The truth about fast glass on m4/3

Started May 21, 2012 | Discussions
topstuff
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The truth about fast glass on m4/3
May 21, 2012

Can someone help me please? I am a bit confused.

I am not trolling, but looking to understand.

If I am shooting with a 24-70 f2.8 lens on , say, a 5D2, what would the equivalent lens be on m4/3?

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

In other words, what is F2.8 in M4/3, when translated into FF or even APSC?

A friend was telling me that their Oly 45mm F.18 was equivalent to a 90mm F1.8 in FF. I am not sure this is right.

Can someone enlighten me with the facts?

Thanks

007peter
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double the focal length and aperture
In reply to topstuff, May 21, 2012

topstuff wrote:

Can someone help me please? I am a bit confused.

If I am shooting with a 24-70 f2.8 lens on , say, a 5D2, what would the equivalent lens be on m4/3?

Awesome wedding photographer combo, none better

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

Generally, you double both the focal length and aperture. So

  • 12mm = 24mm

  • 35mm = 70mm

  • F/2.8 (2 stop) = F/5.6

In term of Bokeh, DOF, a Panasonic 12-35mm f/2.8 is similar to a 24-70mm f/5.6 on full frame Canon 5D.

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Brian Mosley
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In reply to topstuff, May 21, 2012

Interesting thread, thanks for dropping by!

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dotborg
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Re: The truth about fast glass on m4/3
In reply to topstuff, May 21, 2012

To get the same depth of field at the equivalent angle of view, you would need an aperture two stops bigger. With that said, the exposure value would be the same. In other words, if f/2.8 would give you 1/60s on a 135 camera then it will give you 1/60s on a m4/3 camera.

topstuff wrote:

Can someone help me please? I am a bit confused.

I am not trolling, but looking to understand.

If I am shooting with a 24-70 f2.8 lens on , say, a 5D2, what would the equivalent lens be on m4/3?

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

In other words, what is F2.8 in M4/3, when translated into FF or even APSC?

A friend was telling me that their Oly 45mm F.18 was equivalent to a 90mm F1.8 in FF. I am not sure this is right.

Can someone enlighten me with the facts?

Thanks

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jalywol
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Re: The truth about fast glass on m4/3
In reply to topstuff, May 21, 2012

topstuff wrote:

Can someone help me please? I am a bit confused.

I am not trolling, but looking to understand.

If I am shooting with a 24-70 f2.8 lens on , say, a 5D2, what would the equivalent lens be on m4/3?

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

In other words, what is F2.8 in M4/3, when translated into FF or even APSC?

A friend was telling me that their Oly 45mm F.18 was equivalent to a 90mm F1.8 in FF. I am not sure this is right.

There are a LOT of threads about this.

As I understand it, an f 2.8 lens is an f2.8 lens. The differences are not in light gathering, but in DOF between an f2.8 in FF and an f2.8 in M43.

For instance: In terms of light gathering on the M43 sensor, the 45mm f1.8 would have the same results on the M43 sensor as a 90mm f1.8 would have on a FF sensor. The difference between the lenses would be in what you would need to get the same DOF on the M43 sensor as on the FF sensor. In that case, you would need a 45mm f 0.9 lens to equal the FF 90mm f 1.8....but remember this is ONLY about DOF, not actual aperture or light hitting the sensor.

Hope this helps....

-J

Can someone enlighten me with the facts?

Thanks

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Paul De Bra
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Simple calculation, really.
In reply to topstuff, May 21, 2012

If you are shooting at 24mm f/2.8 the size of the aperture is 8.57mm.

If you are shooting at 12mm to capture the same amount of light and achieve the same DOF you need to also have an aperture of 8.57mm which means having f/1.4.

For any m43 lens to be "equivalent" to a full 35mm frame lens it needs to have half the focal length and needs to be 2 stops faster.

