Confusion with new lens

[ahansen60]

So if you have certain lens and put it on a FX camera and then a DX camera you will get two very different pictures correct? But it doesn't necessarily work the opposite way? If you take a certain camera and put an FX lens on it and then a DX lens you will get the same image each time? Am I understanding that correctly? Because FX and DX lenses produce the same size image circles?

 

[coastalconn]

That is correct. Any lens at 200mm (or any focal length) will be the same on a dx body....

 

[Dao]

So if you have certain lens and put it on a FX camera and then a DX camera you will get two very different pictures correct? But it doesn't necessarily work the opposite way? If you take a certain camera and put an FX lens on it and then a DX lens you will get the same image each time? Am I understanding that correctly? Because FX and DX lenses produce the same size image circles?

The FX lens will produce a larger image circle than the DX lens. If you are able to see the projected image on the sensor, you will notice the object size (i.e. a tea cup) in the images are the same (assume same focal length). But the image circle from the FX lens is larger. (like wider field of view)

 

[Patrice]

I wish there was a concise way to explain crop factor, but no matter how many times and how many different people attempt it, some folks are simply incapable of grasping the significance of it.

Crop factor in the context of FX vs DX only means something in terms of field of view on a displayed image at a fixed display dimension. It only really matters when you start using different format cameras. If you stick to DX then just ignore it. Learn to evaluate the various focal lengths in terms of the perspective and field of view they produce on your DX camera. Ignore DX/FX nomenclature, it means nothing in terms of what the size of an object will be in an image from your DX camera.

 

[ahansen60]

This is the reason behind my question:

 

[Dao]

And that is the reason why the manufacturer put that description. (To sell more)

 

[ahansen60]

Ok I think I finally have it figured out. Tell me if the following statement is true: An FX and DX lens of the same focal length will produce the same image on a DX body. But an FX and DX lens of the same focal length will produce different images on an FX body.

 

[CheezyCheeto]

No... Any Lens on any one camera body with the same focal length will have the same field of view, granted the dx lens may have vignetting on the fx body depending on the lens. its when you use a lens on a dx and then the same lens on the fx that the field of view looks different.

Like it was stated above, if you're only using dx, just stick with the numbers(focal lengths) and forget about all the crop factor stuff.

 

[manicmike]

If you want more reach I've got a 2x teleconverter for sale in the marketplace for $60 that came with my Sigma 80-400. It's a digital concepts (rebranded Tamron)

 

[Patrice]

Ok I think I finally have it figured out. Tell me if the following statement is true: An FX and DX lens of the same focal length will produce the same image on a DX body.

You got it!

But an FX and DX lens of the same focal length will produce different images on an FX body.

Put the DX lens on a FX camera and the size of the objects in the image will be the same as if a same focal length FX lens had been used. However the edges and corners of the frame will be black because the DX lens does not illuminate the full frame of an FX camera. The same thing would happen if I mounted an FX lens on a MF (medium format) camera. (That is if I could bring the image to focus.)

 

[Alan92RTTT]

But an FX and DX lens of the same focal length will produce different images on an FX body.

Put the DX lens on a FX camera and the size of the objects in the image will be the same as if a same focal length FX lens had been used. However the edges and corners of the frame will be black because the DX lens does not illuminate the full frame of an FX camera. The same thing would happen if I mounted an FX lens on a MF (medium format) camera. (That is if I could bring the image to focus.)

"edges and corners of the frame will be black" Which is a fancy way of saying the image will be different. Its easy to get hung up on small details when they are irrellivant.

It takes new DSLR owners a while to get the whole crop factor thing because of marketing and other things that new users just don't get yet.

I found it simple to look at it this way. If you have a DX body you can use FX or DX lenses. A 200mm FX lens and a 200mmDX lens will give you the same image on your DX body. If you plan to upgrade to a FX body buy FX lenses. If you have a 200mm lens and want to double your reach buy a 400mm lens. Don't worry about the "crop factor" issue as it just confuses things.