Did you get it right? It seems most of you did, with 90% of entries choosing the right answer.

The question was "What does a histogram tell you about an image?"

The answer clearly being: "The tonal range and distribution within the image"

For those fw who didn't get it right, and those that didn't answer because they weren't sure, here's a quick recap of histograms. 

A histogram is a graph. If you think of it as a bar chart, it becomes much easier to understand. There are two axes - the X and Y axis (or for non-technical people, the horizonalt and vertical axis!)

The horizontal axis along the bottom is the tonal value. That is a measure of brightness, with black being on the left and white being on the right. Mid-tone gray is in the middle surprisingly! 

The vertical axis equates to the number of pixels, with no pixels being at the bottom. 

With this information we can see that as you move along the horizontal axis there is a bar at each tone. The height of this bar tells you how many pixels there are at that brightness level.  In itself, the histogram can't tell you if you've got your exposure correct, however, with your knowledge as well, it can. 

There is no such thing as the 'perfect' histogram. It doesn't exist. Even if it did exist, it certainly wouldn't be a bell shape curve with the highest peak in the middle - well, not unless you photographed something with an even arrangement of tones across the scene, but with most in the mid-tones! 

If you photograph a scene that is predominently bright or white, you would expect the histogram to be pretty much totally up to the right hand side. The opposite is true for dark subjects. 

The other common mis-understanding about histograms is that you should avoid the bars reaching the top of the vertical axis. ell, the truth is it doesn't matter. It simply means there are a lot of pixels at that particular brightness value and the scale used on the vertical axis can't show them all. It means nothing about the overall exposure. 

The axis you do need to watch out for though is the horizontal one. If you have bars hitting the left or right, you will be blocking shadows or blowing highlights. Again though, this is not the end of the world. Take for example the image above. The histogram is all the way over to the right and there are blown highlights. However, it was a consious decision. Had I pulled the exposure down to avoid blowing those highlights, the front of the subject would have been too dark and the picture would not be as good. So while it's true that generally you want to avoid radically over or underexposing, there are situations where the better picture is had if you do over-expose parts of the scene. 

Now, most of you are at least enthusiast photographers - right? So surely you understand exposure - right?

Well jusdgin by the low number of entries we've so far had for the exposure quiz, either you're not sure you know the answer, or you don't have the spare 2minutes time to work it out. 

Whether it's the former or the latter, here's a little hint that will help you figure it out: Everything is measured in 1/3rd stops - Shutter Speed, Aperture and ISO. So, if one setting moves in one direction, one of the others has to move in the opposite direction by the same number of steps to keep the exposure the same. So, all you need to do is set the starting exposure on the camera and then adjust each of the the paramaters to the new setting and work out how many steps it was. So if shutter speed moves +6 steps and aperture moves -3 steps and ISO moves -3 steps, the exposure would be equal and your picture will capture the same amount of light. 

So what are you waiting for? Come and and have a go...it's only just on the right hand side of this post!

It's amazing to think that the EOS 5D Mark II is still making waves like a tsunami this long after launch, but that's really because it is just a very capable camera.

We've talked about the movie mode quite a lot, but looking back through the posts, there's something we haven't mentioned and it might just trip you up...

If you want to get manual movie exposure, you need to put the camera into M mode. Seems logical enough. However, there is a stumbling block - in the Live View/Movie mode settings, you need to make sure you select: Still+movie --> Movie display. If you choose Stills+movie --> exposure simulation, then even in Manual shooting mode, the camera will carry out the exposure adjustments for movies. 

It's one of those quirks that could trip you up if you're not looking for it.  So now you know!