Potential for background blur

[Impulses]

As someone considering m4/3 I find this really interesting as one of the downsides frequently quoted is subject separation. I'd be keen to see more examples with different lenses...

How much more control you want over DoF can be pretty subjective, but I've never found myself wanting more subject separation out of my M4/3 teles... Wides OTOH are part of the reason why I started shooting FF too, to an extent. Just dividing the FL by the f-stop as the OP alludes to can give you an idea of how the formats compare, a fast FF wide or normal can be in the same ballpark as a short M4/3 tele, etc.

There's a reason lenses at longer FLs start ending up at about the same size regardless of format or imaging circle (eg Oly 75/1.8 vs SY 75/1.8, any 100-400 vs another, etc.). There's also less direct equivalents at those FLs than at wider FLs tho, nobody makes a modern 135/3.5 for FF for instance.

 

[Impulses]

I am not sure what you think is too complicated? All you need to know is the size of the entrance pupil which (as you say) can be got by dividing the focal length by the f-number.

The entrance pupil determines the size of the blur irrespective of the sensor size. Bigger sensors typically use bigger lenses with bigger entrance pupils for the same angle of view.

At longer FLs & AoV, yes, at shorter FLs that's more debatable... There's a lot more overlap at shorter FLs and even plenty of instances where similar size lenses on larger formats have a larger entrance pupil (again, at UWA thru normal FLs) than something that's not any lighter or smaller on a smaller format... Sometimes there's an uptick in weight yet not in size too, there's like 3 or 4 examples of that between my M4/3 & FF kits.

I do think what both of you are presenting is a very useful way of looking at different kits tho, it makes really unique options like the Oly 75/1.8 stand out in fairly obvious ways IMO.

 

[Tom Axford]

I do think what both of you are presenting is a very useful way of looking at different kits tho, it makes really unique options like the Oly 75/1.8 stand out in fairly obvious ways IMO.

I think it very unlikely that any FF camera manufacturer makes a lens that is anywhere near being equivalent to the 75/1.8. Most of the FF lenses I have seen that are around 150mm focal length are twice the price and three times the weight of the MFT lens. Of course, they have much larger entrance pupils, but, on the whole, FF lenses don't give you the choice of very small and light lenses at the longer focal lengths.

 

[Impulses]

I do think what both of you are presenting is a very useful way of looking at different kits tho, it makes really unique options like the Oly 75/1.8 stand out in fairly obvious ways IMO.

I think it very unlikely that any FF camera manufacturer makes a lens that is anywhere near being equivalent to the 75/1.8. Most of the FF lenses I have seen that are around 150mm focal length are twice the price and three times the weight of the MFT lens. Of course, they have much larger entrance pupils, but, on the whole, FF lenses don't give you the choice of very small and light lenses at the longer focal lengths.

Yeah, that was my point there. They used to make slower and smaller 135mm during the film era (some even work reasonably well on current bodies), but almost no one has done a slower one in a good long while. The Batis 135/2.8 is the only one I'm aware of and it's still 2x the weight and price, and if you adjust for the different FL it's really only about a third of a stop faster by equivalence (or 42 vs 48).

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

 

[Tom Axford]

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

Yes, that's why I am totally committed to MFT and have given up FF.

The 35-100/4.0-5.6 is even lighter still (ridiculously small and light when you think of the FF alternatives), yet still gives very good IQ. All that you lose is that larger entrance pupil (and the associated weight and cost). Image stabilisation makes the slower shutter speeds viable, so it's really just a loss of blur capability if you don't need the higher shutter speeds to stop subject movement.

 

[strawbale]

don't forget the excellent Sigma 56/1.4 = 40

and Pana 200/2.8 = 71

 

[Mike Micro 43]

don't forget the excellent Sigma 56/1.4 = 40

and Pana 200/2.8 = 71

I have the Sigma and it does produce lovely results...

However it can be bettered by some adapted cinema lenses I use with Micro 4/3:

A Meopta 100mm F/1.7 with a focal reducer gives 72mm F/1.2 which would be 60, and an ISCO 140mm F/2.1 with reducer giving 100mm F/1.5 so 67:

Mike.


Olympus E-M1 MkII with Meopta 100mm F/1.7 + Focal Reducer (72mm F/1.2)




Olympus E-M1 with ISCO-Gottingen 140mm F/2.1 + Focal Reducer (100mm F/1.5)

 

[Impulses]

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

Yes, that's why I am totally committed to MFT and have given up FF.

