Kevin Raber's review of The Olympus 40 - 150mm Lens

[Dynszis]

Kevin Raber writes about the Zuiko 40-150mm f2.8 "Comparing this lens in size and weight to a Nikon or Canon 70-200mm lens will wake you up to where the industry is going and what you are missing."

I'm confused, and don't understand what I'm missing here.

To get an FF (full format) equivalent to MFT, you have to multiply both specs by two: not only the focal length, but also the F number. Therefore, a FF equivalent to the Zuiko would have 80-300mm f5.6.

Where the industry is going? Apparently to a place where there is no MFT equivalent to an FF lens with 70-200mm @ f2.8, since that MFT equivalent would have to have 30-100mm @ f1.4. Last time I checked, there isn't any such MFT lens, neither on the market, nor in the pipeline.

What you are missing? Nothing, there are quite a few FF lenses with 70-300mm @ f4.0-5.6 for full format, and they are neither heavier nor more expensive than the Zuiko that gets so lauded.

Can anyone help me out here and tell me what I misunderstand?

[Slobodan Blagojevic]

... Can anyone help me out here and tell me what I misunderstand?

The "misunderstanding" is only partial. It is true that mft 2.8 is equivalent to a full-frame 5.6, but only for depth-of-field purposes. For light-gathering purposes, it is still 2.8, as compared to 4.5-5.6 for 70-300 full-frame zooms. As such, it allows you to shoot using a shutter speed that is twice faster, or ISO that is a quarter of the one you would have to use on a full-frame camera. With lower ISO, you reclaim some (or all) of the noise advantage the full-frame has.

[Dynszis]

It is true that mft 2.8 is equivalent to a full-frame 5.6, but only for depth-of-field purposes. For light-gathering purposes, it is still 2.8, as compared to 4.5-5.6 for 70-300 full-frame zooms.

If I understand correctly, you believe that a 150mm MFT lens @ f2.8 gathers more light than a 300mm FF lens @ f5.6. If I understand correctly, I believe you are wrong.

The F number  is the ratio of the lens's focal length to the diameter of the entrance pupil. Therefore, the diameter of the entrance pupil of a 150mm MFT lens @ f2.8 is exactly the same as that of a 300mm FF lens @ f5.6.

Moreover, the angle of view of a 150mm lens on a MFT camera is exactly the same as that of a 300mm lens on a FF camera.

Can you explain how a 150mm MFT lens @ f2.8 can gather more light than a 300mm FF lens @ f5.6, when angle of view and diameter of the entrance pupil are identical?

[PeterAit]

You are half right. You multiply the focal length by 2, but not the f stop because the f stop is a ratio based on the actual (not the relative) focal length. Thus, the MFT equivalent to, say, a full-frame 100mm f/2.8  is a 50mm f/2.8.

[Dynszis]

the f stop is a ratio based on the actual (not the relative) focal length. Thus, the MFT equivalent to, say, a full-frame 100mm f/2.8  is a 50mm f/2.8.

It seems to me that logic would suggest the opposite conclusion. Since f stop is based on the actual focal length, the pupil of your "MFT equivalent" @ f2.8 has only half the diameter of the full-frame 100mm f/2.8. Therefore, it gathers only 1/4 the light quantity. We also already established that the depth of field is very different.

In which sense do you believe a full-frame 100mm f/2.8  and a MFT 50mm f/2.8 are equivalent?

[Slobodan Blagojevic]

... Can you explain how a 150mm MFT lens @ f2.8 can gather more light than a 300mm FF lens @ f5.6, when angle of view and diameter of the entrance pupil are identical?

Perhaps "light gathering" is not the right term. Whatever the terminology, all I know, as a pragmatic photographer, is that the following is true:

f/2.8 and 1/125 at ISO 100 =

f/5.6 and 1/125 at ISO 400 =

f/5.6 and 1/30 at ISO 100

Therefore, with a full-frame 300/5.6, you'd either have to increase ISO twice or use a twice slower shutter speed.

[spidermike]

If I understand correctly, you believe that a 150mm MFT lens @ f2.8 gathers more light than a 300mm FF lens @ f5.6. If I understand correctly, I believe you are wrong.

The F number  is the ratio of the lens's focal length to the diameter of the entrance pupil. Therefore, the diameter of the entrance pupil of a 150mm MFT lens @ f2.8 is exactly the same as that of a 300mm FF lens @ f5.6.

