Focal Length Doubts

[Ravani]

Hi! I'm just learning about focal length and there are some things that I still don't understand. But what mostly intrigues me is this:
I was analyzing some photos and some of them shows 24mm and 32mm, but also there are some 3.24 and 2.52.
What means those 3.24 and 2.52?

[Manfred M]

Welcome to CiC. If you wouldn't mind clicking the "My Profile" tab at the top of the page and completing the information about yourself, that would be very useful; at least adding your first name and where you are from? We tend to work on a first name basis here at CiC.

Digital cameras are made with sensors of various sizes and consequently, the lenses used on them have varying focal lengths. The first set of numbers you give could indicate focal lengths of lenses used on cameras that use a large sensor size; full-frame, APS-C or micro four-thirds, and the second set could be used on cameras that use a small sensor size like 1/1.7" or 1/2.5".



As you can see from the diagram, standard sensor sizes can vary greatly. A lens of a specific focal length will always cast the same size of image, so a 32mm focal length will be a wide angle lens on a full frame sensor camera, a "normal" lens for an APS-C sized sensor and a telephoto lens on one of the smaller sensors.


My answer is just a guess as to what you are looking for...

You'll have to explain what you are after a bit better for us to provide better information you are looking for.

[Ravani]

Thanks for the answer GrumpyDiver!

I'm getting a great interest and excitement about photography, but is kinda a hobby. I was just learning about Focal Length then I took a look on some photos of friends of mine and checked the focal length section on those.

Most of them had the first set of numbers and I understood about those. But the second set got me, I didn't understand what means the number before the dot: 3.X, 2.X

My friend told me those photos was taken with a digital compact camera.

[Manfred M]

Celso - I suspect that you are overthinking this. Focal length (depending on the camera being used) is generally selected for technical, practical and compositional reasons.

A sports photographer will likely choose a long focal length, because he or she cannot get close to where the action is taking place. An architectural photographer might choose a wide-angle lens because he or she is trying to capture the view of an entire room inside of a building. A portrait photographer might choose a long focal length lens to get a shot of a person so that the image looks pleasing but will shoot with a wide angle or normal lens when taking group shots.

Lens selection (and this is more than just focal length) will largely depend on the type of photography, lighting conditions. effects and of course cost of the lens.

[dem]

Can the latter be "focus distance"? That is the distance between the camera and the subject measured in meters.

[xpatUSA]

We need to know how you analyzed the photos and where in your analysis program it said "3.24 and 2.52". Until, then we can only guess at what "3.24 and 2.52" means. Can you post a photo somewhere that contains the mystery numbers?

I can then download it and examine it with ExifTool and tell you what they mean. Please don't "save for the web" - it deletes EXIF data, I think.

[xpatUSA]

Can the latter be "focus distance"? That is the distance between the camera and the subject measured in meters.

I think you're right. I was just looking at a Nikon 7200 JPEG with ExifToolGUI and, under "Maker Tags", 'FocusDistance' is right above 'FocalLength' and has a number in meters to two decimal places. Hopefully our friend from Brasil is still with us . . . .