The 35-100/4.0-5.6 is even lighter still (ridiculously small and light when you think of the FF alternatives), yet still gives very good IQ. All that you lose is that larger entrance pupil (and the associated weight and cost). Image stabilisation makes the slower shutter speeds viable, so it's really just a loss of blur capability if you don't need the higher shutter speeds to stop subject movement.

Yeah I've kept both the 35-100 in my kit even tho I'm using the f2.8 more... I think it has a bunch of advantages beyond the speed, but it's nice to have an even tinier option with that range that'll still put any phone to shame. I think that totally flips at the other end of the FL range tho (UWA thru normal), and that's why I'm now shooting both formats (M4/3 & FF).

 

[ahaslett]

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

Yes, that's why I am totally committed to MFT and have given up FF.

The 35-100/4.0-5.6 is even lighter still (ridiculously small and light when you think of the FF alternatives), yet still gives very good IQ. All that you lose is that larger entrance pupil (and the associated weight and cost). Image stabilisation makes the slower shutter speeds viable, so it's really just a loss of blur capability if you don't need the higher shutter speeds to stop subject movement.

Yeah I've kept both the 35-100 in my kit even tho I'm using the f2.8 more... I think it has a bunch of advantages beyond the speed, but it's nice to have an even tinier option with that range that'll still put any phone to shame. I think that totally flips at the other end of the FL range tho (UWA thru normal), and that's why I'm now shooting both formats (M4/3 & FF).

My copy has lower resolution than the 12-32 and poor contrast. Could you post some images from yours, so I can compare?

thanks

Andrew

 

[Impulses]

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

Yes, that's why I am totally committed to MFT and have given up FF.

The 35-100/4.0-5.6 is even lighter still (ridiculously small and light when you think of the FF alternatives), yet still gives very good IQ. All that you lose is that larger entrance pupil (and the associated weight and cost). Image stabilisation makes the slower shutter speeds viable, so it's really just a loss of blur capability if you don't need the higher shutter speeds to stop subject movement.

Yeah I've kept both the 35-100 in my kit even tho I'm using the f2.8 more... I think it has a bunch of advantages beyond the speed, but it's nice to have an even tinier option with that range that'll still put any phone to shame. I think that totally flips at the other end of the FL range tho (UWA thru normal), and that's why I'm now shooting both formats (M4/3 & FF).

My copy has lower resolution than the 12-32 and poor contrast. Could you post some images from yours, so I can compare?

thanks

Andrew

Of the 35-100 f4-5.6? I can do that... At what FL? Focused near or far? I did say the 35-100/2.8 has several advantages vs it even beyond the speed, heck I often favor the 42.5/1.7 + 75/1.8 over the 35-100/2.8. I've been meaning to do a comparison between some of these teles and my vintage/manual ones on E mount for my own curiosity.

 

[Impulses]

I meant to get into this in my previous comment but anyway, this is not a shot at or a case for either format, if anything it's a case for both. I think fast and wide is just more challenging on smaller formats...

Here's a bunch of instances for me at UWA thru 50mm equivalent (mostly of stuff I've owned or in one instance almost bought, so not merely cherry picking) where the similarly sized FF lens in my kit actually has an equivalent f-stop / entrance pupil advantage. The weight, feature set, and build advantage goes either way throughout these examples but each pair is very similar in size as I first said:

- Sony 20mm f1.8 G vs CV 10.5mm f0.95: https://bit.ly/3bENiFF


entrance pupil / blur potential / equivalency: same-ish (the Sony is actually a little closer to 19mm)

The Sony is actually lighter, cheaper, better corrected wide open, and has AF. The CV has better sunstars and some other unique rendering characteristics.

- Samyang 45mm f1.8 vs Pana Leica 25mm f1.4 II: https://bit.ly/3bD81Kc


pupil / blur / equiv.: 25 vs 18

The SY is once again lighter and cheaper, both have some rendering advantages tho I think the PL is smoother overall but the SY is relatively sharper wide open, the PL is weather sealed and has linear MF.

- Sony 24mm f2.8 G vs Olympus 12mm f2: https://bit.ly/3bzNoyx


pupil / blur / equiv.: 8.6 vs 6 (subbed in the 28-60 for missing 24/2.8, same size)

The Sony is cheaper, weather sealed, and has a declickable aperture wheel and a nicer hood (Contax GG-2 highly recommend for the Oly). The Oly has somewhat nicer rendering and even nicer feeling build but it's overpriced at retail IMO.

- Sony 35mm f1.4 GM vs Olympus 17mm f1.2: https://bit.ly/3SpyEmi


pupil / blur / equiv.: 25 vs 14

The Sony is heavier and has an aperture wheel, the Oly is excellent tho I just sold it... I think this one is actually the biggest iris opening difference at a similar size amongst these, tho also the biggest weight difference against FF.

