Larger sensor just a luxury?

[Dao]

EW, I'm fully aware of the magnification. DoF changed when the final image is magnified. Same as viewing distance. But I am asking you on post #160.

You said it depends on entrance pupils. In the examples they are the same since the focal length and f number are the same. Can you explain a little more on that?

 

[Nikon_Josh]

I don't know what to say, you guys got the information through but I don't agree with it because you guys are just saying that you're right without supporting it. For me, I couldn't get my information/opinion/idea through anyone except Helen B.

Sorry to say this EW, but alot of your views are rather strange and not very well researched at all. You seem to come on more often than not and just come out with stuff that is fiction rather than fact.

You were even shown the other day to have deliberately started a thread to cause a war between Nikon and Canon users which in my opinion is a shameful act on your part and shows the way you conduct your business on this forum.

Yeah, that's my mistake. :/

Ah well, we all make mistakes sometimes!

Just take a step back sometimes, before you jump in...

 

[Helen B]

EW doesn't help himself by being so vague. I've made a couple of attempts to clear his vagueness up for him, but he just goes and rewrites the vagueness back in and loses the ground he's gained. He is, in essence, theoretically correct although there are practical limitations on keeping the entrance pupil the same size and in going to very wide apertures with digital sensors. His point about entrance pupil size, if only he could write it more clearly, is obvious to people who use a wide range of formats.

This thread is now going round in tiresome, pointless circles. All I can suggest is that people attempt to see what he is trying to say, and forgive him for his poor communication. I think that posts #121 and #159 represent what he is trying to say, by the way.

 

[Nikon_Josh]

EW doesn't help himself by being so vague. I've made a couple of attempts to clear his vagueness up for him, but he just goes and rewrites the vagueness back in and loses the ground he's gained. He is, in essence, theoretically correct although there are practical limitations on keeping the entrance pupil the same size and in going to very wide apertures with digital sensors. His point about entrance pupil size, if only he could write it more clearly, is obvious to people who use a wide range of formats.

This thread is now going round in tiresome, pointless circles. All I can suggest is that people attempt to see what he is trying to say, and forgive him for his poor communication. I think that posts #121 and #159 represent what he is trying to say, by the way.

By that same token, he can quite clearly speak much better english than I can speak Malaysian!! So I am not going to be knocking him for that. :thumbup:

 

[mjhoward]

EW doesn't help himself by being so vague. I've made a couple of attempts to clear his vagueness up for him, but he just goes and rewrites the vagueness back in and loses the ground he's gained.

Helen, can you decode this one?

Given that both of the lens are the same size, both will get. Since APS-C sensors' pixel are denser, the light that falls on it is also denser, given that the lens are the same size as full frame. Light in the lens in full frame is spread out more so photons will be more spread out and less dense. Not sure if I'm right too.

I cannot understand how light will become more or less dense based on the sensor it is hitting, all other things being equal of course.

 

[Kolia]

quantum sensors ?

Seriously tho, that post is what made me think EW assumes that the croped sensors still receive the total light even when using an FX lens or that the DX lens is otherwise "concentrating" (I don't want to say focus as I feel it would just confuse him more) the total light in a smaller circle.

 

[Dao]

quantum sensors ? Seriously tho, that post is what made me think EW assumes that the croped sensors still receive the total light even when using an FX lens or that the DX lens is otherwise "concentrating" (I don't want to say focus as I feel it would just confuse him more) the total light in a smaller circle.

That is what I believe as well when he used the magnifying glass example.

 

[EchoingWhisper]

My point is
-same magnification
-same entrance pupil
=
-same radiant flux
-same depth of field

You keep leaving out important variables.

Depth of field is dependent on magnification, focal plane-to-subject distance, and aperture (iris). You cannot say that at the same magnification and same aperture size, the DoF is the same because you're not considering subject distance. If you have a full frame sensor and a crop sensor, then subject distance MUST change in order to keep the magnification constant. And if subject distance changes, DoF must change as well, given everything else stays the same.

