Read definition of F stop, please. See my links above.
The cropped sensor needs more amplification for the same brightness.
It is not accurate statement. Bigger sensor from same manufacturer with same resolution collects more light, hence more electrons in each sensor well. Here we assume that exactly same ideal lens is mounted made for FF.
If 3/4 of the light of the lens falls outside of the sensor when you crop the sensor, it does not take much to realize that the image can not be as bright any longer with 1/4 of the light. But thankfully the camera engineers are smart and have adjusted the brightness to similar level. The cropped sensor needs more amplification for the same brightness.
If you have a window in a cottage and block 3/4 of the window, will the brightness be the same inside now? Obviously this will not change the brightness outside the hut.
@Vitaliy_Kiselev Sorry, I must have missed it? Thanks for splitting it, though!
Maybe you could make a topic name that makes it more accessible though? As this is a very common misconception. I see people also thinking that a particular mount will make a camera behave differently.. again a different topic but there are so many misconceptions related to this, and many "experts" who do little to make it better, or worse: spread misinformation.
Obviously there are many topics on the matter so if you don´t want to do it - I understand completely.
(on third thought, maybe information on sensor sizes and behavior could be added to the FAQ – end of this topic)
Higher AVERAGE amount? That makes no sense. Higher total, yes - since a larger sensor covers more of the image circle. (the full amount of light that a lens transmits) The last line of your post seems correct, however I object to the conclusion of your first sentence.. (as described above). Obviously, at certain points there might be differences in average light (between different sensor sizes) too (like towards the edge of the image circle there is less light), but these differences would be too small to even take into consideration as a principle in normal circumstances.
In physics terms, the light power at any single point through a lens will be the same at any F stop. However, if you are measuring the total light that hits a sensor, then yes, a larger sensor will have a higher average amount of light upon it. This, of course, has no bearing on actual perceived brightness because the size and efficiency of the pixels now dominate how much brightness is digitized. So the actual light is not brighter, but the overall power is larger on a larger sensor.
Gentlemen, it's pretty common knowledge at this point that an f/2.8 lens is going to be brighter on a full frame than on an MFT sensor/camera.
You are quite mistaken in your "common knowledge".
f2.8 is NOT, I repeat NOT going to be brighter on a full frame than on a any other sensor size. It´s the same. The lens determines how much light that is transmitted to the sensor and a bigger sensor makes no difference in that.
Yep. This is correct. f2.8 will have the DOF of around f4 on a FF sensor... but it's the same amount of light.
f2.8 is NOT, I repeat NOT going to be brighter on a full frame than on a any other sensor size. It´s the same. The lens determines how much light that is transmitted to the sensor and a bigger sensor makes no difference in that. It´s just bigger. DOF is a different story, but that wasn´t the question in this case. (an f2.8 will be less shallow on a smaller sensor than on a bigger one)
IF there is a difference in terms of low light performance (between full frame and smaller) it´s because the bigger sensor (if equal to the smaller in constitution) will produce a bigger image, that in turn can be downscaled - which makes grain e.t.c. less apparent. If sensors are equal, images will be of exactly equal brightness at the same F stop. (on the other hand, you will need to stop down the lens more on a full frame to achieve a long DOF in comparison to a smaller sensor - and that can be a clear disadvantage in low light situations.
P.s. if you don´t believe me, ask yourself this: have you ever seen a light meter where you had to specify sensor / image size?
Sorry, but someone always brings up this whole F-Stop and FF thing. Next time I won't respond.
@DealjagdLtd @Kristo_Ketis @John_Farragut
Please, stop this offtopic.
If you have questions then go to http://www.personal-view.com/faqs/camera-usage/general-camera-usage-faq
If this is not enough, google and read for few extra minutes.
Please do not feed the trolls. And if your lens is brighter, then you should be happy and take photos.
Of course, full frame has less noise and more dynamic range, so you can "boost" an underexposed image and still get the same quality as MFT -- I think. But my technical know how about sensors isn't that big. So maybe technically, you could underexpose FF compared to MFT. But in reality, both cameras with same F-Stop, exposure and ISO would still result in same brightness of picture, I believe.
You are wrong with f. f2.8 cannot be different in any camera. If it is 2.8 it is 2.8. You are thinking in wrong way. You think that if the same lens goes to a FF camera it will be different. NO. It will be the same. With your thoughts the same lens should have the same lightness in all MFT cameras. This has been talked in many forums and the real thing is that most of times has wrong way of talking for this. f has to do with analogue open of the lens, nothing more. If the lens is opened in a specific number of f then it is the same, even if you use a bigger sensor than FF camera. We cannot say this f is different if the lens is used in a different size sensor camera. We can say that the sensor of a camera gives as lighter picture for other reasons. If you have fully opend the lens you cannot open it more if you use it in the FF camera. It has the same number of stops as a lens. Optics are different thing from a camera sensor capabilities.
We use analogue photo cameras for decates now. Digital world make things and information difficult to understand correct and messed the things up.
Sorry for my bad English.
When you have F/2.8 at 35mm-Frame (it's NOT Full-Frame!), and F/2.8 and you exposure both with 1/500 sec. and ISO 200. Then it will be the same Brightness.
@onionbrain We're talking F-stops not T-stops, right?
"Also f/2.8 is the same for MFT as full frame."
No, it's not.
"F2.8 is a lens specification and not a camera specification. Depth of field depends on the lens and the sensor size. Focal ratio only depends of the lens specifications."
All of which has nothing to do with what I wrote.
Gentlemen, it's pretty common knowledge at this point that an f/2.8 lens is going to be brighter on a full frame than on an MFT sensor/camera. This has nothing to do with my original point -- that offered possible reasons why no one had their mind blown with the video quality of those sample videos posted. If you'd prefer to go with the explanation that those videos sucked because the GH3 sucks -- well -- fine.
F2.8 is a lens specification and not a camera specification. Depth of field depends on the lens and the sensor size. Focal ratio only depends on the lens specifications.
@onionbrain You can download the original files via the downloads section. The original -- unaltered -- .mov or or .mp4 container. You have to download it seperately.
Also f/2.8 is the same for MFT as full frame.
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