FX lens on DX body

[sashbar]

...A 50 mm 1.4g lens on a Nikon with a crop factor of 1.5 will give you the same perspective as a 75 mm lens, it does not however truly change the focal length of the lens itself.

Really?
Ok, probably you mean that it will allow you keep the same distance as a 75 mm on FF..

 

[robbins.photo]

I have a question pertaining to the FX lenses on the DX bodies.

Don't do it. Your children will be born sterile.

If i were to get a 50mm 1.4g from nikon, that would be an equivalent to a 75mm on my DX camera. Would this lens choice make the 75mm a meaningless purchase? The 50mm 1.4g (75mm on dx body) coupled with the 35mm 1.8g would make a very good combo. Am i wrong about this?

Well, not quite actually. A 50 mm 1.4g lens on a Nikon with a crop factor of 1.5 will give you the same perspective as a 75 mm lens, it does not however truly change the focal length of the lens itself. Might be splitting hairs a bit but there is actually a difference. If you were to go with an 85 mm of course that would give you the same perspective as if the focal length were roughly 130 mm. So really it will just depend on what sort of focal lengths you think you'll need.

So its not really the same is what you're saying? Its not making any sense to me.

Ok.. let me see if I can simplify a little bit. Focal length (such as 50 mm, 85 mm, etc) is actually the distance between the lens and the image sensor when your subject is in focus. The angle of view is the amount of area you have in your image expressed as an angle. Now if you are using a zoom lens of some sort and you change your focal length, this also changes your angle of view. If you zoom in the angle gets smaller and the object your photographing appears "bigger". If you zoom out your angle gets wider, so you are getting more area in your photograph but individual objects appear smaller because your getting a wider angle of view.

The crop factor on a DX sensor does not actually change the focal length of the lens - what it actually does is change the angle of view. If your using an FX lens, your not actually using the entire lens on a DX body, only a portion in the center. This changes the angle of view - which does make the object your focusing on appear larger. It is not, however, actually changing the focal length of the lens.

So if your using a 50 mm lens on a DX body with a 1.5 crop factor, what you see and what the camera sees has the same "perspective" as what you would see using an 75 mm lens on an FX body. The crop factor is not changing the focal length, but because it is changing the angle of view what your seeing is the same as what you would see with an 75 mm lens on an FX body. It doesn't actually change the lens or focal length in any way, it merely appears the same as the 75 mm on FX because your not actually using the entire 50 mm lens, only a portion of it. That changes your angle, which makes things look bigger.

In practical purposes this is probably more detail than you really need, but unfortunately if you start discussing this subject in a public forum some yakadoodle always jumps all over you to impress everyone with his superior camera knowledge so I generally throw in the caveat to avoid that from happening.

 

[hamlet]

After investigating it for myself, i now understand why a fx 50mm isn't the same as a 75mm. It was a video made by Mike Browne where he explained how zoom lenses Affect photography. Basically all you need to understand is that: zooming is not the same as standing closer to your object.

 

[TheFantasticG]

I use the 50 1.4G on my D7k for portraits... and landscapes. I don't have any DX glass. Gave my dad the 35 1.8G DX I had. Thinking real had about getting that Sigma 18-35 1.8 though for nighscapes.

Not sure whats so hard to grasp about the DX/FX lens differences on each body... It was explained clearly in multiple ways by multiple people.

 

[hamlet]

Forgive me for my ignorance, i just can't get my head around their answers. Thank you everyone.

 

[robbins.photo]

Forgive me for my ignorance, i just can't get my head around their answers. Thank you everyone.

Apologies, gave it my best shot. It's kind of a strange topic to begin with and honestly probably not worth worrying about too much.

 

[robbins.photo]

...A 50 mm 1.4g lens on a Nikon with a crop factor of 1.5 will give you the same perspective as a 75 mm lens, it does not however truly change the focal length of the lens itself.

Really?
Ok, probably you mean that it will allow you keep the same distance as a 75 mm on FF..

Just trying to give the simplest explanation I possibly can - because frankly this always happens when this topic comes up and I think you can agree this really isn't helpful to the OP

 

[kundalini]

Forgive me for my ignorance, i just can't get my head around their answers. Thank you everyone.

If you've never shot with a film camera or a full frame digital camera before, the point is moot with regard to a discussion about FX versus DX. You will never know the difference until one of those other two criteria are met.

There is no harm using FX designated lenses for a DX camera. The DX lens line-up is not that old nor that diverse as the FX lenses.

 

[480sparky]

Maybe this will help.

 

[hamlet]

There is actually another difference that people are unaware of. You can easily figure it out by using your zoom lens vs standing closer physical to your subject. The difference will become all the more apparent to you if you do this trick with a bigger difference in zoom.

 

[PaulWog]

There is actually another difference that people are unaware of. You can easily figure it out by using your zoom lens vs standing closer physical to your subject. The difference will become all the more apparent to you if you do this trick with a bigger difference in zoom.

Are you trying to teach us about photography? We already know this.

 

[hamlet]

That's great champ.

 

[480sparky]

There is actually another difference that people are unaware of. You can easily figure it out by using your zoom lens vs standing closer physical to your subject. The difference will become all the more apparent to you if you do this trick with a bigger difference in zoom.

It's called zoom with your feet.

 

[Braineack]

Forgive me for my ignorance, i just can't get my head around their answers. Thank you everyone.

You have a 18-55. Set it to 50mm and now you know what an FX 50mm will look like on your body.

I've said this in one of your previous threads before...


I think the best example I can use to explain the crop factor is this:

Imagine you have a FF camera.

You take a beautiful shot of a landscape with your 50mm and have it printed at 11x14"

When you frame it, you matte it with an 8x10" matte.

Now pretend the full 11x14 print is the full frame sensor and the 8x10 matted crop is a crop sensor. That's the difference.

The reason people will say a 50mm on a crop-sensor is actually a 75mm is because they want to confuse you. All you are doing on a crop-sensor is capturing much less of the scene at the same exact focal length (50mm).

If you take the same example above, but used a 75mm lens on the FF camera when the picture was taken, it would be framed like the 8x10 matted crop, but now in the entire 11x14 size.

 

[480sparky]

...........The reason people will say a 50mm on a crop-sensor is actually a 75mm is because they want to confuse you...............

I don't think it has anything to do with wanting to confuse others. I think it's because they transpose the manufacturer's claim of "FOV equivilent to 75mm" as "50mm on a crop sensor is a 75mm lens" due to ignorance.