This post has now been superseded by Dental photography 101 – a detailed guide to dental photography. I would highly recommend you check it out.
So you have finally plucked up the courage to twist the mode dial to manual and you are greeted with this horrific picture…
Gulp! Before you change the mode dial back to the happy green automatic mode let us explore what the first line of means. The key ingredients to produce a correct photographic exposure is light and time (Just like a dental radiography). These two variables are controlled by not only the aperture and shutter speed but also the sensitivity of the image sensor ISO and the strength of the flash. Giving the image sensor too much light or time will lead to overexposure.
And of course underexposure occurs when the image sensor receives not enough light or time.
For months I struggled with exposure on my DSLR. My images were either too dark or too light, too grainy or too blurry. I had bought a shiny new camera only to get worse photos then I would from my 5 mega pixel camera on my iphone 4! I now realize that exposing photos for dental photography is all about balance and once you have found that equilibrium you will be taking great photos day in day out.
1) Shutter speed
Shutter speed is the length of time that the shutter curtain is opened for. This allows light to pass onto the image sensor producing a photograph. The shorter the shutter speed, less light will be able to pass through to the image sensor. In macro photography (dental photography) this has one main advantage decreased blurriness because less subject and camera movement will be recorded. Most dentists find the best results with 1/250 seconds.
2) Apertures and F stops
Imagine aperture as a window. The bigger the window the more light that will reach the image sensor. The size of the window is measured in f stop numbers. As f stop numbers increase the size of the window decreases letting less light in. Before you go away thinking that small apertures are bad, there is another variable to bear in mind… Depth of field. Smaller apertures have deeper depth of field (For a full explanation why click this link). This is best demonstrated by the following pictures.
Take a look at the green pencil on the upper picture and then the lower. In the lower picture the green pencil is much crisper as it has been shot with a smaller aperture of f/32 whereas the upper picture has been taken with a larger aperture of f/11. Most dentists will find the best results with an aperture of f/32
3) ISO and sensitivity
The final component of an exposure is the sensitivity of the image receptor or ISO. ISO stands for “International Standards Organisation” which was the governing body that created the standard for film sensitivity. ISO 100 is the baseline speed, ISO 200 is twice as sensitive as 100 and ISO 400 is twice as sensitive as 200… you get the gist. The difficulty with higher ISO is that you get more noise, with randomly colored pixels showing on your photo. Stick to ISO 100 for great photography.
So going back to the starting picture. I hope that you can now tell me what the top line of manual mode now means. Which one is Aperture? Shutter speed? ISO?
I will tell you a secret. Almost all intra-oral dental photography can be taken using these settings shown above. If you do not want to think too hard about your photography copy and paste and voila beautiful photos of teeth. Happy snapping!