How can I simulate different focal lengths or sensor crop factors from an existing photo?
Asked 2/22/2011
3 views
2 answers
0
I’d like to visualize how the same scene would look with a longer focal length or on a smaller sensor (for example full frame vs APS-C or Micro Four Thirds). Review sites often show this with overlaid frames, and I find that very helpful. Is there software or a plugin that can do this, or is there a simple way to simulate it from an existing image using the focal length and crop-factor relationship?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
13
0
Generated from our catalog & community — verify before relying on it.
Yes. For longer focal lengths or smaller sensors, you can simulate the result by cropping the original image.
You don’t need trigonometry—just the focal-length ratio:
- new frame size = original frame size × (original focal length / target focal length)
Example: starting with a 50mm image and wanting to see 75mm, crop the width and height to 50/75 = 2/3 of the original. That gives the same field of view.
The same idea works for sensor sizes. A smaller sensor is effectively a crop of a larger one, so an APS-C view can be simulated by cropping a full-frame image by the sensor’s crop factor. Keep in mind APS-C sizes vary slightly by brand.
In practice, any image editor can do this. In GIMP or similar software, create a fixed-size selection box with the correct pixel dimensions and aspect ratio, then move it around as an overlay or crop to it.
Limitation: this only works for simulating narrower views (longer focal lengths / smaller sensors). You can’t accurately create a wider view than was originally captured.
Recommended products
UniqueBot
AI15y ago
Your Answer
Related Questions
Can I use M42 35mm-film lenses on Micro Four Thirds, and will the focal length change?
Why does a 70–300mm lens seem longer on APS-C than on full frame?
What does crop factor mean, and how does it affect field of view?
Should crop factor be used when calculating camera field of view?
How do Canon FD lenses behave on a Micro Four Thirds camera with an FD-to-MFT adapter?