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topstuff
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Re: Simple calculation, really.
In reply to Paul De Bra, May 21, 2012

Paul De Bra wrote:

If you are shooting at 24mm f/2.8 the size of the aperture is 8.57mm.

If you are shooting at 12mm to capture the same amount of light and achieve the same DOF you need to also have an aperture of 8.57mm which means having f/1.4.

For any m43 lens to be "equivalent" to a full 35mm frame lens it needs to have half the focal length and needs to be 2 stops faster.

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Ah, got it. So f2.8 in 4/3 really IS f2.8, and it gathers the same amount of light so the exposure would be the same as for FF, but the DOF is essentially the same as f5.6. Yes?

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Albert Ang
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Re: Simple calculation, really.
In reply to topstuff, May 21, 2012

topstuff wrote:

Ah, got it. So f2.8 in 4/3 really IS f2.8, and it gathers the same amount of light so the exposure would be the same as for FF, but the DOF is essentially the same as f5.6. Yes?

yep.

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napilopez
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Re: The truth about fast glass on m4/3
In reply to topstuff, May 21, 2012

Yep, you are right. While the fstop number doesn't change despite the crop sensor, for most practcal conversation(bokeh, dof), this lens is equivalent to an f5.6 on a full frame sensor. I wouldn't start talking about light gathering equivalence because that depends on the sensor and the current state of technology. For example, the OM-D can outperform many old APS-C sensors. Imo this is not a big issue on the telephoto end of things, since it's still easy to get practically reasonable DOF isolation like that. The main weakness for m43 as a lens system is wideangle subject isolation.

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J R R S
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Re: The truth about fast glass on m4/3
In reply to topstuff, May 21, 2012

Yes but F1.8 on m43 will give the same shutter durations in the same conditions as F1.8 on any camera system... DOF will be different.

So in effect you can use the camera in as low light situations as you could with a 5D2.

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MadsR
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In reply to topstuff, May 21, 2012

topstuff wrote:

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

It depends on what you are looking at... If you are looking on light-gathering, as in exposure, an f2.8 lens is the same whatever size medium you put it in front of.

What you are probably referring to though, is DoF, and here you are right, a 35mm f2.8 on m43 is the same as 35mm f2.8 on a 35mm chip, but since it is equivalent to 70mm on an 35mm chip you get much further DoF than you would from an equal FoV on FF... Basically we would need a 12-35 f1.4 to get equally thin DoF. Mostly, for thin DoF you would use primes though, on 35mm as well as on m43, the f2.8 zooms are used for their light gathering prowess, having a zoom for ease of use and still be able to shoot in low(ish) light.

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Daz90
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Re: Simple calculation, really.
In reply to topstuff, May 21, 2012

I always found it simpler to say that a lens at any given focal length is ALWAYS the same light gathering and also the same DOF.

The only difference is the crop/FOV, so if you stitch a 2x2 m4/3s it will for all intents and purpose be the same as a 35mm fullframe sensor.

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papillon_65
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Consider yourself enlightened.
In reply to topstuff, May 21, 2012

topstuff wrote:

Can someone help me please? I am a bit confused.

I am not trolling, but looking to understand.

Judging by your comments under the dpr review I'd have to dispute that.

If I am shooting with a 24-70 f2.8 lens on , say, a 5D2, what would the equivalent lens be on m4/3?

Sure, focal length would be 12-35 ( like the new announcement from Panasonic) but am I right in thinking that the max aperture would have to be , say, F1.8 or thereabouts to have the same effective light gathering as a f2.8 on FF?

In other words, what is F2.8 in M4/3, when translated into FF or even APSC?

A friend was telling me that their Oly 45mm F.18 was equivalent to a 90mm F1.8 in FF. I am not sure this is right.

Can someone enlighten me with the facts?