Moreover, the angle of view of a 150mm lens on a MFT camera is exactly the same as that of a 300mm lens on a FF camera.

Can you explain how a 150mm MFT lens @ f2.8 can gather more light than a 300mm FF lens @ f5.6, when angle of view and diameter of the entrance pupil are identical?

But also don't forget that on a given sensor a longer focal length works by effectively gathering light from the scene and spreading it over a wider area (the sensor is sampling a smaller part of the scene) so the amount of light hitting the sensor gets smaller with increasing focal length.
So if you take a frame-filling shot of the side of a building with a 300mm lens on FF and a 150mm lens on MFT you have two counteracting factors: the FF/300mm has to spread the same amount of light over a larger sensor area (and therefore a much larger image circle) versus the smaller aperture of the MFT/150mm covering a much smaller sensor.

[Telecaster]

I mount a 100mm lens on my Oly E-M1 and a 200mm lens on my Sony A7r, both lenses at f/2.8. Both cameras set at ISO 200, aperture priority, both aimed at the same subject with the same framing. Now I take a photo with each. What are the shutter speeds? (Hint: the same, given some leeway for differences in sensor performance (actual vs. stated sensitivity), lens light transmission efficiency (t-stop vs. f-stop) camera color/tonal profile and metering characteristics.) f/2.8 is always f/2.8…it results in the same amount of light reaching a given portion (say, sq. mm.) of the imaging medium for a given exposure time regardless of focal length.

-Dave-

[Dynszis]

Slobodan, Peter, spidermike, Telecaster, and everyone else: Would you please be so kind as to indicate with which of the following statements you would disagree?

1.) For any photograph we take, we have four parameters to decide about: Focal length, shutter speed, F-number, and ISO settings.

2.) Changing the focal length affects the angle of view.
2.1) The relation between focal length and angle of view depends on the sensor size. 150mm focal length on a MFT yields the same angle of view as 300mm focal length on a FF

3.) Changing the shutter speed affects the amount of motion blur.
3.1) The relation between shutter speed and motion blur is independent of the sensor size, therefore it's the same for MFT and FF respectively.

4.) Changing the F-number affects the amount of background blur (a.k.a. "bokeh")
4.1) The relation between F-number and the amount of background blur depends on the sensor size. f2.8 on a MFT yields the same amount of background blur as f5.6 on a FF.

5.) Changing the ISO settings affects the amount of image noise.
5.1) The relation between ISO settings and the amount of image noise depends on the sensor size. ISO200 on a MFT yields the same the amount of image noise as ISO800 on a FF.

6.) Parameter sets for different cameras (to wit, MFT and FF) are equivalent if and only if they lead to equivalent results, i.e. the same angle of view, the same amount of motion blur, the same amount of background blur, and the same amount of image noise
6.1) A picture taken with an MFT @ 150mm focal length, 1/125 sec shutter speed, f2.8, ISO200 will have less bokeh and more noise than a picture taken with an FF @ 300mm focal length, 1/125 sec, f2.8, ISO200.
6.2) A picture taken with an MFT @ 150mm focal length, 1/125 sec shutter speed, f2.8, ISO200 will have the same angle of view, the same motion blur, the same background blur, and the same image noise as a picture taken with an FF @ 300mm focal length, 1/125 sec, f5.6, ISO800.

Like I said, please indicate which of these statements you believe is false.

[spidermike]

I am gong to be pedantic here:

4.) Changing the F-number affects the amount of background blur (a.k.a. "bokeh")
4.1) The relation between F-number and the amount of background blur depends on the sensor size. f2.8 on a MFT yields the same amount of background blur as f5.6 on a FF.

You have two things to consider: what is in focus and how the lens renders it. At 200mm my 100-400 will have the same DOF as my 70-200 but the way the OOF is rendered means I can at times seem to see more 'shapes' (as opposed to detail) with the 100-400.

5.) Changing the ISO settings affects the amount of image noise.
5.1) The relation between ISO settings and the amount of image noise depends on the sensor size. ISO200 on a MFT yields the same the amount of image noise as ISO800 on a FF.

As far as I am aware noise is not a linear factor because visible 'noise' (the spots you see on the image) are a result of signal to noise ratio in the circuits and in the circuits the noise is fairly constant so it is not that easy to say visible noise at ISO800 is the same as the visible noise at ISO200
Also, so much depends on the technology and manufacturer of the sensor that there is a lot of overlap so in practice it is not easy to say, and given that even from the same manufacturer the technology (combination of sensor, circuitry, D-A conversion, any initial processing to create even a raw file) in a Canon APS-C is different to the technology in a Canon FF. Some recent Nikon cameras use Sony sensors and from what I saw a year or so ago in comparisons they (Nikon) seem to do a better job of using the sensor than Sony do in their cameras.


