some cameras also give you the option for very slow shutter speeds that are not fractions of seconds but are measured in seconds (for example 1 second, 10 seconds, 30 seconds etc). These are used in very low light situations, when you’re going after special effects and/or when you’re trying to capture a lot of movement in a shot). Some cameras also give you the option to shoot in ‘B’ (or ‘Bulb’) mode. Bulb mode lets you keep the shutter open for as long as you hold it down.

When considering what shutter speed to use in an image you should always ask yourself whether anything in your scene is moving and how you’d like to capture that movement. If there is movement in your scene you have the choice of either freezing the movement (so it looks still) or letting the moving object intentionally blur (giving it a sense of movement).

To freeze movement in an image you’ll want to choose a faster shutter speed and to let the movement blur you’ll want to choose a slower shutter speed. The actual speeds you should choose will vary depending upon the speed of the subject in your shot and how much you want it to be blurred.
Focal Length and Shutter Speed – another thing to consider when choosing shutter speed is the focal length of the lens you’re using. Longer focal lengths will accentuate the amount of camera shake you have and so you’ll need to choose a faster shutter speed (unless you have image stabilization in your lens or camera). The ‘rule’ of thumb to use with focal length in non image stabilized situations) is to choose a shutter speed with a denominator that is larger than the focal length of the lens. For example if you have a lens that is 50mm 1/60th is probably ok but if you have a 200mm lens you’ll probably want to shoot at around 1/250.

Here are some shots I took of a ceiling fan using different shutter speeds.

Aperture – f4.5  (yes, the fan is on!)
Shutter Speed – 1/10 sec
ISO – 400
Focal length – 32mm
Focus – Auto
No tripod
Aperture – f2.5
Shutter Speed – 30 sec
ISO – 400
Focal length – 28mm
Focus – Auto
Tripod
Here is the same shot with the same settings, but without using a tripod.
So, there you have it. Pretty much the basics of how to take a great shot. Use this information and practice, practice, practice. Get out your camera manual and see how to change these settings, then start shooting.  If you understand these concepts, you should be shooting ‘gallery ready’ shots in no time.  It is not the camera that takes the great shots, it is the photographer.
Leave a comment, or send me an e-mail if you have questions. Good luck, and enjoy!


Understanding White Balance

Posted: September 19, 2010 in Photography

Photography is all about light. One of the major characteristics of light we depend on in photography is how color is communicated. The human brain is able to detect and compensate for different lighting temperatures. As a result, a white object will look white to the eye, no matter if it is viewed under sunlight, cloudy diffused light, incandescent or fluorescent light.

Every time a digital camera takes a picture, it needs to establish the white point as the basis from which the percentage of each color is derived. Because this is affected by the quality of light in a scene, most cameras offer adjustable white balance settings.

In auto mode, complex algorithms in the camera decide where the white point is. This is usually fairly accurate, though under cloudy conditions it may cause the image to be slightly blue. Incandescent or tungsten setting should be used for pictures indoors without flash. This will adjust the white balance when the subject is lit by light bulbs, such as those in a home.

Use the fluorescent mode when the scene is lit by tube lighting.  As there are several types of fluorescent lighting (cool white or warm white), you may find more than one fluorescent adjustment.

Many digital cameras also offer a manual setting in which the user has to decide what the exact white point is. A rectangular piece of white card can serve as a good reference and you can adjust white balancing by using this. Just point the camera at the white card, filling the frame in the viewfinder, and take a picture.

Below are pictures I took outside on a sunny afternoon. The camera was in ‘Program’ mode, ISO was at 200, manual focus. I used the 7 different white balance modes to show the difference between all modes.

1st Row –  Auto White Balance, Cloudy

2nd Row – Direct Sunlight, Flash

3rd Row – Flourescent, Incandescent

4th Row – Shade

Here are some pictures from indoors. Once again, shot in ‘Program’ mode, ISO was 400, and manual focus.

