Chris's crash course in Exposure

I wrote these notes for a friend some years back, whilst tidying up a few things I found it again and thought it might be best as a blog entry.  So forgive me if this all seems familiar.

Shutter speed

Shutter speeds are shown as fractions.  Until the go over a second, then they are shown with " after them.
So 500 means 1/500^th of a second and 2" means 2 seconds.

Aperture

Aperture is the size of hole you are shooting through, it is recorded as a fraction.
So f2.8 will be a big hole or "wide open" and f/22 is a tiny little hole. Aperture controls depth of field - f2.8 is not much, f/22 is loads.
When you view through a lens normally you are seeing it wide open. The depth of field preview button allows you to see what it looks like at your chose aperture.

Depth of Field (DOF)

Depth of Field is the amount of the picture that is in focus (which is affected by aperture as previously mentioned). Also the longer the lens the less dof you have available, but don't worry about it to much its easier to see than explain.

A Shallow depth of field means the poppy is in focus

but the rest of the field is blurred.

When to use a tripod?

The rule of thumb for hand-holding shots is that the shutter speed should be no slower than 1 over the focal length.
So if you have an 18-55mm lens at the wide end (18mm) you can handhold as slow as 1/20^th of a second, but at the long end (55mm) you should chose 1/55 of a second or slower. Image stabilisation allows you to go 1 or 2 stops slower.
With good technique you should be able to shoot at slower speeds than the rule, but how much slower is something to experiment with and learn for yourself.

What’s a stop?

If you put the camera in AV mode you will see that you can change the aperture in stages E.G. f/11 to f/16 to f/22 each of these stages is known as a “stop” the same applies to shutter speed. As shutter speed and aperture are intimately related changing one will change the other.

So what's that mean in practice?

• A. If you want to take a landscape shot and you want to get everything in focus then you need an aperture of f/8,f/11 or above. So you set the camera to Av (aperture priority) and set it to f/11. Take a look at the shutter speed. Can you handhold it or do you need a tripod? If you want a longer exposure (for blurry water type effects) then set a smaller aperture (higher number).
• B. If you are shooting a single figure in poor light and you would like a blurry background then pick a low f number (f/4 or similar) then check your shutter speed to see if you can hand hold it.
• C. If you are using a tripod there is less to worry about, so you just adjust the aperture for the dof you want, or adjust the shutter speed for any blurring you want.

Understanding Exposure - highly recommended as further reading.

What about ISO?

ISO also moves in stops, so 100-200 is one stop 200-400 another. Increasing the ISO will reduce the shutter speed. You don’t get something for nothing though; increasing the ISO adds digital noise to the image (100 is virtually noiseless whereas 1600 has loads of noise). Though many modern cameras are virtually noiseless up to 400 ISO.

Why would I change the ISO?

So you are hand holding, you have the lens wide open but the shutter speed is still showing as 1/25^th, which is way too slow for your lens. If you increase the ISO from 100 to 400 you get 2 stops back which changes the shutter speed from 1/25^th to 1/100^th and now you can hand hold again….that’s magic!

Further reading

A Beginner's Guide to Aperture and Depth of Field

Adrian Oakes is photographer of the month for February

I have recently been enjoying some lovely images of the snow on Adrian Oakes website, there are some stunning images on there so why not take a look yourself and see what I'm on about.

Alone in the Snow

by Adrian Oakes

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Previous  Photographers of the Month

How to add a Google map to your photography site

I recently (well not that recently, but I'm just catching up with a lot of things), received an email asking how I had got Google Maps on my websites. The maps I am talking about are like this one on Images Of Essex and this at Images of Suffolk.

Step 1 - Create the Galleries

The first thing you need to do is to actually create the galleries you will be linking your map to.
Fortunately both websites are Foliopic sites.  Foliopic have a great system where you can keyword your images and search for the image, the URL for this search can then be used as a gallery.

