Lens focal lengths - selecting the correct ones

Stephen McLees

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Hi Everyone.

I recently purchased my first DSLR and with it a an 18 - 140mm lens.

I really struggle to get my head round focal lengths and what the best ones are for specific situations.

Anyone have any tips on what that Lens is best for, and how best to decide what length to use for what photos?
 

Space Face

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What you looking to take pictures of?
 
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Stephen McLees

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Anything and everything really. But I really enjoy trying to get close up/magnified shots
 

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Which DSLR - APS-C has a crop factor relative to full frame so the way you approach focal length is different.
 
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Stephen McLees

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Yes macro.

Nikon D5600
 

480sparky

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There is no such thing as a list of "You're photographing _______, so use ___mm".
 

Grandpa Ron

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The easiest way to look at it is focal length is as an equivalent to magnification. There are lots of other things such as depth of field and shutter speed that are at play. However, if you are just starting out, you will use the lens to zoom in or out, to crop the photo you want to take.

After a while you will notice that when you zoom in or out the aperture may change. This is because the amount of light hitting the sensor changes and the camera automatically re-sets the aperture and or the shutter speed. This then effects the depth of field or the ability to stop motion etc.

After a while most folks move off of auto because the want to control the shutter speed, aperture and/or the ISO rather than let the camera do it. For example when I do a close up of a flower, I move to aperture priority and manually set the aperture to a lower f stop to limit the depth of field. Then anything behind the flower is out of focus. If I wish to catch birds in flight, I will move to shutter priority and set a fast shutter speed to stop the wing action. The camera adjust the other variable for a proper exposure. At times I go completely on manual because I want try something really unique.

As always, the way you learn these things is to listen what other do, then practice practice practice.

Good Luck
 
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mjcmt

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Hi Everyone.

I recently purchased my first DSLR and with it a an 18 - 140mm lens.

I really struggle to get my head round focal lengths and what the best ones are for specific situations.

Anyone have any tips on what that Lens is best for, and how best to decide what length to use for what photos?
The best way to find out is to shoot with your camera/zoom lens kit this spring and summer. Then look at the data of your favorite shots to see what focal lengths you use the most. Even basic photo editing programs will tell you this. Then you can find what you like the most.
 

smoke665

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Beginners invariably get G.A.S. (Gear Acquirement Syndrome) soon after their first camera purchase. The problem with that, is everything is so new, you have no idea where exactly your interests lie. You're lucky in that you have a wide range of focal lengths in the lens you have. Rather than rushing out to buy something now, why not use what you have for a bit, try shooting at various focal lengths while reading up on different types of photography. When you do you'll likely know what you want or at least be better able to phrase your questions for specific answers.
 
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Stephen McLees

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Just on this, while I'm looking at reviews for lens. Does the lens I have (18 -140mm) when set at 50mm do the same job as a Prime 50mm lens?
 
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Stephen McLees

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Beginners invariably get G.A.S. (Gear Acquirement Syndrome) soon after their first camera purchase. The problem with that, is everything is so new, you have no idea where exactly your interests lie. You're lucky in that you have a wide range of focal lengths in the lens you have. Rather than rushing out to buy something now, why not use what you have for a bit, try shooting at various focal lengths while reading up on different types of photography. When you do you'll likely know what you want or at least be better able to phrase your questions for specific answers.

Yeah, I think you have hit the nail on head there
 

smoke665

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Just on this, while I'm looking at reviews for lens. Does the lens I have (18 -140mm) when set at 50mm do the same job as a Prime 50mm lens?

Yes and no. Will your zoom set to 50mm give the same FOV (field of view) as my 50mm f1.8 prime....yes. Will it give the same image quality, probably not, but not so much difference that the average viewer would notice, nor will your zoom have the same ability to open up to f1.8. However it will allow you to practice and learn how focal length affects perspective.
 

nokk

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i generally view focal lengths as a tool to achieve a certain perspective. imagine shooting shooting a scene at 50mm with a tree on either side of the frame, a house in the center and the top of the roof line will run along the top of the mountains in the background.

or you can get closer and shoot the same scene at 20mm with the two trees in the same spot, house in the center and the roof will go above the mountains in the background.

or you can stand further away and shoot the same scene at 200mm with the two trees in the same spot, house in the center and the roof will be below the mountains in the background.

so i'll pick a focal length depending on which of the three scenarios i want to go with, generally shooting with the roofline running along the mountains isn't a good idea so i'll either shoot it wide and make the house bigger in the scene or compress the scene using a telephoto lens to show the grandeur of the mountains behind the house.
 

smoke665

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i generally view focal lengths as a tool to achieve a certain perspective.

I think you meant FOV not perspective. Perspective is the sense of depth or spatial relationship between objects in a photo. I would agree that focal length is a tool, but there's more to it than just FOV. Using a 20mm lens up close on a portrait is not going to be attractive, not only will there be distortion of facial features but the DOF increases, meaning you lessen the ability to blur the background. Conversely a portrait at 200mm gives a better rendering of the subject and compresses the background making those blurry backgrounds creamy smooth. Ideally many find 85mm the best for portrait on a crop sensor, but I prefer either my 100mm f2.8, a legacy 135mm f2.8, or the 70-200mm f2.8 on the full frame.
 

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