Uhm, as I said, given the same magnification, same final image viewing size, same f stop, a larger format would get the advantage in lesser depth of field. But the same f stop on a larger format means a larger entrance pupil. If both format has the same final image viewing size, same magnification, and same entrance pupil diameter, then depth of field shall be the same.

 

[mjhoward]

If both format has the same final image viewing size, same magnification, and same entrance pupil diameter, then depth of field shall be the same.

So if I put an 85 1.4 on a D7000 and snapped a photo of a face that filled half the frame and then put that same 85 1.4 on a D700 and recomposed so that the same face filled the same half frame... you're saying the DOF would be the same? After all, since I'm using the same lens at the same f-stop, the entrance pupil here is no different, along with all other characteristics aside from sensor size.

 

[EchoingWhisper]

If both format has the same final image viewing size, same magnification, and same entrance pupil diameter, then depth of field shall be the same.

So if I put an 85 1.4 on a D7000 and snapped a photo of a face that filled half the frame and then put that same 85 1.4 on a D700 and recomposed so that the same face filled the same half frame... you're saying the DOF would be the same? After all, since I'm using the same lens at the same f-stop, the entrance pupil here is no different, along with all other characteristics aside from sensor size.

True enough, but its not a DX lens anyway. A DX lens with the same entrance pupil as the FX lens would produce the same depth of field at the same magnification.

 

[2WheelPhoto]

If both format has the same final image viewing size, same magnification, and same entrance pupil diameter, then depth of field shall be the same.

So if I put an 85 1.4 on a D7000 and snapped a photo of a face that filled half the frame and then put that same 85 1.4 on a D700 and recomposed so that the same face filled the same half frame... you're saying the DOF would be the same? After all, since I'm using the same lens at the same f-stop, the entrance pupil here is no different, along with all other characteristics aside from sensor size.

True enough, but its not a DX lens anyway. A DX lens with the same entrance pupil as the FX lens would produce the same depth of field at the same magnification.

hmmmm

free bump cuz thats all this thrwad is about. I almost got sucked into this debate heh edit off

 

[Dao]

But the same f stop on a larger format means a larger entrance pupil.

Can someone explain this please?


I always thought f number, or f stop if you will, is focal length divided by the diameter of the entrance pupil. Why is it affected by the recording medium format?

Focal length, the distance when a optics brought the distance subject to it focus. So 50mm on full frame is the same as 50mm on cropped body. It should be independent from the recording medium format. Because it is the physical property of the optics.

So, f number = focal length / diameter

if we keep f number and focal length constant, diameter should be constant.

 

[EchoingWhisper]

Can someone explain this please?

I always thought f number, or f stop if you will, is focal length divided by the diameter of the entrance pupil. Why is it affected by the recording medium format?

Focal length, the distance when a optics brought the distance subject to it focus. So 50mm on full frame is the same as 50mm on cropped body. It should be independent from the recording medium format. Because it is the physical property of the optics.

So, f number = focal length / diameter

if we keep f number and focal length constant, diameter should be constant.

That's right but that would mean a different framing. But if the same equivalent focal length is used, then it'll be another case.

 

[Helen B]

I'll have another attempt at summarising what EW is trying to compare. This time I'll expand on the basic conditions with the direct consequences of those conditions. These parameters are collected by reading through the thread, and they are fairly consistent, though often vaguely stated.

He's doing a 'same picture' comparison with two cameras that have different formats but the same number of sensels (same megapixels) and the same 'size' of lens.

'Same picture' in this case means:
Same subject;
Same subject distance;
Same field of view (therefore different focal lengths for the two different formats); and
Same final image size.

Same lens size has been clarified to mean same entrance pupil size. This implies:
Same luminous flux (and same radiant flux, because the two will be proportional in this case); and
Different f-numbers (a simple and obvious consequence of holding the entrance pupil the same while varying the focal length).

The consequence of having the same number of sensels and the same entrance pupil diameter is that each sensel receives the same 'amount' of light (the same luminous flux). (Of course this assumes a constant sensel area efficiency between the two formats - ie the same proportion of incident light is captured by the sensels of each format.)

The consequence of having the same entrance pupil size but different focal lengths is that the DoF is the same - so it is the 'same picture', as intended in this comparison.

