White/White, Black/Black. It's all GREY.

So our task for Week 2 was to expose our cameras' propensity for turning things grey. You see the camera doesn't understand exactly what it is you're shooting, and as a result is set to average a scene to 18% grey. This is all to do with metering and exposure, and is why snow scenes are likely to turn out a dull grey instead of a bright white.

The task set was to shoot the following:

1. White object against white background
2. Black object against black background

The first shot was to be taken using aperture priority. Seeing as the scenes were at a fairly uniform brightness I left the metering mode on evaluative (the standard mode).  All shots were taken with AWB (as DS says, when shooting in RAW you can change this in processing later, so keep it simple) at ISO 400.

f/1.8, 1/2500

The picture looks grey because the camera has underexposed the image, having metered the scene and deciding it was too bright based on it's averaging to grey rule. In order to counteract this you need to overexpose the image by 1-2 stops compared to what your camera has decided, so I did this by switching to manual mode and reducing the shutter speed, with the following results:

f/1.8, 1/1250 (+1 stop)

f/1.8, 1/640 (+ 2 stops)

f/1.8, 1/800 (somewhere between +1 & 2 stops)

I felt when reviewing the image on the camera that the +2 stops was slightly overexposed, so I reigned it in a little. But I think the series very clearly shows that the camera's automatic metering doesn't always get it right, so it's important be aware of how it works and what it's limitations are so that you can apply the necessary adjustments to get the right image.

The next series illustrates the same principle but in reverse: when faced with a predominantly black scene the camera will try to average it to grey, and it will do this by overexposing the shot. This time the solution is to underexpose by 1-2 stops.

f/1.8, 1/80 (AP)

f/1.8, 1/160 (-1 stop)

f/1.8, 1/320 (-2 stops)

Just to conclude the correct exposure could also have been achieved by adjusting the aperture or ISO settings.

Let's get RAW!

JPEG from Camera

PNG, converted from RAW file

Ok our first assignment was to take a portrait in natural light. I was lucky that last Sunday I had great lighting in the afternoon and a semi-willing model.

I shot using my Sigma 55-200mm lens on manual (f4.0, 1/1250, AWB, ISO 400).

But anyway the most interesting outcome of this exercise was seeing the difference between shooting in RAW vs JPEG. For the first time ever I shot in both, so I could see what processing the camera was applying to the compressed JPEG image, and I was very surprised by the difference, as you can see in the 2 shots above.

I must admit I quite like what the camera has done in processing the image, but it does mean you lose that control in being able to do it yourself. I will cover more on processing RAW images in my next post.

It's been a long time. Step 2.

It's been nearly a year I know but some things are worth the wait. Whether this is is one of those, you decide.

So I've started the Intermediate Photography course at the Met and just though I'd keep track of things on here. This might all be a bit disjointed because it's going to be the accumulation of scribbles and assignments, so please bear with.

Week 1:

We talked a lot about portraits and lighting, with off camera flash being a main topic. DS was keen to stress that if you can afford a speedlight then great, but at the end of the day it's just a light. A cheaper model works fine; just use it on manual and turn it up or down. The one important thing to remember though is that once you've got it set, be sure to maintain your distance; move and everything changes.

Here's a link to a blog all about using off camera flash - I've had the quickest of glances and it looks good so I'll be following it and hopefully posting some results here as we go along.



Something that I've always heard but never fully appreciated the meaning of is the use of the term 'stop of light'. Increasing exposure by 1 stop means that you are doubling the quantity of light, and vice versa. This can be achieved through adjusting the aperture, shutter or ISO setting. Here's a blog post that describes it in a bit more detail:

http://cameradojo.com/2010/07/04/understanding-light-stops/

Another thing we talked about was aperture settings. Now he mentioned that F16 tends to be a good one for landscapes, and that with some lenses the quality of the picture goes down at the highest F-stop. He also said that F8 tends to be the sweet spot on a lot of lenses. I'm just jotting these things down by the way - please don't take them as a given but it may be something interesting to try out.

I asked him about shooting landscapes and where you should pick your focal point when you're aiming to have everything in focus anyway. The basic rule it seems is 1/3 in front, 2/3 behind, but he also mentioned hyperfocal distance. Basically if you have your lens focussed at the hyperfocal distance, everything from half that distance to infinity will be in focus. The hyperfocal distance is dependent on your lens and what F-stop you're shooting at. Below is a mobile web app which might be a good referenc tool, and also an article with more detail.

http://dofmaster.com/m
http://www.dofmaster.com/hyperfocal.html

Also mentioned was something I have noticed on some of my lenses - that aperture changes by itself when you zoom in. This is just a limitation of cheaper lenses, but something to be wary of when shooting in manual.

Last thing for this entry is again on the subject of light. I've just had a quick look at the websire for LEE filters and it looks very interesting. They basically make neutral density filters, which allow you stop down the amount of light for various effects. Something to investigate further...

One last thing: Full frame DSLRs are those whose sensor is the same size as 35mm film. Most DSLRs have smaller sensors, which means that when you use a lens designed or specced for a 35mm camera, only the centre of the image is captured while the edges are cropped off - the equivalent of having zoomed in.