[Brightcolours]

It's still a f4 lens in terms of light gathering capability.

Also, f8 at 600mm is plenty thin enough.

Of course it isn't. The size of the hole is the same as with a FF 600mm f8. The cone of light gathered is the same too. So how can it gather more light?

 

Due to the smaller sensor, an f4 lens on MTF gathers less light than on FF 135 format. That is where the noise advantage for FF sensors comes from too.

 

The 'F8' equvialency is only for DOF; and while you can argue it is relevant to total light gathering; it is also very misleading esp when one is concern about shutter speed not light gathering.

No, it is not misleading at all. Nothing is stopping you from using a similar exposure time.

Yes the lens gather less total light because the sensor is smaller but the amount of light that strikes a certain spot is the same

There is no "a certain spot" of any meaning where the light "striking it" is somehow the same.

There are only two meaningful "spots": The whole sensor (the image) and a photo sensitive diode "pixel". Neither will receive the same amount of light.

whether the lens is designed for 6x7 or 4/3.

The lens will give a diffrent FOV too. So, everything basically is different. On 6x7 MF it will give a different FOV, a different DOF, AND a different amount of light is gathered.

So it is a 600F4 lens equivalent with regards to shutter usage (ability to stop motion) and I think that is the relevant point.

No, it is not at all a relevant point. You are shooting with sensors with different sensitivities, yet somehow you place meaning in camera ISO settings giving the same number? Why? One can set the ISO setting to whatever one needs. Set equivaleny ISO settings, obviously. There is no limitation there.

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If you shift the argument to FF can use higher iso with less noise then there will be a long debate on just how much higher can the ISO be with with camera; after all the fuji apsc does quite well compared to the 5d Mk 3; so perhaps we shouldn't go in that direction ?

In which direction are you trying to shift the argument here?

[felix]

Maybe what they are trying to say is: "It's equivalent to a 600mm w.r.t to FOV. DOF is very thin at this point and (most importantly) f/4 is good enough considering the ISO-capabilities of current m43 cameras."

And I think I agree with this Also, there is no 600mm f/8 lens to compare with as far as I know and the usual 600mm f/4 play in a different league (also in terms of price, size and weight) so this equivalence discussion is a bit pointless anyway isn't it?

[thxbb12]

Of course it isn't. The size of the hole is the same as with a FF 600mm f8. The cone of light gathered is the same too. So how can it gather more light?

 

f/4 on MFT meters the same as f/4 on FF. Similarly an f/4 lens on APS-C or medium format would meter the same. The sensor size is irrelevant.

Relative to the sensor size, the amount of light hitting the MFT sensor is the same as a f/4 would be on FF. Consequently, the exposure time is similar.

This is what I meant to say.

 

What really matters is that a 300mm f/4 MFT lens acts as a 600mm f/4 FF equivalent lens in terms of exposure and f/8 in terms of DOF. That makes it for a hand hold-able system which is not the case when considering FF.

[Brightcolours]

f/4 on MFT meters the same as f/4 on FF. Similarly an f/4 lens on APS-C or medium format would meter the same. The sensor size is irrelevant.

Sensor size is NOT irrelevant. What is irrelevant is what you are saying (that "f/4" meters the same").

A lens does not meter. Would you give ISO 100 film and ISO 640 film the same exposure duration? No?

Why is that?

Maybe because they have different sensitivities?

Ok. So, why are you adamant in exposing sensors with different sensitivities the same? Sensors with smaller pixel/sensel/photo sensitive diode pitch have different sensitivities).

 

Point is: ISO is NOT what it used to be with film. One does not set a meter to meter for a certain film sensitivity anymore. Now one simply changes the ISO setting for whatever a certain image requires, and ISO is not about sensor sensitivity.

So don't bring in "metering at f4" as argument, it basically is a non-argument. Set the cameras to equivalent ISO settings and "f4" will NOT give similar exposure results. Nor similar DOF results.

Relative to the sensor size, the amount of light hitting the MFT sensor is the same as a f/4 would be on FF.

You are saying: the light hitting the MFT sensor is LESS than the light hitting the FF sensor. That is because the MFT sensor is so much smaller (4x less light). Also: suppose the sensors have similar amount of pixels/sensels/photo sensitive diodes. Then the MFT sensels collect 4x less light energy, due to their smaller size. So, both on image level, and on pixel level, the MFT sensor will collect less light at f4.

Consequently, the exposure time is similar.

No, exposure is not similar at all. See above. (Less light per image. Less light per pixel. Difference in sensor sensitivity. You just do not realize that because you misunderstand what "ISO" means in the digital age.)

