Crop sensors, Angle of view, Perspective and Portraits...

[Luigi_xp]

I was thinking on upgrading my gear, and buying a prime lens for portaits.
Then i did think something: When taking portraits, to mantain an great perspective, you need to use an mid-telephoto lens. I was thinking in getting an 85mm lens, but with a crop sensor, an 50mm is the closest match (50.1,6 canon = 80.)
But, thinking for some time, i did face an interesting question:
An APS-C sensor change the angle of view... But because the focal length is the same, Does it affect perspecive? As the crop sensor is just a "crop" on the center of the image, it shouldn't change perspective.
So, to have the same perspective as an 85mm lens on a full frame sensor, i use an 50mm on APS-C or an 85mm?
Thanks!

 

[480sparky]

A 50mm on a FF camera will have the same perspective as a 50mm on a crop body when they're the same distance from the subject.

But the perspective will change when you have to move back to get the same view with a crop body.

 

[lennon33x]

One thing to remember is that the shorter the focal length, the more distorted your subject becomes. I really enjoyed the field of view on my 50 on a crop, but when I switched to FF, the subjects became much more pleasing at 85.

Essentially the only similarity in calculating crop factor is field of view; perspective, working distance, light sensitivity, etc all change (to a degree)

 

[hirejn]

Obviously a 50 mm lens is not an 85. It's not built the same way, and on a Nikon DX it's only 75 mm angle of view, not 85, so it's not a replacement. It may be a decent simulation. I like the 50 1.8 on my DX because I can use it in tighter situations than the 70-200 and still get compression. However, it's not as good as the 85 1.4.

 

[Tinderbox (UK)]

Question : I have an micro 4:3 camera an Panasonic GX7 - the crop factor is 2x the lens i have is 14-42, so that`s gives an 28-84 aspect ratio , now if i take an head and shoulders should i shoot at 42/84 and if i am taking an head to toe i should shoot at 25/50 am i totally wrong or what.

thanks

John.

 

[lennon33x]

Question : I have an micro 4:3 camera an Panasonic GX7 - the crop factor is 2x the lens i have is 14-42, so that`s gives an 28-84 aspect ratio , now if i take an head and shoulders should i shoot at 42/84 and if i am taking an head to toe i should shoot at 25/50 am i totally wrong or what.

thanks

John.

Your crop factor is 2x the focal length; so yes, the theory is correct. A head/shoulders shot at a 42mm is going to cast a weird distortion of the subject. I'm not sure that I would personally do that. But the FoV should be similar.

You have to think about what you're going for in your composition. Is it really about what you can include in the image, or is it about the subject? If it's the former, go wider; if it's the latter, try a different approach (i.e. step back to include what you want at a more pleasing focal length and then crop in post).

 

[Tinderbox (UK)]

Thanks, it might only be 42mm but i will be standing farther back to get the same shot as a FF will that not reduce the distortion.

John.

Question : I have an micro 4:3 camera an Panasonic GX7 - the crop factor is 2x the lens i have is 14-42, so that`s gives an 28-84 aspect ratio , now if i take an head and shoulders should i shoot at 42/84 and if i am taking an head to toe i should shoot at 25/50 am i totally wrong or what.

thanks

John.

Your crop factor is 2x the focal length; so yes, the theory is correct. A head/shoulders shot at a 42mm is going to cast a weird distortion of the subject. I'm not sure that I would personally do that. But the FoV should be similar.

You have to think about what you're going for in your composition. Is it really about what you can include in the image, or is it about the subject? If it's the former, go wider; if it's the latter, try a different approach (i.e. step back to include what you want at a more pleasing focal length and then crop in post).

 

[NedM]

I was thinking on upgrading my gear, and buying a prime lens for portaits.
Then i did think something: When taking portraits, to mantain an great perspective, you need to use an mid-telephoto lens. I was thinking in getting an 85mm lens, but with a crop sensor, an 50mm is the closest match (50.1,6 canon = 80.)
But, thinking for some time, i did face an interesting question:
An APS-C sensor change the angle of view... But because the focal length is the same, Does it affect perspecive? As the crop sensor is just a "crop" on the center of the image, it shouldn't change perspective.
So, to have the same perspective as an 85mm lens on a full frame sensor, i use an 50mm on APS-C or an 85mm?
Thanks!

I own a 50mm f/1.8 II and also shoot on a 1.6 crop factor DSLR - so it roughly becomes an 80mm.
It is such a great focal length for portraits, and honestly I wouldn't trade that lens for the world!
Unless Canon came out with an IS version then that's a different story.

It doesn't necessarily change your perspective, just only crops what your DSLR can see. In this case, because you are shooting on a crop factor camera, you won't be able to see the full focal length of the 50mm.

 

[lennon33x]

I own a 50mm f/1.8 II and also shoot on a 1.6 crop factor DSLR - so it roughly becomes an 80mm. It is such a great focal length for portraits, and honestly I wouldn't trade that lens for the world! Unless Canon came out with an IS version then that's a different story. It doesn't necessarily change your perspective, just only crops what your DSLR can see. In this case, because you are shooting on a crop factor camera, you won't be able to see the full focal length of the 50mm.

I can't say I agree with you on this.

Here's why:

 

[Ysarex]

Thanks, it might only be 42mm but i will be standing farther back to get the same shot as a FF will that not reduce the distortion.

John.

Perspective is a function of where you put the camera period. Lens focal length does not determine perspective and different lens focal lengths do not have different perspectives. The only way to alter perspective is to pick up the camera and move it.

If you are using a smaller camera (m-4/3) rather than a FF but are standing farther from the subject you will get the perspective that comes from being farther back. Perspective is not distortion; it is simply perspective. In taking portraits it's common to select a perspective position far enough away from the subject so as to suppress the relative significance of variations in the 3D positions of the subject's features (nose versus ears for example). In other words back up. The choice of lens focal length frames the shot. It has no effect on perspective.

Joe

 

[Luigi_xp]

Thanks for all the responses, i will go with the 50mm.

 

[enzodm]

Kundalini did an excellent experiment:
http://www.thephotoforum.com/forum/...rence-between-full-frame-cropped-sensors.html

 

[Derrel]

Fashionista Stephen Eastwood did a series of lens focal length comparisons some years back. Here's a GOogle search result linking to it. These were shot on the Canon 1D something-or-other...the one with the 1.3x sensor,m the so-called APS-H sized sensor. Stephen Eastwood + lens focal length comparison series - Google Search

The focal lengths used range from 19mm, to 350mm. It's a terrible shame that the majority of links to this are now very low-resolution. This three-panel comparo shows a bit better. focallength_mini.jpg