How do you calculate the distance change needed to match framing at a different focal length?
Asked 9/20/2012
0 views
2 answers
0
If a subject fills the frame at 10mm from a given distance, how far back would you need to move when using a 17mm lens to get the same subject framing? Is there a simple way to calculate this, and does changing distance make the image look the same overall?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
8
Object size in the frame has a simple linear relationship to focal length, so if you're filling the frame at 1 meter with the 10mm lens, you'd have to step back to 1.7 meters to get the object in the frame with a 17mm lens.
It's worth pointing out that stepping back and using a longer focal length is not a direct substitute - you will end up with a different looking image. Specifically you will have less background in shot (background objects will all appear larger) and you'll have a flatter, slightly more natural looking perspective.
This technique is often used by portrait photographers who step a long way back and tend to shoot at 85mm or more. The flatter perspective is more flattering, for example the "smaller background" effect of a 10mm would make the face look smaller in comparison with the nose, thereby making the nose look bigger than it would look to the human eye.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
Generated from our catalog & community — verify before relying on it.
For the same subject size in the frame, distance changes in direct proportion to focal length. So you can use:
new distance = old distance × (new focal length / old focal length)
Example: if the subject fills the frame at 1 meter with a 10mm lens, then with a 17mm lens you would move back to:
1 × (17 / 10) = 1.7 meters
So yes, there’s a simple linear relationship for matching framing.
However, matching framing this way does not produce an identical image. When you step back and use a longer focal length, perspective changes because camera position changes. The subject may be framed similarly, but the background will appear larger and you’ll usually include less of it. The overall look becomes flatter and often more natural-looking, which is one reason portrait photographers commonly use longer focal lengths from farther away.
Recommended products
UniqueBot
AI13y ago
Your Answer
Related Questions
How do I calculate how far to move to keep the same framing with a different focal length?
How do focal length and field of view relate for an equisolid fisheye lens?
How can I estimate the focal length I’ll need for a given subject size and distance?
Does background blur change with focal length when subject framing stays the same?
Does focal length change depth of field if subject size stays the same?