MikeC82
I have a Canon HV40 video camera with a 10x optical lens. I am considering selling this and buying a Canon T2i photo camera, which comes with a 18-55mm lens. I'm having a hard time figuring out a way to compare the lens zoom of the two. I know the 10x would be more powerful, but how do I figure out what 35mm equivalent I would need to be at least as much or more as a 10x optical lens for a video camera?
So I'd need to buy a 436mm lens equivalent for my T2i to match the 10x optical zoom of the video camera? Wow, that's much more than I thought (or can afford).
Answer
Cameras are different and there is no universal one to one correspondence between magnification and focal length of lens. It depends mostly on the size of the light sensor. Small point & shoot cameras have small sensors, therefore they do not need a lot of lens extension to get to the higher magnification. Mid range DSLR's have sensors about 66% of a 35mm film frame, the best DSLR's have a sensor the same size as a 35mm film frame. The trade-off is noise...small point & shoot sensors will start getting noisy at anything over 100 ISO. The good Canon & Nikons with the full frame sensor still do a decent job with noise up to 3200 ISO.
Cameras are different and there is no universal one to one correspondence between magnification and focal length of lens. It depends mostly on the size of the light sensor. Small point & shoot cameras have small sensors, therefore they do not need a lot of lens extension to get to the higher magnification. Mid range DSLR's have sensors about 66% of a 35mm film frame, the best DSLR's have a sensor the same size as a 35mm film frame. The trade-off is noise...small point & shoot sensors will start getting noisy at anything over 100 ISO. The good Canon & Nikons with the full frame sensor still do a decent job with noise up to 3200 ISO.
How do I work out the magnification of a zoom lens for a DSLR?
mouse_spin
I recently got a Canon EOS 400D digital SLR camera and I am looking to upgrade the lens for one with a more powerful zoom. However separate lenses are new to me so I am struggling to figure out which lenses are more powerful than others.
I was hoping someone would be able to tell me how you can either work out the strength of the optical zoom on Canon lenses, or give me suggestions of lenses to look at.
Any help is greatly appreciated.
Many thanks,
Martin.
Answer
You already have two excellent answers, but I have this one in the can at all times, so here you go. My answer adds a little visual aid.
There is not a lens-to-distance equation. If we are talking about a "35 mm equivalent," a 50 mm focal length is approximately "normal" view without any magnification. For most DSLR's, the lens factor of 1.5-1.6 means a "normal" focal length would be about 31-33 mm. If we go back to a 50 mm "normal" lens then, a 100 mm lens would be a "2 power" lens, 200 mm would be 4X, and so on.
Just divide the smaller number into the bigger number and you get the "X" power of the lens. For instance, a 35-80 mm lens is 2.3X zoom. Divide 80 by 35 and you'll get the result. 35-80 mm lens is 2.3X zoom. Divide 80 by 35 and you'll get the result.
It is usually better to know what the focal length of a lens in "35 mm equivalent" is and judge by that, rather than relying on the "X" power of the lens. For instance, most point and shoot cameras start at about 35 mm and have either a 3X or 4X zoom. This would make it a 35-105 or a 35-140. I've seen some that start at 28 mm, though. A 3X starting at 28 mm is 28-84 and a 4X is 28-112. Neither one is a particularly strong telephoto lens and the 4X is just about the same as the 3X that starts out at 35 mm.
It's also important to realize that tradition dictates that lens focal lengths are usually expressed in terms of "35 mm equivalent," where "35 mm" refers to a 35 mm film camera. This is because of the relation between the sensor size and the actual focal length of the lens and the resultant angle of view of the lens.
I have one point & shoot that is actually a 5.8-24 mm zoom. This is a 4X zoom. The 35 mm equivalent is 28-116 mm. The sensor is 7.2x5.3 mm. (1/1.8") (And I wish I knew someone who could explain how the heck they came up with sensor size terminology!)
I have another point & shoot that is actually a 5.7-17.1 mm zoom. This is a 3X zoom. The 35 mm equivalent is 34-102 mm. "How could a shorter focal length give a longer 35 mm equivalent?" you might ask. It's because the sensor is only about 5x4 mm. (1/2.5")
I have a few Nikon DSLR's and - thankfully - they all have the same size sensor. They all have a "lens factor" of 1.5. This means that you just multiply the actual focal length of the lens to get the 35 mm equivalent and then you can make comparisons accurately from camera-to-camera. Most Canon's, for instance, have a lens factor of 1.6. On a Nikon DSLR, a 28 mm lens is the "35 mm equivalent" of a 42 mm lens. On most Canon DSLR's, the same 28 mm lens is the equivalent of a 45 mm lens.