6

.) Parameter sets for different cameras (to wit, MFT and FF) are equivalent if and only if they lead to equivalent results, i.e. the same angle of view, the same amount of motion blur, the same amount of background blur, and the same amount of image noise
6.1) A picture taken with an MFT @ 150mm focal length, 1/125 sec shutter speed, f2.8, ISO200 will have less bokeh and more noise than a picture taken with an FF @ 300mm focal length, 1/125 sec, f2.8, ISO200.
6.2) A picture taken with an MFT @ 150mm focal length, 1/125 sec shutter speed, f2.8, ISO200 will have the same angle of view, the same motion blur, the same background blur, and the same image noise as a picture taken with an FF @ 300mm focal length, 1/125 sec, f5.6, ISO800.

I would agree except for two things:
your use of the word 'bokeh': this is a quality rather than a measurable property and is a result of lens technology (you can't even say 'same background blur' for the same reason) and add to that different things appeal to different people. It is more correct to say 'same depth of field'.
Noise, as above

[scooby70]

Kevin Raber writes about the Zuiko 40-150mm f2.8 "Comparing this lens in size and weight to a Nikon or Canon 70-200mm lens will wake you up to where the industry is going and what you are missing."

I'm confused, and don't understand what I'm missing here.

....

Can anyone help me out here and tell me what I misunderstand?

Can I ask what camera / cameras you use?

If you own a "FF"/ 35mm system it'll be a relatively simple exercise to get some way along the road to understanding what Kevin Raber is getting at and as a picture tells a thousand words I'd suggest that you go out and buy a cheap Micro Four Thirds camera (you should be able to pick up a Panasonic G1 for well under £100,) a cheap adapter (under £10 on a well known auction site,) and a 24, 28 or 50mm film era lens (£15-50 each depending upon make and model) You can then shoot a series of shots at different apertures with your chosen lens and compare the results to FF shots of 50/56 or 100mm at equivalent apertures.

IMVHO it's an exercise that is worth doing, I've done it myself and I agree to an extent with what Kevin says in that these days with a CSC you can get... pretty much... the same look you'd get from a FF camera but with kit which is smaller and lighter. The only areas in which a MFT CSC can't match a 35mm/FF camera are (IMVHO, and yes there may be other areas too...) for very shallow DoF (but once you start stopping FF down MTF may be able to match the DoF) and the very highest ISO settings.

Give it a go.

[Slobodan Blagojevic]

This is getting out of hand. You do not need whole pages to say what can be said in a single sentence: the lens in question allows you to use a twice faster shutter speed or twice lower ISO. The shutter speed advantage is unquestionable, the ISO one debatable (i.e., it could result in better noise, or, as a minimum, the same).

[bjanes]

The "misunderstanding" is only partial. It is true that mft 2.8 is equivalent to a full-frame 5.6, but only for depth-of-field purposes. For light-gathering purposes, it is still 2.8, as compared to 4.5-5.6 for 70-300 full-frame zooms. As such, it allows you to shoot using a shutter speed that is twice faster, or ISO that is a quarter of the one you would have to use on a full-frame camera. With lower ISO, you reclaim some (or all) of the noise advantage the full-frame has.

It is not that simple. The full frame f/2.8 has a larger clear aperture and collects more light than a f/2.8 MFT lens. Roger Clark explains the concept of etendue in his post "When f/ratio Does not Tell the Whole Story". Astronomical telescopes are rated in terms of clear aperture, not f/ratio. How this applies to terrestrial photography is not that simple, but the article is worth reading.

Regards,

Bill

[scooby70]

It is not that simple. The full frame f/2.8 has a larger clear aperture and collects more light than a f/2.8 MFT lens. Roger Clark explains the concept of etendue in his post "When f/ratio Does not Tell the Whole Story". Astronomical telescopes are rated in terms of clear aperture, not f/ratio. How this applies to terrestrial photography is not that simple, but the article is worth reading.

Regards,

Bill

I'm not going to attempt to argue with what the guy says as he's no doubt right but what I can say is that it all has about as much relevance to my photography as the colour of my socks.

Back on my planet... oh hang on, another poster was right when he said this is all getting out of hand...

