Monthly Archives: March 2013

Photographing a model backdrop

I decided my model train layout (Märklin Z) needed proper background image (a backdrop). If you google for it, you find many nice backdrops for sale. Those are probably fantastic, but I did not find one that works for me.

I will start with the result.

Backdrop

This is a panorama that is 180×15 cm, and most standard backdrops I found were not so extreme panoramas as I wanted. Also, when making it myself I could get the landscape I wanted.

Photographing
This is what you need:

  1. A location with unobstructed view over the horizon
  2. Good weather conditions, preferably the sun in your back
  3. A tripod

And of course, you need a camera. I made use of the following features of my Nikon P7000 when photographing my panorama.

  1. RAW mode (to ensure white balance etc are identical for all pictures)
  2. Delayed shutter or remote shutter (to keep camera absolutely still)
  3. Manual mode (you want the same shutter speed and aperture for each picture
  4. Grid 3×3 (to help with proper overlap
  5. Horizontal indicator (to help getting the horizon straight
  6. 200 mm equivalent zoom (to be able to take several pictures at a limited horizon stretch)

I only rotated the camera using the tripod between each picture, keeping the horizon exactly in the middle of the pictures, and I let the pictures overlap 1/3.

Essentially, the math goes like this. I wanted at least about 150-200 dpi for my final print of 180 cm. This requires a picture that is about 15000 pixels wide. Ideally I would use a camera with 15000×10000 pixel sensor (that is 150MPixels) and just crop the picture. I have no such camera, but my Nikon P7000 is about 3600 pixels wide. With an overlap of 1/3, it means each picture contributes with only 2400 pixels, so I need a series of about 6 pictures to get a 15000 pixels wide result. Now this is where telezoom comes into play. At 200mm, each picture is about 10 degrees. The more telezoom you can get, the shorter horizon you can work with.

Dont overexpose! You want the sky blue – not white. If you have UV filters and stuff – great. But I suggest you underexpose a bit.

Panorama stiching
I used Ubuntu and tools that come with it to create my panorama.

First I imported all my series into Shotwell. That means, I let Shotwell do the RAW developing, which turned out ok (all pictures had the same white balance, etc) – perhaps I was just lucky. I picked my best series, and exported all pictures from that series at highest quality.

Second, I used Hugin Panorama Creator to create the actual panorama. I choose Lens Type = Panoramic (Cylindrical). This is a lie (and at 200mm it is a small lie), but it created the completely straight horizon I wanted.

Finally, I did some cropping and color adjustments in Gimp.

Printing
How to print something that is 180×15 cm? My first idea was to print several standard 15×10 cm photos and just display them next to each other. Problem is, you never know if the crop your pictures a little bit, and in this case it would destroy the result completely.

I ended up (in Gimp), cutting my 15000 pixel panorama into 3 pieces (each 60x15cm), and pasting the 3 pieces to a 5600×4000 image. I left white margins around each piece.

I then sent my single big picture to print on standard photo paper in 70x50cm. I cut out the 3 pieces with a razor and mounted them next to each other.

Conclusions
I did not have so high expectations. My plan was to learn from my first attempt and do everything over again a few times. But my first result was really above expectations – and very much good enough for my purpose.

You do not need higher DPI than I had (15000 pixels for 180 cm). You can probably do with less.

I am very happy with my sky (~RGB=135,166,186) and the sea colors (~RGB=32,63,97).

Printing on normal photo paper was good – the result is nice. The edges between them are not perfect though.