I think the differences are just as stark when you start comparing UWA zooms or some of the larger premium zooms for M4/3 (eg 12-40 & 12-100) vs some of the smallest for FF (eg Sigma 28-70 & Tamron 28-200), but the FL, feature set, and the body behind the lens start creating more meaningful differences w/those as well.

At short tele FLs and longer both formats go down very different roads tho... And so that's why I'm shooting both, for the foreseeable future tbh.


pupil / blur / equiv.: 48 vs 42 (don't mind the cropped hood)

Even an APS-C crop out of a similarly sized FF lens doesn't really measure up to the Oly 75mm...


pupil / blur / equiv.: 32 vs 42 (ignore the hood again)

I could go on and throw the 350g internal zooming 35-100/2.8 or 40-150/4 Pro against some (of the lightest) 550g+ external zooming FF teles, but I'll leave it at that, heh. Use case and cropping leeway for a given body blur the lines a little but teles for both formats are still apples and oranges, whereas at shorter FLs there's a ton of overlap IMO.

~75-85mm seems to be the fork in the road...

 

[Jan Steinman]

It is well known that the maximum amount of background blur depends on the size of the entrance pupil of the lens.

That's the first I've heard it put that way.

I've always told my students that it depends on two things: focal ratio (mis-named "aperture") and reproduction ratio. I didn't make that up. It came from two different text books.

The second part of that is not to be underestimated. It's the entire reason that "crop sensor" cameras have a poor reputation for bokeh, which you can solve simply by getting half as far away!

So, I'd say a close focusing lens therefore has more potential for background blur than one that does not focus as close, even if they both have identical "entrance pupils."

 

[Jan Steinman]

You take a theoretical 50mm f4 normal lens on full frame. It will have a entrance pupil of 50mm / 4 which gives 12.5 mm.

Now you to get an "equivalent" micro four thirds normal lens you would need a 25mm f2. It will have an entrance pupil of 25mm / 2 which gives you the same 12.5mm!

Since they have the same entrance pupil size, shouldn't the blur amount be the same? Or am I not understanding something here?

Because the sensor is smaller, the reproduction ratio is smaller, too.

Background blur is affected by both focal ratio and reproduction ratio.

 

[Impulses]

Sure, up to an extent, with certain subjects you wouldn't wanna get much closer or would be taking a very different photo if you're dealing with similar AoV... But subject distance is far too often overlooked in the equation.

 

[ahaslett]

The Oly 75mm mounted on my GX850 is still lighter, and that's why I love it. Heck the 35-100/2.8 mounted on a light M4/3 body is still not much heavier than almost any FF tele zoom by itself (sans body)...

Yes, that's why I am totally committed to MFT and have given up FF.

The 35-100/4.0-5.6 is even lighter still (ridiculously small and light when you think of the FF alternatives), yet still gives very good IQ. All that you lose is that larger entrance pupil (and the associated weight and cost). Image stabilisation makes the slower shutter speeds viable, so it's really just a loss of blur capability if you don't need the higher shutter speeds to stop subject movement.

Yeah I've kept both the 35-100 in my kit even tho I'm using the f2.8 more... I think it has a bunch of advantages beyond the speed, but it's nice to have an even tinier option with that range that'll still put any phone to shame. I think that totally flips at the other end of the FL range tho (UWA thru normal), and that's why I'm now shooting both formats (M4/3 & FF).

My copy has lower resolution than the 12-32 and poor contrast. Could you post some images from yours, so I can compare?

thanks

Andrew

Of the 35-100 f4-5.6? I can do that... At what FL? Focused near or far? I did say the 35-100/2.8 has several advantages vs it even beyond the speed, heck I often favor the 42.5/1.7 + 75/1.8 over the 35-100/2.8. I've been meaning to do a comparison between some of these teles and my vintage/manual ones on E mount for my own curiosity.

At the tele end, focussed over 20ft away, would be good.

Andrew

 

[Tom Axford]

I think it might be helpful to look at the precise mathematical formula for the size of the background (or foreground) blur.

If you have a point of light in the background it will produce a blur whose diameter, b, (measured on the same scale as your subject - whatever the camera is focussed on) is:

b = ax/y,

where a is the entrance pupil diameter; x is the distance from the background to the subject (the subject is what the camera is focussed on); and y is the distance from the background to the entrance pupil.

The same formula works for foreground blur (substitute foreground for background in the definitions of x and y).