[Telecaster]

Slobodan, Peter, spidermike, Telecaster, and everyone else: Would you please be so kind as to indicate with which of the following statements you would disagree?

No.

-Dave-

[Slobodan Blagojevic]

It is not that simple. The full frame f/2.8 has a larger clear aperture and collects more light than a f/2.8 MFT lens. Roger Clark explains the concept of etendue in his post "When f/ratio Does not Tell the Whole Story". Astronomical telescopes are rated in terms of clear aperture, not f/ratio. How this applies to terrestrial photography is not that simple, but the article is worth reading.

Bill, does any of that change this simple statement: 2.8 lens allows you to use a twice faster shutter speed or twice lower ISO?

[Michael N. Meyer]

Conversations like this make my head hurt. And, for all that headache, they won't make my pictures any better (or anyone else's).

[Ray]

Bill, does any of that change this simple statement: 2.8 lens allows you to use a twice faster shutter speed or twice lower ISO?

That's not quite correct, Slobodan. It allows you to use either a twice fast shutter speed or a twice lower ISO. Using both together would result in a serious underexposure. 

However, if one is comparing an MFT Zuiko 40-150/F2.8 lens with a FF 70-200/F2.8, there's no doubt that the 70-200/F2.8 is more useful in some respects, and the MFT lens more useful in other respects, particularly in its characteristic of providing more DoF at a given F/stop. One source of confusion in such comparisons results from the tradition of always using the full-frame standard to describe lens focal length. The smaller format always has the DoF advantage, and the larger format always the 'shallowness of DoF' advantage at a given f/stop and equivalent focal length. Whether one or the other is considered an advantage or a disadvantage depends on one's style of shooting, and/or the requirements for a particular shot.

In full-frame terms the Zuiko 40-150 becomes effectively an 80-300/f2.8 (excluding DoF consideration) so one might think the Zuiko lens has the advantage of more reach. But that's illusory.

One advantage of the larger, full-frame format is that one always has the option of cropping the image to a smaller format. One doesn't have the option of increasing the 4/3rds format to a larger size. If one takes these options into consideration, the FF 70-200/F2.8, in 4/3rds format terms plus full-frame terms, becomes a 70-400/F2.8. The difference between 70mm and 80mm is not that great, but the difference between 400mm and 300mm is quite substantial.

Also, if one wants to achieve the same shallowness of DoF with the full-frame lens, using the same aperture as used with the Zuiko lens, one can sometimes do so by choosing the appropriate focal length then cropping the full frame image to 4/3rds format, but this approach would not work at the wider focal lengths.

Sorry if such reasoning causes some people's heads to hurt. It's all clear in my mind. 

[bjanes]

I'm not going to attempt to argue with what the guy says as he's no doubt right but what I can say is that it all has about as much relevance to my photography as the colour of my socks.

Back on my planet... oh hang on, another poster was right when he said this is all getting out of hand...

Scooby,

Etendue as discussed in Roger's article has more significance with respect to your photography than you realize. Assume you are shooting in a low light situation with a full frame camera (24 x 36 mm sensor) at f/2.8 and 1/100 sec is necessary to freeze the action and are using an ISO of 1600. If you are using an APS sensor as in the Fuji X-T1 (23.6*15.6 mm sensor) with the same exposure parameters, the light density (photons per square mm of the sensor) will be the same and the histograms should be the same. However, the full frame sensor has 2.35 times the sensor area and will collect 2.35 times the number of photons as compared to the APS sensor and will have a better signal to noise ratio. The SNR is proportional to the square root of the number of photons collected, so the full frame sensor will have a better SNR by a factor of 1.53.

If you increase exposure with the APS camera to collect the same number of photons, you would need to use a shutter speed of 1/43 sec and the image could well be blurred. Would this affect your photograpy?

Regards,

Bill

[Slobodan Blagojevic]

... Assume you are shooting in a low light situation with a full frame camera... at f/2.8 and 1/100... and are using an ISO of 1600. If you are using an APS sensor...with the same exposure parameters, the light density ... will be the same and the histograms should be the same. However, the full frame sensor ... will have a better signal to noise ratio...

Of course. But who is claiming otherwise? It is widely accepted that a larger format will have better noise in general. But that is not the issue the OP has raised. Your example is using the same parameters, we are discussing the OP premise of a m4/3 lens at 2.8 vs. full-frame lens at 5.6. In which case, the noise advantage of the larger sensor could be greatly reduced or even eliminated.