Monthly Archives: March 2016

Exercise: Camera’s Dynamic Range (DPP)

This exercise was about finding the dynamic range of my camera (Nikon D5500)

A cameras dynamic range is the difference between the lightest light and darkest dark which can be seen in a photo. Once the subject exceeds the camera’s dynamic range, the highlights wash out to white, or the darks become black blobs (noise).

I had to find a high dynamic range scene with the following conditions:

  • bright sunlight
  • at least one brightly reflecting surface
  • an area of deep shadow with a dark surface

I must admit i’ve been fairly stumped by this exercise. I noticed that many student blogs were missing this exercise. Having researched online extensively and having studied other student blogs and discussed in forums I think i’m somewhat clearer. Some articles adjust aperture while others adjust shutter speed. I’ve decided to crack on with it and not waste any more time deliberating over it.

In a nutshell – using a fixed ISO and aperture I am going to measure the difference in shutter speeds of different areas of brightness in one image. Spot metering will help me identify the correct shutter speed. The range between these results will be my camera’s dynamic range.

Firstly I had to set the exposure and make sure the it was just at the point where there were no longer any highlight clipping warnings on the reflecting surface (white wall).  The exposure settings where the highlight clipping had just disappeared  was 1/200, f.22 and ISO 400.

Original

Next I had to measure and make note of the brightness of the white wall and two or three of the darkest shadows.  I used the spot metering setting as this enables me to measure specific areas.  I measured the white wall at 1/640, f.22, ISO 400.  I then measured 2 dark shadow areas (the bricked pavement area and the dark shadow by the palm and wall) as 1/60, f.22, ISO 400 and 1/30, f.22, ISO 400 retrospectively.

With numbers

Part 2 required me to open the image to 100% in my software and check that the white area’s pixel values showed just under 255 on all three channels. They measure at 249 on all 3.

I was the required to zoom into the shaded area, brightening it with my software and comparing the areas of real detail against noise.

Screen Shot 2016-03-20 at 12.06.49

As you can see from the above image it is now extremely difficult to tell the difference between detail and noise. The darkest areas are extremely hard to determine.

SO now i’ve got my shutter seed variations I need to calculate the dynamic range. The OCA handbook states that most SLR’s have a range of roughly 9-10 Evs.

The Nikon i’m using has a total range of 1/4000 to 30secs, but i’m just going to look at the values i’m working with:

1/640

1/500

1/400

1/320

1/250

1/200

1/160

1/125

1/100

1/80

1/60

1/50

1/40

1/30

I seem to have produced a dynamic range of 13 Ev’s – this seems a little excessive considering the average is 9-10. However, after researching the average dynamic range of my model I came across this website http://www.dxomark.com/Reviews/Nikon-D5500-sensor-review-Low-noise-and-class-leading-dynamic-range/Measurements-Nikon-D5500-Excellent-dynamic-range that mentions the Nikon D5500 having a range of 14 EV’s.

Therefore i’m happy with my results, and have learnt how important this feature is when assessing shots. It’s essential while maintaining a technically satisfactory image, but is also a great creative tool for producing silhouettes, and generally making photos more art like and aesthetic.

 

 

 

 

 

Exercise: Colour Cast and White Balance (DPP)

For this exercise we are to alter the white balance on several different scenes.

I felt like this exercise was very close to one from a previous module:

https://saffroncuccio.wordpress.com/2014/09/26/exercise-tungsten-and-fluorescent-lighting-taop/

While the exercise above dealt with tungsten and fluorescent lighting only – I feel like I am already very aware of the impact of altering white balance.

As this exercise has called for sunlight AND open shade on a sunny day I’ve decided to move on as It’s extremely dark and miserable outside and I don’t want this exercise to slow me down more.

I incorporate white balance settings in all my photography and am very aware of it’s impact.

Exercise: Highlight Clipping (DPP)

For this exercise I have to find a scene with a wide range of brightness and shoot in manual mode. I must find the setting where the highlight clipping warning starts to appear and make a note of the setting. I then have to increase the exposure by 1 F stop using either aperture of shutter speed.

Then I must take 3 more shots decreasing the exposure each time by 1 F stop.

I have to process the images  without making any adjustments and then observe a magnified area of the highlights; making notes on:

  • Completely lost areas of visual information
  • A visible break in the form of an edge between nearly-white and total white
  • A colour cast along a fringe bordering the clipping white highlight
  • The colour saturation

F5.6

F. 5.6 ISO 200 0.3/sec

At these settings the highlight clipping warning is now flashing on the white part of the wall between the guitar neck and black wall.

F4.5

F.4.5 ISO 200 0.3/sec

Now at a higher exposure the highlight warning practically covers the whole of the white wall and a few characters on the black chalk wall. The colour saturation is off, the guitar demonstrates this well. The white wall has a large area of lost visual information.

F7.1

F.7.1 ISO 200 0.3/sec

Image three shows no highlight clipping warnings. There is no loss of visual information in the highlight areas and no breaks between areas of nearly white and total white. The colours (mainly the guitar and calendar) become more saturated with each decrease in exposure.

F9

F.9 ISO 200 0.3/sec

Image four is now starting to appear too dark and under exposed. The colours of the text on the chalk wall are becoming less visible.

F11

F.11 ISO 200 0.3/sec

Image five is now far too dark compared to the original image (F.5.6) There’s not one part that is correctly exposed. I don’t think that it is so dark that it would be rendered useless, but compared to the first image it is severely under exposed.

Conclusion:

I wonder if perhaps I would have got slightly different/stronger results had I used a scene with more variety. The shot is dominated by white, which may have hindered my results slightly. Had I used a smaller area of white, possibly repositioned in the shot (i.e not covering a large space) and not contrasted with black, but some other colours this exercise may have worked out differently.

However, it’s all about trial and error and I am aware of the importance of highlight clipping and it’s effects after finishing this exercise.