Difference in aperture and sensor size - anyone willing to help

[Overread]

Ok so I need someone to do be a favour here since I don't have the gear to test myself.

What I'd be interested in visually seeing is the difference in background blurring between a fullframe camera with a 135mm f2 lens and a crop sensor shot at f2.8 over the same focal length whilst taken in the same physical position of the same subject.

One thing that is plaguing me in some of the equine photography I'm doing is that the background, its full of distracting elements that are very hard to avoid in the setting (esp indoors). So I'm wondering if a shift in equipment might give at least a more pleasing result over what one might consider a typical arena. I'd rather not sit for hours making masks and using selective blurring to enhance what my shot already has and would rather get it in camera (because that takes seconds - whilst the editing could take ages).

If anyone has done this (or similar) I'd be eager to hear of your real world experiences and if you found any difference worth noting.

 

[480sparky]

Not too many 135/2 lenses floating around.

 

[Braineack]

you looking for something like this: full-frame vs crop-sensor comparison depth-of-field perspective - Tangents

There's a decent formula you can use that can calculate the "aperture" equivalent, it's only in terms of DOF and not light, but it's pretty close.

So if N = f / d where N = f-stop, f = focal length, and d = diameter of aperture.

Then to find the "equivalent" of a crop sensor, you add in the crop factor where:
N = (f x crop factor) / d

Say you had a 100mm lens at f/4 the aperture diameter is 25mm.
f/4 = 100 / 25

But the DOF of that same lens at f/4 on a crop sensor might look closer to it on a FF at f/6.
f/6 = (100 x 1.5) / 25

 

[runnah]

Not too many 135/2 lenses floating around.

Maybe not for nikons...

 

[480sparky]

Not too many 135/2 lenses floating around.

Maybe not for nikons...

Maybe not for most people with average disposable incomes.

 

[runnah]

Not too many 135/2 lenses floating around.

Maybe not for nikons...

Maybe not for most people with average disposable incomes.

It's not "that" expensive.

 

[Trever1t]

I have a 135DCf2 lens. I'm not quite sure I understand your confusion? The FF camera is going to give more OOF than a DX body using the same focal length IF the frame is the same. So with a DX you'll need to be further from your subject and vice versa. Ya?

 

[480sparky]

It's not "that" expensive.

Then buy me one.

 

[runnah]

It's not "that" expensive.

Then buy me one.

Trade you for a drone.

 

[Trever1t]

What I'd be interested in visually seeing is the difference in background blurring between a fullframe camera with a 135mm f2 lens and a crop sensor shot at f2.8 over the same focal length whilst taken in the same physical position of the same subject.

OK a FX and DX both shooting from mounts equidistant to the subject with the same focal length and aperture.....brain teaser.... the bokeh is the same. Only the FOV changes.

FX would allow you to get closer, if you could, thereby making for a shallower DOF and increased OOF elements given the subject to background distance remains the same. Right?

 

[photoguy99]

Not quite. You have to tell me if you're enlarging the two prints to the same size or not. If you leave the prints proportionately sized then yes. We're literally looking at the middle part of the same print.

If you're enlarging the smaller sensor image you the same print size, the bokeh will enlarge too.

 

[Trever1t]

you mean, if he enlarges the image from the FF sensor, since that one will be smaller in the frame due to the wider FOV...the FF enlarged then would have a more blurred background.

Would be the same result as having been closer with the FF sensor to have the same frame as the Crop sensor.

 

[photoguy99]

No, what I mean is if he enlarges the smaller one to the same size as the bigger one.

If you enlarge the two resulting files to, say, eight inches on the long side, the DX sensor will exhibit less DOF. Which is the opposite if the result you'd expect if you follow the rule of thumb.

If you enlarge the FF file to eight inches on the long side and the DX to 5.7 then the bokeh and everything else should look pretty much identical. The DX print will look like you just chopped the middle out of the FF one. Which is what you did, basically. This, I think, is what you're talking about in your post about same bokeh?

Overread needs to get real specific about the shots he wants taken. I can't make head or tails out of the OP.

 

[480sparky]

Trade you for a drone.

You first.

 

[Trever1t]

If you enlarge the FF file to eight inches on the long side and the DX to 5.7 then the bokeh and everything else should look pretty much identical. The DX print will look like you just chopped the middle out of the FF one. Which is what you did, basically. This, I think, is what you're talking about in your post about same bokeh?

Overread needs to get real specific about the shots he wants taken. I can't make head or tails out of the OP.

No, that's incorrect. If you enlarge the FF image to be identical proportionally to the DX image, the OOF elements will be MORE pronounced!

It would be the same thing as if the FX body was closer to the subject...allowing for a thinner DOF with an identical FOV