I need help understanding what I did...

[KGPhotography]

I was toying around with two lenses, A Sigma 50mm f/2.8 and a Sigma 50mm f/1.4 - I took two pictures using the same settings and distance, but just different lenses. Each has a 75mm focal point, but I get two different images and I want to understand why...

Thanks

50mm f/2.8: Taken with a Sigma 50mm f/2.8 Lens | Flickr - Photo Sharing!
50mm f/1.4: Taken with a Sigma 50mm f/1.4 Lens | Flickr - Photo Sharing!

Thanks again.
Kimberly

[3bayjunkie]

the 50mm 2.8 is a macro lens its made for doing close up shots. the 1.4 is a normal portrait lens.

[Niresangwa]

The FoV is different thanks to the lens construction, therefore how the light hits the sensor gives a wider angle of view.

[BryanC]

The specs for the 50mm 1.4 show it being a 75mm equivalent on a 1.5 crop sensor.

The specs for the 50mm 2.8 show it being an 85mm equivalent on a 1.5 crop sensor.

[BigFuzzy]

Originally Posted by Niresangwa

The FoV is different thanks to the lens construction, therefore how the light hits the sensor gives a wider angle of view.

Originally Posted by BryanC

The specs for the 50mm 1.4 show it being a 75mm equivalent on a 1.5 crop sensor.
The specs for the 50mm 2.8 show it being an 85mm equivalent on a 1.5 crop sensor.

Thank you... I'd had someone ask me this exact question and haven't had a chance to find out the answers.. I'd have never known that two 50mm (regardless of f/#) could have different FoV. Wow. Seems kind of.. well.. wrong.

[mshockley]

One of the best questions and most informative answers of all time! I had no idea this could be like this.

It also makes me think about a few things: Without seeing the pictures I would have said the 50mmf/1.4 is the lens I want! After viewing the pictures, I most definitely prefer the one using the 50mmf/2.8!

So now what I would like to see is the same experiment done with say a head/shoulders portrait shot??

It makes you stop and really think about what you want in a lens.......

[mshockley]

Originally Posted by BryanC

The specs for the 50mm 1.4 show it being a 75mm equivalent on a 1.5 crop sensor.

The specs for the 50mm 2.8 show it being an 85mm equivalent on a 1.5 crop sensor.

At the risk of sounding like an indiot, where do you find this information? Is it on the box?

[SwissJon]

The focal length given on a lens is the focal length at infinity, close focal points give different focal lengths depending on the structure of the glass inside, caused by focus breathing (IF lenses are much more prone to focus breathing)

[OsmosisStudios]

Originally Posted by SwissJon

The focal length given on a lens is the focal length at infinity, close focal points give different focal lengths depending on the structure of the glass inside, caused by focus breathing (IF lenses are much more prone to focus breathing)

... and exacerbated by the fact that one lens is a macro, which is designed specifically for this kind of shot.

Shoot something at about 5 ft with both lenses.

[RLucas]

Originally Posted by SwissJon

The focal length given on a lens is the focal length at infinity, close focal points give different focal lengths depending on the structure of the glass inside, caused by focus breathing (IF lenses are much more prone to focus breathing)

Originally Posted by OsmosisStudios

... and exacerbated by the fact that one lens is a macro, which is designed specifically for this kind of shot.

Shoot something at about 5 ft with both lenses.

Thanks guys! I actually learned something today.