Martha Is Dead

You'll need to acquire the infrared film and lens accessory for your camera that can be found in chapter 5 (The Rolls, located in the darkroom) and the tripod that can be found in chapter 6 (The Woods, located in the basement near the workbench). When there is an opportunity to capture an IR picture, a small icon that looks like your camera will appear on screen, with the initials IR on the bottom of it (on the main gameplay screen, nothing will appear on the map for these locations). Note that you must take and develop each photograph in order before the next one becomes available.

Chapter 6 – The Woods
IR Photo #1: the back wall in the cellar area with the wine casks
IR Photo #2: behind the small church in the courtyard, on the side closest to the gate leading to the crossroads
IR Photo #3: go out of the gate and to the crossroads, on the right at the start of the path going uphill to the graveyard
IR Photo #4: near the small bridge on the northernmost of the two paths that end at the lake - not available until later in the chapter, when your objective tells you to go to the woods,

Chapter 8 – The Burial
IR Photo #5: in the woods at the end of the southernmost path that ends at the main stream, by a cross
IR Photo #6: go out of the gate and left at the crossroads, above the cross in the field of poppies

Once you develop and print photo #6, you can then start on the Judgement achievement:

You first need to obtain the IR film and lens (in father's study or in the darkroom) and tripod (basement near the outer door).

Then, you have to take the IR photos. In each correct location, you'll find the camera-with-IR symbol. After taking a photo, return to the darkroom and develop it to reveal a hint for the next location.

The locations:

1. In the basement, in the dead end between the large wine casks.
2. Behind the little chapel in the corner of the yard, toward the forest
3. At the crossroads, down through the gate and bridge, in the bushes
4. In the forest, the little plank bridge over the small stream, close to the lake
5. In the forest. Follow the southernmost path until you come to the stream, with a grave atop a little ridge. (If you go the wrong way in the forest, you come to the stream with the target too far away. Go back and follow the other path.)
6. Go down to the crossroads again and take the eastern path until you find a flower field with red flowers and a cross.