- #1
walter1998
- 11
- 0
Hello guys, I was wondering if you could guess or even calculate the diameter of a camera lens with a picture of a ruler.
Calculating Camera Lens Diameter with a Ruler
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Discussion Overview
The discussion revolves around the feasibility of estimating the diameter of a camera lens using a photograph of a ruler. Participants explore the implications of lens size on image capture and the assumptions necessary for such calculations, touching on theoretical and practical aspects of photography.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- Some participants argue that it is not realistically possible to determine the lens diameter from a picture, as ideal cameras produce consistent images regardless of lens size.
- Others suggest that additional assumptions are necessary, such as the absence of elements that block light, to make any estimation.
- One participant proposes that understanding the probable f-number and focal length could aid in the estimation, noting that the size of the image on the sensor is a critical missing piece of information.
- There is a discussion about the implications of lens quality and aperture on image sharpness, with observations about the focus characteristics of the ruler and background elements.
- A suggestion is made to conduct a practical experiment by replicating the photograph to gather data on focal length and aperture settings, though it is noted that this would still not yield an accurate lens diameter without further information.
Areas of Agreement / Disagreement
Participants generally disagree on the feasibility of estimating the lens diameter from the photograph, with multiple competing views on the necessary assumptions and information required for such an estimation.
Contextual Notes
Limitations include the dependence on assumptions about lens characteristics, the quality of the lens, and the conditions under which the photograph was taken. The discussion highlights the uncertainty surrounding the relationship between lens size and image characteristics.
Who May Find This Useful
Individuals interested in photography, optical physics, and those exploring practical applications of theoretical concepts in imaging may find this discussion relevant.
- #2
mfb
Mentor
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Not in any realistic way. An ideal camera will make the same picture independent of the size of the lens, and real cameras are quite close to that (and for the tiny deviations, you have no idea which part of the camera lead to them).
- #3
walter1998
- 11
- 0
This question is asked in a famous competition in my country: "Approximately calculate the diameter of the lens which this picture is taken with.(for measurements consider lens as a flat object)mfb said:
- #4
mfb
Mentor
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Ah well, you also have some background here that can be useful. And I think you still need some additional assumptions (like no additional elements that block light).
- #5
sophiecentaur
Science Advisor
Homework Helper
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I think this is to do with probable f number and focal length. There are some clues to help you but the main bit of information that is totally missing would be the size of that image on the film / sensor assume it is an APS sensor?? perhaps.. Firstly, the ruler looks pretty straight, unless the lens is very expensive, we are not dealing with a very short focal length. The window frame is probably not far from the ruler and is badly out of focus so the aperture must be fairly wide (poor depth of focus).
The left side of the ruler is a bit soft so that could suggest either a poor lens or a wide aperture. You can make assumptions about the probable width of the window frame and then guess how far it is behind the ruler. That would give a clue about how far the camera is away from the ruler (draw some sketches).
I could suggest you take a camera of your own and try to reconstruct a similar picture (with buildings in the distant background - or is it a fence, only a few metres away?) and note the focal length and f setting. That will give you the width of the internal aperture but it cannot tell you the diameter of the lens without a lot more information.
There is no way you can get an accurate estimate but, like estimating the number of sweets in a jar, you can avoid giving really wrong estimate.
The left side of the ruler is a bit soft so that could suggest either a poor lens or a wide aperture. You can make assumptions about the probable width of the window frame and then guess how far it is behind the ruler. That would give a clue about how far the camera is away from the ruler (draw some sketches).
I could suggest you take a camera of your own and try to reconstruct a similar picture (with buildings in the distant background - or is it a fence, only a few metres away?) and note the focal length and f setting. That will give you the width of the internal aperture but it cannot tell you the diameter of the lens without a lot more information.
There is no way you can get an accurate estimate but, like estimating the number of sweets in a jar, you can avoid giving really wrong estimate.
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