Full-frame and Crop-sensor... is a 50mm really a 75mm?

[TimBrandt]

So... I was wondering if a 50mm on a crop-sensor really is equivalent to a 75mm on a Nikon full-frame?

Here's my trail of thought... if we for the sake of argument presume that 85mm is the best for portraits (no need to discuss that now), and shooting with a 50mm on a Nikon crop-sensor camera is equal to 75mm... is that really how it is then? I mean it's called crop-sensor not zoom-sensor right? There is a technical differences between a 75/85mm lens and a 50mm lens, and if the sensor-to-subject distance is the same, and the image of the crop-sensor is 'cropped' to be equal to a 75mm, I would think... that that would mean... that because of the difference in the lenses and the sensor-to-subject distance and just because the two lenses compresses the image differently because of the difference in mm, you can't really call a 50mm on a crop-sensor a 75mm?

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame? Presuming of course that the sensor and camera themselves produce the same quality picture.

 

[Serickmetz]

It will look like the focal length of 75mm on a full frame but there's going to be a lot more differences in your images coming from crop and full frame sensors, like DoF n such

 

[Remeniz]

The focal hasn't changed. It's still a 50mm. It's just that the 50mm film lens on a crop sensor will give a field of view equivalent to a 75mm on a full frame sensor.

 

[TimBrandt]

It will look like the focal length of 75mm on a full frame but there's going to be a lot more differences in your images coming from crop and full frame sensors, like DoF n such

That is kind of what I was after. Again presuming that 85mm is optimal for portraits (and all I shoot is pretty much portraits), then while shooting with a crop-sensor and a 50mm, I won't get the same look as a 75mm on a full-frame because like you said... DoF and such... which is very important. The crop is irrelevant as I can just take a step closer to the model (zoom with your feet ftw). It's the DoF and the appearance of the face that is important.

Of course I could just get a 85mm on a crop sensor to get the same look, but I was curious about this.

 

[TimBrandt]

The focal hasn't changed. It's still a 50mm. It's just that the 50mm film lens on a crop sensor will give a field of view equivalent to a 75mm on a full frame sensor.

Yeah that was what I was thinking... I just got confused from the whole "is equal too" thing

 

[BarnET]

So... I was wondering if a 50mm on a crop-sensor really is equivalent to a 75mm on a Nikon full-frame?

Here's my trail of thought... if we for the sake of argument presume that 85mm is the best for portraits (no need to discuss that now), and shooting with a 50mm on a Nikon crop-sensor camera is equal to 75mm... is that really how it is then? I mean it's called crop-sensor not zoom-sensor right? There is a technical differences between a 75/85mm lens and a 50mm lens, and if the sensor-to-subject distance is the same, and the image of the crop-sensor is 'cropped' to be equal to a 75mm, I would think... that that would mean... that because of the difference in the lenses and the sensor-to-subject distance and just because the two lenses compresses the image differently because of the difference in mm, you can't really call a 50mm on a crop-sensor a 75mm?

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame? Presuming of course that the sensor and camera themselves produce the same quality picture.

Well your field of view is the same. So you will include the same amount of your surroundings behind your subject. So in that regard the image looks the same.

The narrower field of view causes the compression. So in that regard they look the same. Just crop an image you have and you will see the same effect.

But be aware the DOF equiv. Is also multiplied. So it really looks like an 75mm f2.8ish. An fullframe let's you isolate your subject more with an 85mm (don't know any 75mm).

Besides that 50mm lenses do NOT create the nice bokeh the 85mm have. They tend to be a bit more nervous.

Still for an beginner 50mm f1.8 lenses can be great for experimenting with depth of field. There have been many great portraits taken with them in the real world.

 

[darklamp]

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame?

For the same focus distance and the same aperture ( f-number ) the field of view will be the same, but the depth of field will be different.

 

[John Deerfield]

The narrower field of view causes the compression. So in that regard they look the same. Just crop an image you have and you will see the same effect.

