Lens 'equivalence' between Full Frame - Crop Sensor 1.6 - M4/3

very

very

Member
I'm using the Canon EF 85mm F1.8 on 5D2 (full frame sensor). It's a combination that produces beautiful sharp images that have a very shallow DOF and attractive bokeh.
Focusing is super fine and demands careful placement - for example if used at F1.8 on a face for interviews etc the subjects pupil is in focus while the corner of the eye starts to go!
So, 2.8 for talking heads is just wonderful and dreamy (especially if a 'Black Mist' or similar is used).

All that being said my question is......in terms of basic field of view, magnification and DOF what could give something very similar to the 5D2 FF & EF85 F1.8 combo on a 1.6 crop sensor (say Canon 600d) and a M4/3 sensor (say GH5s).

I tried a Canon EF 50mm F1.4 on the 600d (1.6 crop) and it wasn't as close as I expected - it didn't have nearly the visual compression and shallow DOF I thought it might.
 
You can get a pretty clear idea of what lens you would need to use on an APSC sensor Canon to approximate the DOF you are getting with an 85 mm F/1.8 lens on FF at let's say 10 feet.

FF 85 mm F/1.8 @ 10 feet gives you a total DOF of 0.44 feet

Using an APSC 1.6 Crop sensor, to equate that FF DOF and FOV would require approx a 53 mm F/1.2 lens. An F/1.1 would be a closer match.

An APSC 53 mm F/!.2 @ 10 feet gives you a total DOF of 0.48 feet

So still not as shallow as your FF 85 mm F/1.8 at 10 feet.

These two different lens lengths on the two different size sensors would also give you similar near and far limits of focus.

Try this DOF calculator where you can play with virtually any combination of sensors, lens lengths and apertures.

Chris Young

https://dofmaster.com/mobile/index.html
 
I think it is pretty simple.

You are going to need about a stop of lens speed for a 1.5 crop.

So to s35 look like F2.8 fullframe you will need a F2.

So get the look of F1.4 fullfram you need a F1.0 ... which usually is not available.

You will struggle to match s35 and FF for thin DOF unless you can afford 'masterprimes'
 
very said:
I tried a Canon EF 50mm F1.4 on the 600d (1.6 crop) and it wasn't as close as I expected - it didn't have nearly the visual compression and shallow DOF I thought it might.
Click to expand...

using my ' complex formula' above a S35-1.4-50 and FF-2-80 should match

You must keep the framing the same.
 
Thanks for your replies fellas.
With the kit I have it would seem that the Canon EF 50mm f1.4 would, as tried, give the closest approximation to the FF 85mm 1.8 on the crop sensor APSC.
Next experiment is to try the EF 50mm f1.4 on the GH5s with a Viltrox EF-M2 II 0.71x - it delivers f1.2 from that lens.
Feedback coming.
Regarding the 5D2 - I was using Magic Lantern (Zeeks build) to deliver RAW video at 1880x1058 @126mb/s and 2048x1152 @146mb/s in 3x crop zoom mode.
Stable. however the limitations of the file system on the 5D2 (fFAT?) meant that each shot was split at approx every minute or so (4gb limitation)
It looked very pleasing, capturing a little fading Autumn beauty in late afternoon light nicely - natural colours, good detail and very limited noise without any grading or correction easily from the MLV App. A fine upgrade for an already good - if ageing - camera.
 
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