These example are just to show you how freaking confusing it can all become if you try to make sense of the "X" power of a zoom lens.
Bottom line...
Check the 35 mm equivalent specifications for the lens. This way, you will be leveling the field and comparing apples to apples. More or less.
Here is a mini-tutorial I made myself to compare focal lengths. This is NOT a lens test or a camera test! It is merely intended to show the difference between various focal lengths. The lens was the Nikon 18-200 VR lens, which is (by definition) an 11X lens, but that 11X does not tell you what the final image will look like. I added one more frame taken with a 300 mm lens. The camera was a Nikon D200 so there is a 1.5X "crop factor," "lens factor," or "focal length multiplier." There is further explanation on the image itself. It would help if you click on "All Sizes" above the image.
http://www.flickr.com/photos/7189769@N04/476181737/
This was done with two different lenses: the Nikon 17-55 and 70-300:
http://www.flickr.com/photos/samfeinstein/1245831147/
You already have two excellent answers, but I have this one in the can at all times, so here you go. My answer adds a little visual aid.
There is not a lens-to-distance equation. If we are talking about a "35 mm equivalent," a 50 mm focal length is approximately "normal" view without any magnification. For most DSLR's, the lens factor of 1.5-1.6 means a "normal" focal length would be about 31-33 mm. If we go back to a 50 mm "normal" lens then, a 100 mm lens would be a "2 power" lens, 200 mm would be 4X, and so on.
Just divide the smaller number into the bigger number and you get the "X" power of the lens. For instance, a 35-80 mm lens is 2.3X zoom. Divide 80 by 35 and you'll get the result. 35-80 mm lens is 2.3X zoom. Divide 80 by 35 and you'll get the result.
It is usually better to know what the focal length of a lens in "35 mm equivalent" is and judge by that, rather than relying on the "X" power of the lens. For instance, most point and shoot cameras start at about 35 mm and have either a 3X or 4X zoom. This would make it a 35-105 or a 35-140. I've seen some that start at 28 mm, though. A 3X starting at 28 mm is 28-84 and a 4X is 28-112. Neither one is a particularly strong telephoto lens and the 4X is just about the same as the 3X that starts out at 35 mm.
It's also important to realize that tradition dictates that lens focal lengths are usually expressed in terms of "35 mm equivalent," where "35 mm" refers to a 35 mm film camera. This is because of the relation between the sensor size and the actual focal length of the lens and the resultant angle of view of the lens.
I have one point & shoot that is actually a 5.8-24 mm zoom. This is a 4X zoom. The 35 mm equivalent is 28-116 mm. The sensor is 7.2x5.3 mm. (1/1.8") (And I wish I knew someone who could explain how the heck they came up with sensor size terminology!)
I have another point & shoot that is actually a 5.7-17.1 mm zoom. This is a 3X zoom. The 35 mm equivalent is 34-102 mm. "How could a shorter focal length give a longer 35 mm equivalent?" you might ask. It's because the sensor is only about 5x4 mm. (1/2.5")
I have a few Nikon DSLR's and - thankfully - they all have the same size sensor. They all have a "lens factor" of 1.5. This means that you just multiply the actual focal length of the lens to get the 35 mm equivalent and then you can make comparisons accurately from camera-to-camera. Most Canon's, for instance, have a lens factor of 1.6. On a Nikon DSLR, a 28 mm lens is the "35 mm equivalent" of a 42 mm lens. On most Canon DSLR's, the same 28 mm lens is the equivalent of a 45 mm lens.
These example are just to show you how freaking confusing it can all become if you try to make sense of the "X" power of a zoom lens.
Bottom line...
Check the 35 mm equivalent specifications for the lens. This way, you will be leveling the field and comparing apples to apples. More or less.
Here is a mini-tutorial I made myself to compare focal lengths. This is NOT a lens test or a camera test! It is merely intended to show the difference between various focal lengths. The lens was the Nikon 18-200 VR lens, which is (by definition) an 11X lens, but that 11X does not tell you what the final image will look like. I added one more frame taken with a 300 mm lens. The camera was a Nikon D200 so there is a 1.5X "crop factor," "lens factor," or "focal length multiplier." There is further explanation on the image itself. It would help if you click on "All Sizes" above the image.
http://www.flickr.com/photos/7189769@N04/476181737/
This was done with two different lenses: the Nikon 17-55 and 70-300:
http://www.flickr.com/photos/samfeinstein/1245831147/
Powered by Yahoo! Answers
Tidak ada komentar:
Posting Komentar