This is incorrect. Distance determines perspective ("compression"), not FoV.

Besides that 50mm lenses do NOT create the nice bokeh the 85mm have. They tend to be a bit more nervous.

That is rather a broad statement. There are plenty of 50mm lenses that have astounding bokeh. And there are 85mm lenses that don't. It really depends on the lens.

For the OP, I know of several photographers who wish "equivalents" didn't exist. Will there be an aesthetic difference between 50mm DX and 75mm FX? Yes. Will it be extreme? No.

 

[D00M]

Hi OP: Technical definition, yes.

50mm or 75mm is parameter to define the focal length. Which is independent of sensor size.

Then due to different sensor size, equivalence is used to define comparable field of view (or angle of view). So yes, 50mm on ASP-C sensor (Nikon's 1.5x) has equivalent field of view (or angle of view) as 75mm on full frame sensor.

On the other hand, as John mentioned, this doesn't measure any potential aesthetic differences.

 

[dsjtecserv]

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame?

For the same focus distance and the same aperture ( f-number ) the field of view will be the same, but the depth of field will be different.

Or, to add another option to the mix:

As darklamp says, assuming you shoot from the same position, with the same distance to the subject in both cases, then the framing and the perspective ("compression"; relative size and position of objects in the frame) will be the same. If you use the same aperture, the full frame version will have less depth of field. However, if you increase the f-number by the same crop factor (1.5 in the case of Nikon, so if you shoot at f/8 with the crop you would use f/12 with the full frame), the depth of field will also be essentially the same in both cases. To produce the same exposure you would need to increase shutter speed by the crop factor squared (about 2.25 for a 1.5 crop factor). Or you could maintain the same shutter speed and increase ISO by the same factor.

If you did any of these you would have images that are equivalent in all significant respects with both systems.

Dave

 

[TimBrandt]

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame?

For the same focus distance and the same aperture ( f-number ) the field of view will be the same, but the depth of field will be different.

Or, to add another option to the mix:

As darklamp says, assuming you shoot from the same position, with the same distance to the subject in both cases, then the framing and the perspective ("compression"; relative size and position of objects in the frame) will be the same. If you use the same aperture, the full frame version will have less depth of field. However, if you increase the f-number by the same crop factor (1.5 in the case of Nikon, so if you shoot at f/8 with the crop you would use f/12 with the full frame), the depth of field will also be essentially the same in both cases. To produce the same exposure you would need to increase shutter speed by the crop factor squared (about 2.25 for a 1.5 crop factor). Or you could maintain the same shutter speed and increase ISO by the same factor.

If you did any of these you would have images that are equivalent in all significant respects with both systems.

Dave

 

[TimBrandt]

Today I shoot with a Nikon D80 and a Nikon 50mm f/1.8G. I've been wanting to upgrade to a Nikon D3300 simply for the higher resolution and image quality, and better ISO performance. Now I'm considering upgrading my 50mm to the Nikon 85mm f/1.8G and wait to upgrade my camera, because I think the 85mm will give me a better compression for the portraits I shoot.




Copyright 2014 . Tim Brandt Photography

 

[dsjtecserv]

What I'm basically getting at is this... will a 50mm on a crop-sensor look exactly like a 75mm on a full-frame?

For the same focus distance and the same aperture ( f-number ) the field of view will be the same, but the depth of field will be different.

Or, to add another option to the mix:

As darklamp says, assuming you shoot from the same position, with the same distance to the subject in both cases, then the framing and the perspective ("compression"; relative size and position of objects in the frame) will be the same. If you use the same aperture, the full frame version will have less depth of field. However, if you increase the f-number by the same crop factor (1.5 in the case of Nikon, so if you shoot at f/8 with the crop you would use f/12 with the full frame), the depth of field will also be essentially the same in both cases. To produce the same exposure you would need to increase shutter speed by the crop factor squared (about 2.25 for a 1.5 crop factor). Or you could maintain the same shutter speed and increase ISO by the same factor.

