Beacon Camera Club

I was curious about a remark made in one of the second-hand photography magazines that Members generously make available on Club nights.

The photographer was taking studio portraits with a Nikon D750 set at 1/200 at f/8 for the whole shoot (focal length not specified), and he said:

"The full-frame D750 is great for depth-of-field effects in portraits. It's the closest I can get to medium-format from an SLR."

Now I realise that switching a given lens from a full-frame camera to a medium format one will change the effective focal length and depth of field, just as it would if switching from an APS-C camera to full-frame. However, the photographer here seems to be implying that the camera itself is somehow influencing the 'depth-of-field effects' quite separately from the lens. How might this be?

I think Ruaridh, though without knowing the context, you may have correctly smelt a rat. All cameras are merely light collecting devices, though lenses may behave differently on those devices.
The setting of f8 the writer has stated would likely give a very wide depth of field – not the typical medium format effect with narrower DOF with beautiful out of focus bokeh.

For the benefit of other readers to your post, lenses apparently change their properties depending on the sensor size:
• a MFT 50mm lens at f4 behaves like a FX 100mm lens at f8 (9’4-10’9ft)
• a DX 50mm lens at f4 behaves like a FX 75mm lens at f5.6 (9’1 to 11’1ft)
• a FX 50mm lens at f4 behaves like a medium format 75mm lens at f1.4 (8’8-11’8ft)
also assuming the lenses’ projection covers the whole of their sensors.
Fields of view thus change:
• A MFT 50mm lens behaves like a FX 100mm lens (20 degrees)
• A DX 50mm lens behaves like a FX 75mm lens (27 degrees)
• A FX 50mm lens behaves like a medium format 75mm lens (40 degrees)

Thus you have to change lenses between formats to reach optical equivalency. Thus it is not the camera that gets closer to medium format, but the adaption of the lenses attached to it.

Thanks Phil, and for the additional detail.

I wasn't familiar with the Nikon designations, and initially thought MFT probably stood for Medium Format - but after a bit of Googling I see it is Micro Four-Thirds, so a bit different! A Wikipedia article on DX Format (= APS-C) was also quite helpful - even showing that APS-C is more than one thing! ... and FX refers to Full Frame cameras.

I'm guessing that the distances you've quoted give the range of acceptable sharpness when focused at 10 ft.

Hi Ruaridh - rather than try to precis it, can I point you to this article which makes a good fist of the explanation with practical examples ...? https://fstoppers.com/education/underst ... eld-312599

Thanks Ian. Very clearly explained and puts me right on a couple of points.

It also makes clear, indirectly, that the DoF is going to be the same across all full-frame cameras for a given lens on given settings. (The only other thing I can think of is that when the original author spoke of 'depth-of-field effects' he meant some in-camera processing.)