This is what I meant to say.

 

What really matters is that a 300mm f/4 MFT lens acts as a 600mm f/4 FF equivalent lens in terms of exposure

No, it does not. Get that ISO 100 on MFT does NOT mean the same as ISO 100 on FF. The amplification to the signal will NOT be the same. Just like with film, where a bigger grain gives a higher sensitivity, a bigger sensel will collect more light too. So, would you say that ISO 100 film in a 4/3rds size film camera and an ISO 400 film in a FF film camera get equal exposure, with f/4?

I think you will not. Yet that is what you are saying about MFT vs FF sensors. 

 

With film, ISO says something about sensitivity. With digital, it does not. So, stop looking at ISO as a set thing. That is not valid anymore. With digital, ISO is just about getting more or less similar results REGARDLESS of sensitivity, by applying different amounts of amplification and/or sensor voltage for different sensors.

and f/8 in terms of DOF. That makes it for a hand hold-able system which is not the case when considering FF.

That is nonsense.... Why can you handhold 300mm f4 at ISO 400 and not 600mm f8 at ISO 800? Makes no sense.... One REALLY can change ISO settings to whatever one needs. Or even have the camera do it itself with Auto ISO setting.

 

There is no reason what so ever to set different cameras at the same ISO setting number.

[Brightcolours]

Maybe what they are trying to say is: "It's equivalent to a 600mm w.r.t to FOV. DOF is very thin at this point and (most importantly) f/4 is good enough considering the ISO-capabilities of current m43 cameras."

And I think I agree with this Also, there is no 600mm f/8 lens to compare with as far as I know and the usual 600mm f/4 play in a different league (also in terms of price, size and weight) so this equivalence discussion is a bit pointless anyway isn't it?

You are correct in that there are no 600mm f8 lenses. This is one lens where MFT has a size/weight advantage, just because there is no 600mm f8 (let alone with IS).

 

However, lens equivalency is not about proving MFT is somehow bad/worse (it of course is not). It is just about understanding which lenses do what on which format. Nothing else. It probably will be a nice and attractive lens for MFT.

 

To get an equivalent lens on FF, one would have to get a 300mm f4 and add a 2x TC. Or a 400mm f5.6 lens with an 1.4x TC. The new Tamron 150-600mm will probably be a contender on FF, when closed down to f8.

[thxbb12]

Sensor size is NOT irrelevant. What is irrelevant is what you are saying (that "f/4" meters the same").

A lens does not meter. Would you give ISO 100 film and ISO 640 film the same exposure duration? No?

Why is that?

Maybe because they have different sensitivities?

Ok. So, why are you adamant in exposing sensors with different sensitivities the same? Sensors with smaller pixel/sensel/photo sensitive diode pitch have different sensitivities).

 

Point is: ISO is NOT what it used to be with film. One does not set a meter to meter for a certain film sensitivity anymore. Now one simply changes the ISO setting for whatever a certain image requires, and ISO is not about sensor sensitivity.

So don't bring in "metering at f4" as argument, it basically is a non-argument. Set the cameras to equivalent ISO settings and "f4" will NOT give similar exposure results. Nor similar DOF results.

You are saying: the light hitting the MFT sensor is LESS than the light hitting the FF sensor. That is because the MFT sensor is so much smaller (4x less light). Also: suppose the sensors have similar amount of pixels/sensels/photo sensitive diodes. Then the MFT sensels collect 4x less light energy, due to their smaller size. So, both on image level, and on pixel level, the MFT sensor will collect less light at f4.

No, exposure is not similar at all. See above. (Less light per image. Less light per pixel. Difference in sensor sensitivity. You just do not realize that because you misunderstand what "ISO" means in the digital age.)

No, it does not. Get that ISO 100 on MFT does NOT mean the same as ISO 100 on FF. The amplification to the signal will NOT be the same. Just like with film, where a bigger grain gives a higher sensitivity, a bigger sensel will collect more light too. So, would you say that ISO 100 film in a 4/3rds size film camera and an ISO 400 film in a FF film camera get equal exposure, with f/4?

I think you will not. Yet that is what you are saying about MFT vs FF sensors. 

 

With film, ISO says something about sensitivity. With digital, it does not. So, stop looking at ISO as a set thing. That is not valid anymore. With digital, ISO is just about getting more or less similar results REGARDLESS of sensitivity, by applying different amounts of amplification and/or sensor voltage for different sensors.

That is nonsense.... Why can you handhold 300mm f4 at ISO 400 and not 600mm f8 at ISO 800? Makes no sense.... One REALLY can change ISO settings to whatever one needs. Or even have the camera do it itself with Auto ISO setting.