If you did any of these you would have images that are equivalent in all significant respects with both systems.

Dave

 

[Leonard Migliore]

Today I shoot with a Nikon D80 and a Nikon 50mm f/1.8G. I've been wanting to upgrade to a Nikon D3300 simply for the higher resolution and image quality, and better ISO performance. Now I'm considering upgrading my 50mm to the Nikon 85mm f/1.8G and wait to upgrade my camera, because I think the 85mm will give me a better compression for the portraits I shoot.

The 85mm f/1.8 is a terrific portrait lens for DX. You'll have to back off a bit from the subject, which will give you greater compression than with the 50 but I find the effect to be very flattering.

 

[chris102]

Today I shoot with a Nikon D80 and a Nikon 50mm f/1.8G. I've been wanting to upgrade to a Nikon D3300 simply for the higher resolution and image quality, and better ISO performance. Now I'm considering upgrading my 50mm to the Nikon 85mm f/1.8G and wait to upgrade my camera, because I think the 85mm will give me a better compression for the portraits I shoot.


Copyright 2014 . Tim Brandt Photography

It SEEMS like a longer lens gives you more compression only because you need to get further away to make the subject the same size. If you use an 85mm lens on medium format and get in close, it will have a similar perspective and field of view as a 50mm on an FX camera.

--

http://101-365.com/

 

[Tom_N]

The crop is irrelevant as I can just take a step closer to the model (zoom with your feet ftw). It's the DoF and the appearance of the face that is important.

Changing the camera-subject distance ("zooming with your feet") will change perspective, which will change the appearance of the face, perhaps a lot more than the DoF changes will.

 

[TimBrandt]

The crop is irrelevant as I can just take a step closer to the model (zoom with your feet ftw). It's the DoF and the appearance of the face that is important.

Changing the camera-subject distance ("zooming with your feet") will change perspective, which will change the appearance of the face, perhaps a lot more than the DoF changes will.

But then I would have to step back and then the framing would be off from what I want, and I would have to crop the image in post, which I really don't want to do. I would also presume that the DoF would change too. I think that's why I feel that an 85mm is perfect for me, although the 50mm does a great job. Love that lens

 

[TimBrandt]

Today I shoot with a Nikon D80 and a Nikon 50mm f/1.8G. I've been wanting to upgrade to a Nikon D3300 simply for the higher resolution and image quality, and better ISO performance. Now I'm considering upgrading my 50mm to the Nikon 85mm f/1.8G and wait to upgrade my camera, because I think the 85mm will give me a better compression for the portraits I shoot.

The 85mm f/1.8 is a terrific portrait lens for DX. You'll have to back off a bit from the subject, which will give you greater compression than with the 50 but I find the effect to be very flattering.

 

[TimBrandt]

Today I shoot with a Nikon D80 and a Nikon 50mm f/1.8G. I've been wanting to upgrade to a Nikon D3300 simply for the higher resolution and image quality, and better ISO performance. Now I'm considering upgrading my 50mm to the Nikon 85mm f/1.8G and wait to upgrade my camera, because I think the 85mm will give me a better compression for the portraits I shoot.


Copyright 2014 . Tim Brandt Photography

It SEEMS like a longer lens gives you more compression only because you need to get further away to make the subject the same size. If you use an 85mm lens on medium format and get in close, it will have a similar perspective and field of view as a 50mm on an FX camera.

--
http://101-365.com/

Really? Crop+85mm vs full+50mm?

 

[darklamp]

Just an alternative suggestion for a lens.

It's not as fast as an f1.8, but the Tamron 90mm f2.8 is a very similar focal length and give you a great macro lens as well. I'm not a big fan of extremely narrow depth of field and really at 90mm on crop frame the f2.8 is narrow enough DOF for me. The bokeh is very nice.