1st Row – Auto White Balance, Cloudy, Direct Sunlight, Flash

2nd Row – Flourescent, Incandescent, Shade

Lightroom Adjustment Brush Example

Posted: September 16, 2010 in Lightroom

Here is a picture I took a few years ago in Santa Barbara, California. This is just a straight RAW file with no editing in Photoshop or Lightroom converted to a .jpeg.

Here is the same pic with some editing with the adjustment brush in Lightroom. It is ugly and I went to the extreme, but it shows you what you can do with the adjustment brush in Lightroom. Notice the sand is darker, I added a little punch to the waves,  lightened up the water in the front of the wave, and darkened the sky. Click on the pictures to get a full view of the image.

IMHO, the adjustment brush in Adobe Lightroom is by far the coolest tool in the app. If used correctly, it can take your picture from good to great. I have ‘dabbled’ with it, and have gotten pretty good at using it until I saw this video by Dan Moughamian @ Tipsquirrel.

Enjoy.

I found an issue when loading a picture gallery created with Adobe Lightroom 2 to a web server hosted by godaddy. I used the Lightroom default HTML gallery. When I set up my hosting account, I selected a Windows server instead of going with my gut instinct of using a Linux server. Anyway, after the gallery was created, I uploaded the folder to my web server, and the pictures were missing, but the frame of the page existed. I opened the html page in Dreamweaver and checked all the links to make sure the img src in the page was pointing to a .jpg file, then I checked the path to verify that there were images loaded where it said they were loaded at, and they were. I then deleted the folder I just uploaded and used a different web template, this time the Lightroom default Flash gallery with the same result.

I triple checked the index.html page, and ran a check to make sure all links worked, and they did. I then deleted the folder again, and used a different template in Lightroom. This time I used the Airtight Simpleviewer, and it worked. Huh?

I did some research and come to find out godaddy doesn’t support a ‘bin’ folder on a Windows server. I then created 2 galleries, one with the default HTML gallery, and one with the Airtight gallery. Both have a ‘bin’ folder, so what gives? I know that Windows can be a little quirky with stuff like this, so I contacted godaddy and asked if I could switch to a Linux server. They showed me where to go to fix that, and within an hour I had it switched to Linux, and now both galleries show up on my site. Yahoooooo!!!

None of this will make a lick of sense to you if you don’t have Adobe Lightroom, but if you do and you use godaddy as a web host, before creating a gallery, switch over to Linux and save yourself the frustration.

Mystery Solved

Posted: September 13, 2010 in Photography

First day of class down, and I learned something today that I have always wondered. What does that ‘mm’ on a camera lens actually measure? For example, what does 18-55mm actually mean.

When parallel rays of light strike a lens focused at infinity, they converge to a point called the focal point. The focal length of the lens is then defined as the distance from the middle of the lens to its focal point, and that is measured in millimeters. The ‘f/’ number, or ‘f stop’ is a measure of aperture, or light. Aperture is expressed as F-stop, e.g. F2.8 or f/2.8. The smaller the F-stop number (or f/value), the larger the lens opening (aperture). We will get into that and shutter speed next week. Can’t wait!

All in all, a good start. Most of today’s class was basic camera knowledge, which I have a pretty good understanding of. Camera care, storage, memory cards, different types of software, white balance, compression (jpeg and RAW), etc. Good class and good teacher. Looking forward to next week!

Back to School

Posted: September 13, 2010 in Photography

Today is day 1 of school for me, Digital 101. Seems pretty basic stuff, but hoping I can learn some new stuff that I thought I knew. Looks like digital 102 and 103 is where I should be starting after reading the coursework, but I’ll be happy with these baby steps first.  I will share some of the stuff I have learned with others. We will be taking field trips and doing some shooting, so I will post images and hopefully as the class progresses, my shot taking capability improves. Folks are free to critique the images I post. That way I can learn what I am doing wrong, and others will also learn.

I can’t remember the last time I was so eager to start school!