For example keywording all our images and issuing a search for Orford gives this search: http://www.imagesofsuffolk.com/search/gallery/orford which can be used as an Orford gallery.
Other hosting sites may have a similar system, or you will just have to create galleries for each area

Step 2 - Create The Map

I used  http://mapmaker.donkeymagic.co.uk/ to automatically generate the API code for me.  It is worth registering with the site as this allows you to save maps and you will be coming back to this time & time again as you add new points to the map.

To add galleries, pick a point on the map then give it a name so you can change it later if you need to.

In the code box paste in something like:

<b><a href="http://www.imagesofsuffolk.com/search/gallery/orford"><b>Orford </b>Gallery</a></b>


and change
http://www.imagesofsuffolk.com/search/gallery/orford
to the url for your gallery and Orford to the name of the gallery

Repeat the above process for each gallery then save the map.

Step 3 Get your own api key:

To use Google maps you need to have your own API key.  This is simple enough, go to http://www.google.com/apis/maps/signup.html to sign up and then copy the key.

In Mapmaker click the Get Javascript button then paste your Google Api key in here

<!-- //Change the following line to use your own key available from http://www.google.com/apis/maps/signup.html -->


<script src="http://maps.google.com/maps?file=api&v=2&key=ABQIAAAARKYMX3qABRwgBGTOLfvdgBT2yXp_ZAY8_ufC3CFXhHIE1NvwkxTmhS_LQj6knfNR9GOtLZ_JFxncNQ" type="text/javascript"></script>

Now you can copy all the javascript ready to paste it onto your site.

Step 4 Create a new page

These instructions are specific to Foliopic
Create a new page and click on the source button so you can see the HTML that makes up the page.
Delete all the HTML that is there currently and paste in the HTML from mapmaker.

Remove this block from the top:


<div style="background-color: #fff2cc;">
&amp;title&gt;Simple Google map&lt;/title&gt;


And this from the bottom


<style type="text/css">
div#popup {
background:#EFEFEF;
border:1px solid #999999;
margin:0px;
padding:7px;
width:270px;
}

</style>
</head>
<body>
<div id="map" style="width:600px;height:450px"></div>
</body>
</html>

Step 5 - Styling your map:

Add the following to your css file.


/************** MAP *******************/
#popup {
background:#EFEFEF;
border:1px solid #999999;
margin:0px;
padding:7px;
width:270px;
}

#popup a
{
color:black;
}

#popup a:hover
{
color:black;
}


Any Bristol / Bath Photographers out there?

The Welshot Imaging Photographic Academy seem to be going from strength to strength and are now expanding into the Bristol Area from their heartland in Welsh Wales.

The sheer energy and drive that Welshot put into everything they do is bound to make this new venture a success. If you are in the area it will be well worth your time to check them out.

And now for the slick promo video:

2010 Portfolio Updated

It's not been a great winter for me so far, when the weather has been great for photography I have been unwell and when I have been well the light has been as flat as a pancake.  So instead its time to get round to doing all those admin jobs that are real easy to put off when something more interesting comes up like keywording, cataloguing and updating my web galleries.

The 2010 Gallery includes images from across England and I hope you find something there you enjoy looking at.

Coniston Sunset

Images of Essex Exhibition Timelapse Video

Dave Peck cunningly shot a time-lapse video of us all hanging our latest exhibition at Loughton Library.  The video was shot on a Canon 7D which was taking one shot every 5 seconds.

Images of Essex Exhibition opens in Loughton

Mist in the Woods

The Images of Essex teams latest exhibition opens today at Loughton Library.  Imaginatively called "Images of Essex" it features work from across the county by Dave Peck, Kevin Goodchild and myself. The exhibition runs until the 4th of February and even if I say so myself it is well worth a visit:

Images of Essex - an exhibition by www.ImagesOfEssex.co.uk
Traps Hill
Loughton
Essex IG10 1HD

Telephone: 020 8502 0181

Opening Times:
Monday: 9.00 - 7.00
Tuesday: 9.00 - 7.00
Wednesday: 9.00 - 7.00
Thursday: 9.00 - 7.00
Friday: 9.00 - 7.00
Saturday: 9.30 - 5.30
Sunday: 11.00 - 3.00

If you are in the area please pop in for a view and why not post your reaction here.