In answer to Christines question....

Greetings,

Thank you all for your kind comments on the last entry, one of those comments from 'Christine' asked a question about HDR (High Dynamic Range) and so I will try to answer it in my usual rambling way...

"Christine said...

I love this blog!! After reading this last post, and can I say the portraits are stunning, I have enrolled on a basic camera skills night school course. Thank you.

If you have time can you explain "HDR" in terms I can understand? It appears a lot on photo websites and my iPhone even has a HDR function but no instructions as to how to use it! All I know is that the images in HDR seem to have a surreal quality to them.

Thanks in advance, and please keep your entertaining and informative blog alive an kicking.

Regards Christine "

Right,

Dynamic Range refers to the amount of contrast (light and shadow) detail we can see in a single image, so "High" Dynamic range refers to images where we can see a bigger range of detail in shadows and highlights....

The human eye is an amazing piece of kit, when we look at something we can see all the details in the shadows and all the details in the brightly lit bits at the same time. This is due to the awesome design of the eye itself and also the fact that our Iris (pupil) and brain are working to continually adjust to the conditions and fill in the details. All this happens so fast that we just see a complete correctly exposed and detailed image.

Ooooooh, before I go on I must mention 'Exposure' (the amount of light the eye/lens/film/sensor is exposed to)... So, we see things because of light being reflected back into our eye yes? Well exposure is just how much of that light we let in, and this is controlled by the iris (pupil) opening and closing to either let in more or less light. A camera is the same, we control the exposure by adjusting the lens aperture (an iris within the lens), or the amount of time we let the light in for (shutter speed). If something is too bright we can say too much light is being let in (over exposed), if its too dark then we are not letting enough light in (under exposed) and when it s just right we can say it is correctly exposed.....

So we agree that the eye is awesome and can see a huge range of detail in shadows and highlights at the same time....

Now lets apply that to a camera. Unfortunately the camera can not see such a massive range of contrast at the same time (The Dynamic Range is not as big). As a rule we have to, as photographers, when taking a picture of a high contrast (Very dark and very bright bits at the same time) scene, pick our settings so that the most important part of the picture is correctly exposed, knowing that we will lose detail in other parts of the picture which fall outside of the cameras range. Eg:





The majority of the picture is correctly exposed, but we have lost details in the areas I have circled where the camera cannot record the detail as it falls outside of its dynamic range.

The other extremes would be to set our exposure to record just the highlights or just the shadows like in these next two pictures (I have this time circled the areas I want to be correctly exposed in green)






So we now have three images with different correctly exposed parts and that's where High Dynamic Range comes in. Its either a piece of software on the computer or built into your camera that allows these three (or more) images to be brought together in one balanced image. Where we can see details in the highlights and the shadows all at the same time.

The result looks something like this when it comes out of the processing stage.....



You can see that the whole image is fairly well exposed, from the shadows to the highlights, with details within all of those parts.... It does however look a bit "painterly". This is because when we look at this scene in real life we can see the brightness and the shadow and everything in between, but the HDR processing darkens the bright bits, lightens the dark bits and messes about with the bits in the middle... what we are left with is not actually a high range, but the same range with Highlights and shadows adjusted to fit in with it.

If you are processing an HDR image on the computer with a program like Photomatix you can play with different levels off effect, to make the image appear more natural or even a psychedelic grungy mess, its very easy to over process as even the lightest processing still has a slightly painterly quality to it.

So that's basically HDR in a nutshell, I'm sure the purists among you will notice that I have over simplified this a great deal and missed out a lot of technical crap. That was my intention, if you want to read about differential light pattern encoders and reflected luminescent prismatic correction I will be happy to discuss it with you at www.don't_be _so_frikkin_dull_and_get_out_and_take_photos.com (<that's a joke).

Thanks for reading half of this then getting bored and having a sandwich.

Here's a picture of a blackbird that pissed me off by sitting outside my window and singing at 5 am this morning!!!!!



Until next time.... Byeeeeeee
(p.s. Leave comments or you will grow a boil on your bum!)