Sunday, January 10, 2010

Project 49

As preparation for this exercise I purchased a Cokin grad filter set with 3 filters in x1, x2, and x4 stop strengths. I already had a 77mm circular 2 stop grad filter, that I have used on vacation to darken the very bright tropical skies.  The square filters from Cokin have the advantage that the boundary can be adjusted up and down and that they can be combined with other filters.  The problem I have is that they vignette on a 24mm lens, my most commonly used wide angle, so in the following images I have cropped slightly.

The photos are taken overlooking one of the main bridges in Munich from the top of a small rise, enabling a broad view of the city and including good foreground detail and a substantial amount of sky.

The first image was taken by simply pointing the camera and hitting the trigger

5D2, 24-105mm, 24mm, f/4, 1/1000, ISO 400

This is clearly underexposed as a result of the large portions of the images that are more or less white.  Increasing the exposure by one and a half stops produced a better balanced image with white snow, but with the sky nearly completely blown out

5D2, 24-105mm, 24mm, f/4, 1/350, ISO 400

Now fitting the grad filters at increasing strengths I produced the following 3 images.  In each case I have maintained the exposure manually at the same value as the previous image

The middle image with the 2 stop filter preserves the cloud structure best of the images.

The indoor exercise was interesting, I had not considered using a grad filter on its side to darken part of a room.  I used my home office to produce the suggested image.  I fixed my camera at one end of the room, with the window to the left and took the following image using the cameras metering:

5D2, 24-105mm, 24mm, f/8, 20s, ISO 100

I immediately realized that because my room was fairly small I was seeing the opposite affect to the one suggested in the text.  The door on the right side of the frame was strongly reflecting the light and was being washed out in the image.  I used a hand held meter to check the incident light level across the room.  Keeping the aperture and ISO at f/8 and 100 respectively, I measure the following

Left hand wall: 30s
rear book case: 25s
right book case 10s
right hand door: 4s

So the small room was better illuminated opposite the window.  To rectify this I tried mounting the grad filter with the dark part to the right of the image.  I maintained the exposure as before and captured the following two images with the 1 and 2 stop grad filters

In each case I tried to align the filter edge along the right corner of the room.  The 1 stop filter balances the image well, bringing the brightness of the right hand book case down to that of the rear one and preventing the door from being washed out. At 2 stops the door becomes too grey and the right hand book case is now darker than it needs to be.

No comments:

Post a Comment