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Help With Focal Lengths On Camera?

Digital Cameras Discussion

Help With Focal Lengths On Camera?

Postby Zander » Sat Sep 16, 2017 2:31 pm

I'm taking a photography course and this is my assignment:

Using 5 different focal lengths and keeping all other conditions the same, show the photograph at the different focal lengths (need to see a change in the size of the image).
Be sure to include the focal lengths used along with the date and time the photos were taken.

but the only numbers on my lens are 38, 50, and 76

so how am i supposed to know what focal length i'm using? and 5 different ones?
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Help With Focal Lengths On Camera?

Postby justis » Sun Sep 17, 2017 3:06 pm

Low grade lenses can exchange optical high quality alongside the focal length. Even the suited zooms can demonstrate some degree of exchange below laboratory situations (yet those are interior the measurable yet no longer sizeable class). in case you opt for the very suited optical high quality, then best lenses are nevertheless the suited. however the very suited zoom lenses are solid sufficient for many purposes, and the ease of the zoom vs. optical high quality is justifiable. yet junk zoom lenses, distinctly those poor 35x and better bridge lenses are sufficient have sizeable optical subject concerns at particular focal lengths. additionally there's a distinction between expert and customer grade zoom lenses. expert grade lenses guard the optimal aperture alongside the focal length, jointly as customer grade lenses lose gentle amassing potential (decrease optimal aperture), as you zoom to the longer focal length. This regardless of the undeniable fact that, has greater to do with low-gentle useability than lens high quality.
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Help With Focal Lengths On Camera?

Postby Princeton » Wed Sep 20, 2017 12:17 am

Shoot the five different photos, upload them into your computer, open up their properrties (Right-click>Properties), and it will TELL you what the focal length was at time of shooting. This only works with digital lenses, mind, so older lenses may not show this... All EOS cameras tag the focal length, and all lenses made after 2002 will probably have this feature. (Pentax lenses also tag these if they have contact points on the lens base).
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Help With Focal Lengths On Camera?

Postby Gillecriosd » Thu Sep 21, 2017 11:22 am

Maybe your camera has a fixed focal length lens installed. For five different FL you would need either a zoom lens or four other lens to attach.
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Help With Focal Lengths On Camera?

Postby Leighton » Thu Sep 21, 2017 1:51 pm

Firstly what camera + lens combo are you using.
Is it film or digital? If it's digital, then you will be able to read the exact focal length your lens is set at from the EXIF data.

The focal lengths are usually marked around the lens barrel (or in some older film lenses, through a little window on the barrel) - there will be an index mark to line up where the zoom ring is in respect of focal length.

All zoom lenses have intermediate focal lengths between the major ones marked.

Have a look at this pic; http://i1088.photobucket.com/albums/i339...

it's a Nikon 18-55mm lens (Canon will be similar).
The lens zooms between 18mm and 55mm.
In the pic, the white dot is lined up with the 35, meaning the lens is set at 35mm.
You do not have to be exactly at a number - the lens can be used anywhere on the scale.
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Help With Focal Lengths On Camera?

Postby Marden » Wed Sep 27, 2017 1:13 am

Hi Hay,

It would be helpful to know what brand/model camera and lens(es) you have and whether you are using a digital or film camera.
If your camera doesn't have interchangeable (removable) lenses you will have to work within the limits of the camera.

I am guessing that you have a camera with a zoom lens that goes from 38~76mm (wide angle to telephoto) and, if it is a digital camera, the numbers are probably "35mm equivalent" values.
The total "Zoom" ratio of the lens is a relatively low 2:1 (2X) which is calculated by dividing the higher number by the lower number.
This will make your assignment a bit more difficult because a lens with a 3:1 or 4:1 ratio would give more noticeable differences but if you set the camera up on a tripod or stable surface and shoot a series of pictures you will be able to accomplish your goal.

My approach would be to set the camera up and compose a shot at the widest angle (38) setting, preferably of a scenic subject or street scene, with some objects near the camera and others further away in the distance.
Once you know how the wide angle shot will appear carefully adjust the setting to 76 without moving the camera and shoot a picture; then set the lens about halfway between 76~50, shoot another picture; set to 50, shoot; halfway between 50~38, shoot and finally, set to 38, shoot and process your images so that each one is entirely visible and they are all displayed in the same size.
This will give you a series of photos with 5 different angles of view that will show slightly more of the scene as the wider settings are used.
What you should also take note of is whether any details appear more clearly and how things in the background and edges appear from one photo to the next.

If you are using a digital camera be sure to set the date and time on the camera BEFORE you take any pictures.
When you process digital images be sure to look at the EXIF data associated with each image, it should have the date and time, shutter speed, aperture and focal length available.

Here is a link to a photo with the EXIF data revealed on Flickr. http://www.flickr.com/photos/robs-photo-...

If you are using a film camera you will most likely need to take a small notepad or index card to record the date, time, shutter speed setting, aperture setting and lens focal length before each exposure.
Note that you intermediate settings should be recorded as "estimated" (about 44 & 63) if you use the suggested settings above.

Hope that helps.
Feel free to contact me via the email link in my profile if you need additional help.
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