 

There is no reason what so ever to set different cameras at the same ISO setting number.

 

Wooow, relax, no need to be so agitated.

 

All I'm saying is extremely simple:

An f/4 lens on MFT will meter the same as an f/4 lens on FF. That's what I meant when I said "sensor size is irrelevant". Nothing more, nothing less.

I this context, if you set a D800 with a f/4 lens (no matter the focal - that's not the point here) at ISO 400 and 1/200 for instance, you will get the same exposure as with an E-M1 with a f/4 lens at ISO 400 and 1/200.

I don't care whether ISO 400 on FF is roughly 1-2/3 stop better than on MFT. That's not the point. I was just talking about exposure.

I used to own a D800 and I switched to MFT, so I perfectly know the tradeoffs I made by doing so. To me, the IQ difference *in real life* is not significant.

 

Now, regarding the 600mm equivalent lens.  Yes, you can sure use the combos you mentioned. However, the 300mm f/4 Oly lens will probably have much better IQ than any of the solutions you suggest. Also, as you mentioned, there is no 600mm f/8 lens in existence in the FF world (and if it did, it would lead to AF issues anyway).

Bottom line: to reach 600mm on FF, you need to carry something huge and heavy. That's the whole point of my previous replies.

[Brightcolours]

Wooow, relax, no need to be so agitated.

 

All I'm saying is extremely simple:

An f/4 lens on MFT will meter the same as an f/4 lens on FF. That's what I meant when I said "sensor size is irrelevant". Nothing more, nothing less.

I this context, if you set a D800 with a f/4 lens (no matter the focal - that's not the point here) at ISO 400 and 1/200 for instance, you will get the same exposure as with an E-M1 with a f/4 lens at ISO 400 and 1/200.

I don't care whether ISO 400 on FF is roughly 1-2/3 stop better than on MFT. That's not the point. I was just talking about exposure.

I used to own a D800 and I switched to MFT, so I perfectly know the tradeoffs I made by doing so. To me, the IQ difference *in real life* is not significant.

 

Now, regarding the 600mm equivalent lens.  Yes, you can sure use the combos you mentioned. However, the 300mm f/4 Oly lens will probably have much better IQ than any of the solutions you suggest. Also, as you mentioned, there is no 600mm f/8 lens in existence in the FF world (and if it did, it would lead to AF issues anyway).

Bottom line: to reach 600mm on FF, you need to carry something huge and heavy. That's the whole point of my previous replies.

So what you are saying is that ISO 100 film at f4 gets exposed the same as ISO 400 film at f4.

Because according to you, all that matters is how much light falls on a square millimeter.

 

And not sure why you are starting to talk about the quality of the lens again, apparently you do not read what I have said about that. Understanding lens equivalency (in this context) is not about which lens is the sharpest. Or fastest focussing. Or something like that.

[thxbb12]

So what you are saying is that ISO 100 film at f4 gets exposed the same as ISO 400 film at f4.

Because according to you, all that matters is how much light falls on a square millimeter.

 

Ugh.. It's got nothing to do with film.

 

And not sure why you are starting to talk about the quality of the lens again, apparently you do not read what I have said about that. Understanding lens equivalency (in this context) is not about which lens is the sharpest. Or fastest focussing. Or something like that.

 

The whole point was that MFT allows you to have a handholdable (as in "one that a normal person can carry around") 600mm equivalent which is not something possible with FF.

[Brightcolours]

Ugh.. It's got nothing to do with film.

Your same ISO idea has everything to do with film. You talk about exposure in a film way, where ISO is about sensitivity and square millimeters actually have some kind of meaning...

The whole point was that MFT allows you to have a handholdable (as in "one that a normal person can carry around") 600mm equivalent which is not something possible with FF.

It is very well possible, I gave the option of a 300mm f4 with 2x TC. The camera will have a better grip/balance too.  Is the size/weight of the new 300mm f4 Oly published yet?

[stoppingdown]

It is very well possible, I gave the option of a 300mm f4 with 2x TC. The camera will have a better grip/balance too.  Is the size/weight of the new 300mm f4 Oly published yet?

 

I've done it in the past, but in my case (Nikon D100 + AFS 300 f/4) the resulting f/8 max. aperture was barely enough for the AF to work - in other words, no chances of getting BIF. One of the points of thxbb12 is that with f/4 it's reasonable to expect a very good AF speed.

 

As I asked for some days ago   knowing the size and weight of the new lens is fundamental to place this discussion in context.