Exercise 1 : Measuring Exposure (Project – the Intensity of Light)

Part 4 : Light

Exercise 1 : Measuring Exposure (Project – the Intensity of Light)

My Canon 500D DSLR camera has four metering patterns;-

  • Evaluative – (aka smart predictive and matrix). This is an all-round metering mode where the exposure is set automatically to suit the scene.
  • Partial metering – Effective when the background is much brighter than the subject due to backlighting etc. The metering is weighted more in the centre.
  • Spot metering – for metering a specific part of the subject or scene.
  • Centre weighted average – the metering is weighted at the centre and then averaged for the entire scene.

When I first got a DSLR (just over a year ago now) I kept confusing, for example,  spot metering with spot focussing and it’s taken me some time to appreciate that I can have different combinations and also that I can lock the exposure with the exposure button star button and change the focussing pattern by pressing another button. It’s fine when I’m photographing a scene and there’s time to set everything up, including the tripod, but still problematic for me at times when I want to take a photograph quickly because of what’s happening around me. So far, though, I’ve managed to avoid the temptation to just go into auto or program mode.

This first exercise has been a mix of experimentation and miscalculation – not helped by the fact that I’ve also recently acquired two new lenses and wanted to practise with them. The  135mm Canon lens doesn’t have image stabilisation and I need to ensure I have the right shutter speed to avoid camera shake without a tripod. The Samyang 24mm lens is optically excellent but all the technical knowhow has gone into this and it is manual only.  This means that  I’ve had to get used to using the histogram to check if I’m getting the correct exposure. For some photographs I also used my Fuji Finepix X100 and a Canon EF24-105mm zoom lens .

Unless I write otherwise, I have only reduced any apparent noise and/or  sharpened the exercise images. I also stayed with auto white balance to maintain consistency.

4 to 6 photographs deliberately lighter or darker than average

1)  

It was early morning on a dark day. Because of all the greens I thought that a garden scene would be a low contrast image, so decided to increase exposure half a stop to see if it would suggest a brighter day.


135mm @ 16.5m f11  8.0   evaluative metering

The scene is certainly brighter but it looks wishy-washy as well. Because my eyes were full of green and red I hadn’t remembered we have some brighter, orangey roses and  other flowers as well. This meant that there was clipping on the highlights and a loss of sharpness there as you can see.  In Photoshop I did experiment with decreasing the exposure there which improved it but it didn’t alter the fact that the orange rose wasn’t sharp enough.

2) 

I decided to now reduce exposure half a stop

f11 2.5

There was still slight clipping on the rose. I could have used spot meter but it was actually a very small part of the scene and I thought that , if I had done so, everything else would be much too dark.

3)

Taken from an upstairs window with Fuji at f11 1/30th  Pattern/evaluative

This was taken at minus 1 exposure because I’d realised from previous colour exercises that this can deepen the colour. Here I was endeavouring to bring out the colour after the rain.

4)

Fuji f5.6 1/30 (minus 1) pattern/evaluative

It was dim inside my room. The histogram shows some loss of detail in the shadows on the window frame but I had reduced the exposure through focus on the pale card as I wanted to bring out its design.

Differing exposures on the same scene

5)

Close-up of roses. All 135mm @1.7m. f11 evaluative.

a)  1 second



b) 0.5

 

c) 0.4

 

d) 1/4


e) 1/6



d)  is the one that the camera measured as at the correct exposure.  I prefer  e)  and, again, this confirms what I discovered in the colour exercises that slight under-exposure brings out a deeper colour.

