Time to trade her in for a younger model?

[Phra Ek]

Doesn't the 45mm F1.8 do the job for portraits?

Yes - in combination with the 20mm f1.7 - as you need to stand a long way back with the 45mm for whole body shots.

But I'm planning to upgrade my old micro 4/3 body to either a newer model (OMD em-5 Mk2) or to a larger sensor mirrorless (A7 Mk II). Either the new generation Micro 4/3 or the new larger sensor mirrorless will be a big step up in IQ for me .... but I'm still trying to decide which format to go for.

I would like a high quality zoom rather than having to swap between the 20mm/45mm - but I'm not sure if the f2.8 Pro Olympus lens will give the tight depth of field needed when combined with the micro 4/3 sensor? Or if the f3.5 kit zoom will do the job when combined with the larger sensor in the A7.

I'll need to play with both combinations in a shop - but from looking at shots the flickr Groups for the relevant cameras it looks like with a normal 'portrait' lens focal length of between 50mm to 90mm then f2.8-f3.5 gives a tight enough depth of field for portrait work with a larger sensor A7 (depending on how far away the background is), whereas f1.8 is needed for the smaller sensor micro 4/3 body. (And currently there's no f1.8 zoom that I know of)

Now that the IQ and dynamic range of sensors in micro 4/3 and bigger are so close - the critical factor for me is the impact of sensor size on depth of field rather than any quality considerations.

[MJP]

Sony A7r with FE 70-200/f4 G OSS . . .

https://www.flickr.com/photos/56053365@N07/16591541669/in/photostream/lightbox/

[vaultdweller0013]

Doesn't the 45mm F1.8 do the job for portraits?

Yes - in combination with the 20mm f1.7 - as you need to stand a long way back with the 45mm for whole body shots.

But I'm planning to upgrade my old micro 4/3 body to either a newer model (OMD em-5 Mk2) or to a larger sensor mirrorless (A7 Mk II). Either the new generation Micro 4/3 or the new larger sensor mirrorless will be a big step up in IQ for me .... but I'm still trying to decide which format to go for.

I would like a high quality zoom rather than having to swap between the 20mm/45mm - but I'm not sure if the f2.8 Pro Olympus lens will give the tight depth of field needed when combined with the micro 4/3 sensor? Or if the f3.5 kit zoom will do the job when combined with the larger sensor in the A7.

I'll need to play with both combinations in a shop - but from looking at shots the flickr Groups for the relevant cameras it looks like with a normal 'portrait' lens focal length of between 50mm to 90mm then f2.8-f3.5 gives a tight enough depth of field for portrait work with a larger sensor A7 (depending on how far away the background is), whereas f1.8 is needed for the smaller sensor micro 4/3 body. (And currently there's no f1.8 zoom that I know of)

Now that the IQ and dynamic range of sensors in micro 4/3 and bigger are so close - the critical factor for me is the impact of sensor size on depth of field rather than any quality considerations.

For depth of field, multiply the f-number by the crop factor to get the equivalent DOF.

A 20mm f1.7 M43 would be the same DOF and (diagonal) Angle of view of a 40mm f3.5 full frame. (This is why understanding the concept of equivalence is important, despite those who dismiss it; it doesn't say that camera X is better than Y or sensor size A is better than B, but it does let you make meaningful comparisons between the results from different sensor sizes, once you define the type of photo you want to take, in this case, what DOF to expect when moving from one size to another).

So, take whatever f-number you are happy with for M43 and multiply that and the focal length by two, and that is what you need for a FF lens to get the same DOF.

[fimgirl]

^^ I'm not arguing the above but my understanding is that when applying the 2x factor it should read as +1 stop on the aperture I.e. f1.4 on a 2x crop sensor will equate to f2 on a full frame.

See here:-

http://admiringlight.com/blog/full-frame-equivalence-and-why-it-doesnt-matter/

If this is the case then it seems that f3.5 FX is equivalent to c.f2.4 cropped and therefore will produce a narrower DOF.

Maybe?

Either way, not much in it.

Edited March 17, 2015 by fimgirl

[fimgirl]

Take a look here:-

http://www.dofmaster.com/dofjs.html

App also available

[vaultdweller0013]

^^ You multiply aperture by the crop factor as well -- try it out on the calculator you linked.

[fimgirl]

All very confusing but I see what you say.

[Phra Ek]

Great info - thank you Vaultdweller and Fimgirl!

If I've understood correctly - then my subjective view that a kit zoom on a full frame camera provides a similar depth of field to an f1.8 prime on a micro 4/3 seems right ...

For portrait work I find using f2.8 on the 45mm Olympus micro 4/3 prime lens gets me the depth of field I need - give or take a stop depending on distances.

Using the calculator that means a 0.8ft DOF. That sounds right for eyes and face in focus and the rest out of focus.

To get the same DOF with full frame using a 90mm lens would be f5.6. This is well within the capability of a decent zoom lens.

So one advantage of a full frame sensor is that I can use a versatile zoom lens for portrait work. I think!

But of course what I also realize now is that Olympus f2.8 Pro zoom lens will also give me the DOF needed as it's a constant aperture f2.8.

So I still can't decide between the Sony A7 II and the Olympus OMD with the Pro lens!

But ...... If I go for the OMD - then I can still use my trusty old Lumix G as a spare body.

[MJP]

I reckon the A7II with Samyang 14mm f/2.8, Samyang 35mm f/1.4, Samyang 85mm f/1.4 and the new Samyang 135mm f/2 is worth a look.

Love Samyang glass. Sharp, great colour and cheap.