Experimenting in Cannock Chase Evaluation

I have edited the photos from 17 January 2010 (shot in RAW) and the series of shots do show that changing the f/stop from f/5.6 to f/20 does have an effect on the clarity of focus on the background, something I was hoping to show. The background gets clearer the higher the f/ stop number, i.e. the f/20 shot has a clearer background than the f/5.6 one.

What I wasn't expecting from the photos but is evident in all the shots is that the model isn't in clear focus, but the tree she is leaning against is. I thought that I had focused on the models eyes but aparently not. Focusing is obviously something I will need to work on to improve the quality of my photos, i.e. I need to ensure the subject is sharply focused.

Any comments or advice/tips would be greatly appreciated.

Click HERE to see the photos