A really noob question about focal length.

[rhino123]

I have a really noob question (idiotic even) but it had been bothering me for a while now...

Okay. Now, I know I didn't have the budget for a 500mm lens, but I have a 300mm + 1.4TC do the focal lenght is 420mm.

So if I took a step forward from point A to point B, and lets say the step is 80mm total, then shoot the picture. Is that equivalent to shooting a subject in point A with a 500mm lens?

 

[tirediron]

For all intents and purposes, it should be, yes.

 

[o hey tyler]

I have a really noob question (idiotic even) but it had been bothering me for a while now...

Okay. Now, I know I didn't have the budget for a 500mm lens, but I have a 300mm + 1.4TC do the focal lenght is 420mm.

So if I took a step forward from point A to point B, and lets say the step is 80mm total, then shoot the picture. Is that equivalent to shooting a subject in point A with a 500mm lens?

Your FoV using the 300mm + 1.4x TC is over 500mm unless you're using a Full frame camera.

 

[Big Mike]

Your FoV using the 300mm + 1.4x TC is over 500mm unless you're using a Full frame camera.

Field of view isn't directly related by a focal length because there are different formats (sensor sizes etc). So saying that the FOV is over 500mm is misleading.
I've said it a million times...but the crop factor only comes into play when you are comparing something to the 35mm film format. If someone only has their digital camera, and isn't used to using a 35mm film camera...then the crop factor shouldn't even be brought up.

They are asking about getting to 500mm on their camera.

 

[o hey tyler]

Your FoV using the 300mm + 1.4x TC is over 500mm unless you're using a Full frame camera.

Field of view isn't directly related by a focal length because there are different formats (sensor sizes etc). So saying that the FOV is over 500mm is misleading.
I've said it a million times...but the crop factor only comes into play when you are comparing something to the 35mm film format. If someone only has their digital camera, and isn't used to using a 35mm film camera...then the crop factor shouldn't even be brought up.

They are asking about getting to 500mm on their camera.

They're asking about relative figures though. If they take a step towards their subject (80mm worth of distance) it would still not be "equivalent" to shooting a 500mm lens. At least in my eyes. It would be shooting with a <500mm lens at a closer distance. If they understand that they're shooting with a cropped body (assuming they are), then they should also understand that they effectively have greater than a 500mm FoV, yes?

 

[Robin Usagani]

No. The subject will be almost the same, but you will get more of the background (wider angle) behind the subject if you walk closer.

I have a really noob question (idiotic even) but it had been bothering me for a while now...

Okay. Now, I know I didn't have the budget for a 500mm lens, but I have a 300mm + 1.4TC do the focal lenght is 420mm.

So if I took a step forward from point A to point B, and lets say the step is 80mm total, then shoot the picture. Is that equivalent to shooting a subject in point A with a 500mm lens?

 

[Big Mike]

then they should also understand that they effectively have greater than a 500mm FoV, yes?

You are making the assumption that a '500mm FOV' on a 35mm camera is the only 500mm FOV...and that they 'effectively' have a greater (narrower) FOV.
But really, the only FOV that matters is the one they get with their camera....there is no 'effectively'....and I just think that it's confusing to bring it up.

Now, if someone had said "I've been shooting with a 35mm film camera and a 500mm lens, but now I'm shooting with a Digital Rebel and the same 500mm lens...why is my FOV different"....then you would bring up the crop factor and how it affects DOF (and how it doesn't actually change the focal length).

They're asking about relative figures though. If they take a step towards their subject (80mm worth of distance) it would still not be "equivalent" to shooting a 500mm lens. At least in my eyes. It would be shooting with a <500mm lens at a closer distance.

I agree with you here.

 

[o hey tyler]

Okay, I see what you're saying now. :thumbup:

 

[Bitter Jeweler]

Making a step forward, would be more than 80mm. Thats 8cm. The step forward does not change the focal length of the lens.

That's like taking a 50mm lens and saying stepping 450mm, 45cm, which is about a foot and a half, would give you the same focal length of a 500mm lens.

 

[Robin Usagani]

Making a step forward, would be more than 80mm. Thats 8cm. The step forward does not change the focal length of the lens.

That's like taking a 50mm lens and saying stepping 450mm, 45cm, which is about a foot and a half, would give you the same focal length of a 500mm lens.

After reading the OP, maybe you are right LOL. I thought he was saying he will be walking forward 80mm zoom worth.

My point is, walking closer will never give you the same image as zooming closer. Unless you are taking a pic of a flat subject with no background that is farther away.

 

[Bitter Jeweler]

With similar focal lengths, you would be able to get very "nearly" the same image, by walking to or fro. I do think you could still get similar images from a 50mm as you could by a 100mm. You would be standing closer with the 50, and farther away with the 100. You should try it.

And walking closer won't give you "more background (wider angle) behind the subject", you would get less.

 

[Robin Usagani]

Hmmm, I thought this topic has been covered so many times?

Wide-angle lens - Wikipedia, the free encyclopedia

See the water bottle photos.

 

[Derrel]

300mm prime lens + TC 1.4x = pretty decent lens performance with a Nikon or Canon 300mm lens of modern design.

Angle of view of a 420mm setup on 35mm FF or digital FF = 4.9 degrees horizontal

Angle of view of a 500mm lens on a 35mm FF or digital FF = 4.1 degrees horizontal

That is a significantly narrower angle of view for the 500mm lens than merely stepping 80mm closer!!! http://www.canon.com/bctv/calculator/calculator1.html

 

[rhino123]

Okay, guys, thanks for all the replies and answer, I think I understand now... and yes... by moving forward for say 80mm it will still not amount to a 500mm lens when I was shooting at the original position.