End of description of conditions. ******************

While it is true that the smaller the format the easier it is to make high quality, very fast lenses there are practical and theoretical limits to this for lenses in air. There's the theoretical limit set by optics and thermodynamics: f/0.5. There's the observation that there are very few photographic lenses for any format that are faster than f/0.9. There may be a potential problem with the angles of incidence on a sensor with very fast lenses. It's a good idea, therefore, to separate the understanding of the theoretical parts of this discussion from the practical limitations, while knowing that these limitations exist.

*************************

Helen, can you decode this one?

Given that both of the lens are the same size, both will get. Since APS-C sensors' pixel are denser, the light that falls on it is also denser, given that the lens are the same size as full frame. Light in the lens in full frame is spread out more so photons will be more spread out and less dense. Not sure if I'm right too.

I cannot understand how light will become more or less dense based on the sensor it is hitting, all other things being equal of course.

Here's my translation, given the comparison parameters stated above:

Given that both of the lenses [have the same entrance pupil diameter] both will get [the same luminous flux]. Since [An] APS-C sensor's pixels are denser [than those of a larger sensor with the same number of sensels], and the light that falls on it is also denser [has greater luminance] given that the lens has the same [entrance pupil diameter] as the full frame lens [of the focal length that gives the same field of view because we are taking the 'same picture'.] [The same luminous flux] Light in [from] the full-frame lens is spread out more so photons will be more spread out and less dense.

Is that any clearer?

 

[EchoingWhisper]

I'll have another attempt at summarising what EW is trying to compare. This time I'll expand on the basic conditions with the direct consequences of those conditions. These parameters are collected by reading through the thread, and they are fairly consistent, though often vaguely stated.

He's doing a 'same picture' comparison with two cameras that have different formats but the same number of sensels (same megapixels) and the same 'size' of lens.

'Same picture' in this case means:
Same subject;
Same subject distance;
Same field of view (therefore different focal lengths for the two different formats); and
Same final image size.

Same lens size has been clarified to mean same entrance pupil size. This implies:
Same luminous flux (and same radiant flux, because the two will be proportional in this case); and
Different f-numbers (a simple and obvious consequence of holding the entrance pupil the same while varying the focal length).

The consequence of having the same number of sensels and the same entrance pupil diameter is that each sensel receives the same 'amount' of light (the same luminous flux). (Of course this assumes a constant sensel area efficiency between the two formats - ie the same proportion of incident light is captured by the sensels of each format.)

The consequence of having the same entrance pupil size but different focal lengths is that the DoF is the same - so it is the 'same picture', as intended in this comparison.

End of description of conditions. ******************

While it is true that the smaller the format the easier it is to make high quality, very fast lenses there are practical and theoretical limits to this for lenses in air. There's the theoretical limit set by optics and thermodynamics: f/0.5. There's the observation that there are very few photographic lenses for any format that are faster than f/0.9. There may be a potential problem with the angles of incidence on a sensor with very fast lenses. It's a good idea, therefore, to separate the understanding of the theoretical parts of this discussion from the practical limitations, while knowing that these limitations exist.

*************************

Helen, can you decode this one?

Given that both of the lens are the same size, both will get. Since APS-C sensors' pixel are denser, the light that falls on it is also denser, given that the lens are the same size as full frame. Light in the lens in full frame is spread out more so photons will be more spread out and less dense. Not sure if I'm right too.

I cannot understand how light will become more or less dense based on the sensor it is hitting, all other things being equal of course.

Here's my translation, given the comparison parameters stated above:

Given that both of the lenses [have the same entrance pupil diameter] both will get [the same luminous flux]. Since [An] APS-C sensor's pixels are denser [than those of a larger sensor with the same number of sensels], and the light that falls on it is also denser [has greater luminance] given that the lens has the same [entrance pupil diameter] as the full frame lens [of the focal length that gives the same field of view because we are taking the 'same picture'.] [The same luminous flux] Light in [from] the full-frame lens is spread out more so photons will be more spread out and less dense.

Is that any clearer?

Thank you, you do a much better explaining this and know about this much better.