You can work out the formula yourself from the geometry:





P is a point in the background. It produces a blur disc QR in the subject plane. When viewed from point T at the top of the entrance pupil, P is seen to be in line with Q. When viewed from point U at the bottom of the entrance pupil, P appears in line with R. When viewed from other points on the entrance pupil it will appear to be in line with points between Q and R.

Hence, when the camera is focussed on the subject plane, P appears as a blur of diameter QR.

A similar argument shows that the foreground point S also is seen as a blur of diameter QR.

The sensor size and focal length of the lens do not affect the size of the blur, but note that the blur is measured on the same scale as the subject. The blur size in the image is mb, where m is the image magnification.

 

[paolop23]

I do think what both of you are presenting is a very useful way of looking at different kits tho, it makes really unique options like the Oly 75/1.8 stand out in fairly obvious ways IMO.

I think it very unlikely that any FF camera manufacturer makes a lens that is anywhere near being equivalent to the 75/1.8. Most of the FF lenses I have seen that are around 150mm focal length are twice the price and three times the weight of the MFT lens. Of course, they have much larger entrance pupils, but, on the whole, FF lenses don't give you the choice of very small and light lenses at the longer focal lengths.

yes the 75f1.8 is pretty unique.

The manual 135mmf3.5 have been mentioned (very cheap like $20 i read) but theres nothing available with AF.

You could crop the 61MP A7R4 with the Samyang AF 75f1.8 though, which is half the price of the Oly, making it a 75-150f1.8-f3.6 zoom lens with 61-12MP output. Not bad thinking about it, since 150mm is actually too long for portraits more often than not...

 

[Impulses]

I do think what both of you are presenting is a very useful way of looking at different kits tho, it makes really unique options like the Oly 75/1.8 stand out in fairly obvious ways IMO.

I think it very unlikely that any FF camera manufacturer makes a lens that is anywhere near being equivalent to the 75/1.8. Most of the FF lenses I have seen that are around 150mm focal length are twice the price and three times the weight of the MFT lens. Of course, they have much larger entrance pupils, but, on the whole, FF lenses don't give you the choice of very small and light lenses at the longer focal lengths.

yes the 75f1.8 is pretty unique.

The manual 135mmf3.5 have been mentioned (very cheap like $20 i read) but theres nothing available with AF.

You could crop the 61MP A7R4 with the Samyang AF 75f1.8 though, which is half the price of the Oly, making it a 75-150f1.8-f3.6 zoom lens with 61-12MP output. Not bad thinking about it, since 150mm is actually too long for portraits more often than not...

I've got both, the Oly 75/1.8 and the SY 75/1.8 (and an A7R IV), and I still see plenty of reasons to reach for both at different times tbh. The output of the cropped SY should be similar in theory, but the Oly is sharper wide open and cropping by 2x while useful does magnify the SY's flaws (I'm not knocking it either, I think it has several advantages over even the larger Sony 85/1.8).

I often stop the SY down a little but I've got no qualms shooting the Oly wide open. If it wasn't for the smallest M4/3 bodies I might not value the Oly as much, heck I might not even have bought it, having it mounted on a second body and/or being able to take it to concerts on a tiny body really raises it's value for me tho.

If it was largely for portraits I'd be tempted to step up to something like the Sigma 85/1.4 DN (2x the weight of the Oly 75 tho), since that then gets you a fast 85mm and a 135/2.2 after a crop... For landscapes I'd probably go with the Sigma 90/2.8 (135/4.1 in cropped mode).

I've stuck with the SY 75/1.8 for my Sony body because I do a little of both and I find the extra shooting distance leeway useful, tho I've been toying with a manual 135mm and I've got a 100mm macro and the Oly 75mm as well. Probably sounds like clutter/redundancy to some but I like the range of options. If there was a small AF 135 for FF or a variable 70-200 closer to 400g (ie closer to my 35-100) I'd have a lot less reason to keep shooting M4/3...

I'm not sure either of those things will become reality anytime soon tho, so two systems it is.

If I'd splurged on something like the PL50-200 I'd probably value that a lot too, the smallest FF 100-400 teles might have a roughly 2/3 EV advantage but they're still 2x the weight of the PL... You could crop a cheap 70-300 that's about the same weight (if looking at the very lightest one w/o OIS) but there's even more issues there than in the SY vs Oly 75 scenario. I'm not sure to what extent these unique / lightweight tele combos are a draw towards M4/3, but OM should lean into it IMO.

It seems they and Pana have thought about longer FLs a lot more than short/mid teles but birders who need the absolute longest teles aren't the only ones that appreciate lightweight ones. The 40-150/4 was encouraging.