6

All taken using Canon EF24-105mm zoom lens from a distance of 6.5 metres with evaluative metering. The lens is my husband’s –  the first day I’ve used it and I like it. Unfortunately he says he won’t let me keep it because it’s his everyday lens. We did a quick swap because he wanted to use my 14mm Samyang lens.

a)


40mm f8  1/30

The camera showed this was the correct exposure, but I could see highlight clipping on the histogram which was the bright sky between the tree branches, the road, church path and edges of gravestones.

b)


35mm f8 1/25

I moved slightly, also widening the lens a little in attempt to reduce the highlight clipping, which worked to some extent.

c)

40mm f8 1/50th

I decided to expose for the sky this time and then recompose. The trees now look dark and heavy though and there was still a little highlight clipping.

d)


This is a re-working of 6c.In Adobe Bridge I used the recovery slider to deal with the highlight clipping; fill light to deal with the shadows and raised the exposure level very slightly.  I then created an inverted ‘S’ in levels and increased centre luminosity in Nik Color Efex Pro.

7

Inside St Nicholas Church, Pyrford, Surrey, which is C11th and small and dim inside.. I used a Samyang 14mm lens at f8. I’m sure now that I could have used 5.6.  This is a new lens and I’m only just getting used to its properties and the fact that it hasn’t got a full electronic link with my Canon camera.

I got quite obsessed with this shot. A while ago I visited Canterbury Cathedral and took a shot in the cloisters where it was dim inside but a lot of light coming in from the quadrangle.  It had been a quick shot of two choristers in red gowns so there wasn’t enough time to really think about the exposure.  Afterwards I decided that the perfect shot would have been where I exposed for the light but had a fill in flash to cope with the dark.  Of course, I would have needed a tripod as well.  A difficult manoeuvre still though for a chance shot.

On this occasion, I had the tripod and plenty of time but I still couldn’t get it right!

a)


4 seconds on evaluative. You can see how over-exposed it is and all the detail has been lost from the window (middle of the day and light coming strongly through it.) I can see a lot of the detail on the runners  and pews though.

b)


0.6 on evaluative and there is now a little more detail on the window.

c)

0.4 and I decided to use spot metering on the window this time.  This histogram still showed highlight clipping.

d)


¼ on spot. There was less highlight clipping but detail is very lost lost in the shadows.

I decided to use my Photomatix software and firstly attempted HDR using the first image, middle and last but it looked quite odd. Then I did an exposure fusion.  This would have worked except that I’d forgotten that I’d readjusted my camera after the first shot so there was too much ghosting.  I had to put the first image to one side and then do an exposure fusion using a different image.h

This is the result:-

e)

I think this is too light and it doesn’t give the same feeling that I get when I’m actually in the little church.

After this I worked on 7d to see what would happen when I used the burn tool on the window:-

f)

8

24-105mm lens @ 24m.  f11  1/125.  Here I diverted from the exercise brief to experiment and used the same photograph,  altering the exposure in Adobe CR. I did this on the assumption that, if the exposure was correct to begin with there wouldn’t be highlight clipping.

a


Original exposure. Exposed for the sky and the church spire.

b


-1 exposure.

c


+1 exposure. It looks ‘washed out’ and the spire is pale.

9

24-105mm lens @ 28m

a


this was exposed for the sky and some detail has been lost in the shadows.

b

I used the same photograph and didn’t alter the exposure levels.  Instead I used fill light in Adobe CRto see if I could gain more detail in the shadows and levels on auto, plus some tonal contrast in Colour Efex Pro.

Summary

I learned quite  a lot from this exercise:-

  • Some underexposure works well on flowers and foliage as it brings out the colour.
  • Over-exposure (and consequent clipping) affects the sharpness of an image so it’s best to use spot exposure metering on brighter parts and then deal with the shadow detail in processing.
  • If the highlights are too clipped then playing around with exposure in adobe CR won’t bring back detail that wasn’t there in the first place..
  • Large extremes of contrast are difficult. You either have to decide which is more important and expose accordingly or use bracketing.  Exposure fusion can work quite well if you’ve used a tripod and don’t alter the position of the camera.
  • With regard to  the gloomy church and bright window – I could have exposed for the window and then used soft fill-in flash maybe at each side of the pews if I had the apparatus. That would be more complicated.
  • I made life complicated for myself by using several different, new, lenses.

6th September 2011

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