Lens Question

J

John M

Active member
This question will probably sound silly to all those who actually understand lenses, but as I'm new to this whole thing here it goes:

Would the Rebel T2I's kit lens set to a focal length of "50mm" be the same as using a Canon 50mm 1.8 II. It's my understanding that they would be different because of the fact that the 50mm 1.8 is meant for a full frame sensor. I recently, however, came across some conflicting information and need this straightened out for me.

Thanks for the help guys. Have a nice night.
 
It's because the 50mm f/1.8 is a pretty fast lens. It's 5 times faster then a kit lens at f/5.6. If used at the same aperture setting, the 50mm will be ALOT sharper and the 50mm f/1.8 also gives you the low-light option and shallower depth of field
 
John M said:
This question will probably sound silly to all those who actually understand lenses, but as I'm new to this whole thing here it goes:

Would the Rebel T2I's kit lens set to a focal length of "50mm" be the same as using a Canon 50mm 1.8 II. It's my understanding that they would be different because of the fact that the 50mm 1.8 is meant for a full frame sensor. I recently, however, came across some conflicting information and need this straightened out for me.

Thanks for the help guys. Have a nice night.
Click to expand...


No. First of all the 50mm 1.8 delivers a sharper image than the kit lens. Second the 50mm 1.8 is a faster lens, meaning the 1.8 allows you to shoot with less light as the kit lens would be 5.6 which is a HUGE difference.

At the end of the day though, the kit lens is only $100 and the Canon 50mm 1.8 is only $100 as well. These are two lenses imo which everyone shall own.

Take your time and read, after a while it well all make sense ......
 
They'll give the same fov, providing the zoom is actually set to 50 mm. DoF at full aperture will of course differ, but set to the same aperture, they will give exactly the same FoV and DoF.
Optically, the 50 1.8 will give a much cleaner image.
Dave
 
Cool guys. Thanks. While I understand everything that was just said regarding aperture and depth of field, my next question is this:

So my sensor has a crop factor of 1.6 right? Meaning that the 50mm 1.8 really appears to look more like an 80mm lens when taking photos with it right? What I'm hearing right now is you need to apply the crop factor to lenses that are meant for full frame cameras (the 50mm 1.8) and lenses that are built for APS-C sized sensors (18-55mm Kit Lens). Is this correct?

Thanks again for the help.
 
A 1.6 crop body's sensor crops out the image's exterior when used with a lens made for full frame. So yes, the type of lens needs to be considered.
 
It's all confusing at first, but try to think of it this way: The difference in focal length happens because of the camera body, not because of the lens. So if you want to put a lens on a 7D, multiply the FOV (50mm in this instance) by 1.6. On a 5D (which is full frame) it would be 50mm. Now some lenses are meant only for sensors that crop (APS-C for Canon), so they won't work on a 5d. However, nothing changes in the FOV measurements. You still multiply by 1.6 for those lenses.
 
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