Thanks

The facts are that it will perform the same as any other zoom of it's type with the exception of dof which you already know. However it is significantly smaller and lighter than its APS and FF equivalents. If you don't use m4/3's I wouldn't worry about it.
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Joe Pineapples
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Oh good - another stupid equivalence thread... (n/t)
In reply to topstuff, May 21, 2012

Joe

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simpy
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intensity vs. total light flux
In reply to topstuff, May 21, 2012

topstuff wrote:

Ah, got it. So f2.8 in 4/3 really IS f2.8, and it gathers the same amount of light so the exposure would be the same as for FF, but the DOF is essentially the same as f5.6. Yes?

Not quite. Both f/2.8 lenses project an image onto the sensor with the same intensity (light flux per unit area). The total amount of light is proportional to the sensor size, so the full frame lens and sensor combination collects photons at a faster rate.

F/5.6 on full frame is the equivalent of f/2.8 in both DoF and total light gathering capacity.

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tommiejeep
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It is all relative...
In reply to topstuff, May 21, 2012

so it is not fast Nikon, Canon glass on FF but is a pretty big leap for m43. My new 14-45 F3.5-5.6 ASPH just arrive (shame my E-M5 was not with it ) do the maths .

If the optics are first class (and is looking that way) and the build quality is top class, big, big leap!
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Knight Palm
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Viral troll epidemic flue ahead
In reply to topstuff, May 21, 2012

topstuff wrote:

The truth about fast glass on m4/3?

It causes lens envy!

Can someone help me please? I am a bit confused.
I am not trolling, but looking to understand.

We're sorry, there's no cure for troll flue, it's more viral than birds flue.

Can someone enlighten me with the facts?

GAS is the only known medicin, however very expensive, but it's safer than lobotomy.

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Banger
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Re: intensity vs. total light flux
In reply to simpy, May 21, 2012

Whilst DOF on u4/3 is 2X FF (a benefit for most unless you want narrow DOF), the exposure at say f1.8 is the same on both cameras.

None of my exposure meters has a setting for FF, 4/3, APSC (or H) etc. The max aperture of any lens is a property of the lens not the camera it's connected to, otherwise every native CANIKON 35mm lens used on APSC needs to have two aperture scales .......they don't do they ??

Which is why when I use my Canon FD lens on my EP-3 (with an adapter), they are still f1.4, f.18, and F2.8 lenses in exposure terms.

Rob

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simpy
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Re: intensity vs. total light flux
In reply to Banger, May 21, 2012

Banger wrote:

Whilst DOF on u4/3 is 2X FF (a benefit for most unless you want narrow DOF), the exposure at say f1.8 is the same on both cameras.

None of my exposure meters has a setting for FF, 4/3, APSC (or H) etc. The max aperture of any lens is a property of the lens not the camera it's connected to, otherwise every native CANIKON 35mm lens used on APSC needs to have two aperture scales .......they don't do they ??

Which is why when I use my Canon FD lens on my EP-3 (with an adapter), they are still f1.4, f.18, and F2.8 lenses in exposure terms.

Certainly, 'exposure' is all about light collection per unit area [measured in units of lux seconds].

The point is that exposure is not the same as the total amount of light that is collected, because the latter depends on sensor size. Whether you use an f/1.4 Canon FD lens on full frame or 4/3, the exposure will be identical - and your light meter agrees. However, on a full frame camera the camera + lens will collect light at a faster rate than on 4/3. In this example, the extra light is collected at the edge of the full frame image (beyond the 4/3 sensor edge).

In another example, if you compare a 25mm f/1.4 lens on 4/3 with a 50mm f/1.4 lens on full frame, the latter also collects more light. In this case the field of view is equal, but the extra light is gathered at higher incidence angles (the object 'sees' a larger aperture), which results in shallower DoF.

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rrr_hhh
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Who cares about the total light flux
In reply to simpy, May 21, 2012

You are just messing things up. Who cares about the total light gathered ( but perhaps the pixel peepers shooting at high ISO) ?

For all practical purposes, what is important is that the light intensity is the same : F2.8 on mft will require the same shutter speed as F2.8 on a FF or an APSC sensor.
DOF however will be multiplied by 2.

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