Opinions on Extenders, please?

[PajamaGuy]

Extender EF 2x III - or the EF 1.4x III.  Same price.  Other than the obvious, why one over the other?  Are the optics equal?

Thanks!

[ebiggs1]

"If you couldn't understand the simple concept that a whole piece of paper is hit by more light than half a sheet of paper then it is useless to discuss this further."

I am sorry I disappointed you.  But the piece of paper got and has the same exposure. Right?  The rest of the light is nothing.

BTW, I already said further discussion was futile. Neither of us is going to be swayed and that's OK.  We just don't happen to agree on this subject.  Perhaps someone better versed than I will do a better job.

[TTMartin]

---

@ebiggs1 wrote:

"If you couldn't understand the simple concept that a whole piece of paper is hit by more light than half a sheet of paper then it is useless to discuss this further."

I am sorry I disappointed you.  But the piece of paper got and has the same exposure. Right?  The rest of the light is nothing.

BTW, I already said further discussion was futile. Neither of us is going to be swayed and that's OK.  We just don't happen to agree on this subject.  Perhaps someone better versed than I will do a better job.

---

Yes, they got the same exposure. The same amount of light PER UNIT AREA. The whole piece of paper has more UNITS OF AREA, than the half sheet of paper so the whole sheet of paper received more TOTAL LIGHT.

[ebiggs1]

"Yes, they got the same exposure."

See we agree!  You are beginning to see "the light". Until we get into electronics, this is all that matters.  Total light is meaningless.  As is all the light that falls out side of the piece of paper.

[TTMartin]

---

@ebiggs1 wrote:

Total light is meaningless.  As is all the light that falls out side of the piece of paper.

---

Total light is not meaningless, because it is the total light that the camera has to process to make a complete picture. 

The light that falls outside of the paper or sensor is meaningless, but, the light that falls on the sensor isn't meaningless. The sensor with more surface area receives the same exposure or same amount of light PER UNIT AREA, but, has more UNITS OF AREA so it receives more TOTAL LIGHT. So the camera has more signal due to the fact that the sensor got more TOTAL LIGHT for any given exposure. And more signal results in less amplification, and less noise.

[ebiggs1]

Mr Martin did you fail to read this long explanation?  I believe we are actually saying the same thing. Or at least in the same ballpark.  Here it is again if you just glossed over it.

I guess we have switch to “noise” now?

Crop factor can only impact the aperture in the sense of DOF, not the exposure. 

One big problem is the very term Crop Sensor.  Crop factor as a concept, or term, exists only to allow photographers to get similar results with lenses used on different size sensors.  It is such a misleading term.  I wish it had never been created.  We never had it in the film days and we had several different formats of film size.  People knew if you used a 50mm lens on a 35mm film camera it gave a certain AOV.  If you use it on a Medium Format the AOV was different.  They didn't need to say, oh let's see it is 1.6x or no a 1.5x or ..........

So here we are.  Why does the full frame camera (seem to) have a cleaner signal? The photosites on the full frame sensor can be twice as large as the ones on a crop sensor. Photosites on a sensor are like buckets that collect photons. The more photons you can collect in your bucket the stronger the signal will be that is sent to the D/A converter.  This will require less amplification.  And of course will introduce less noise. Agreed?

But the exposure is related to the density of light collected and not the total amount of light collected. Noise is related to how much of the total light is collected.

And signal to noise ratio is based on the size of the pixels, not the sensor size. The light the sensor sees is the same, but bigger sensors generally have bigger pixels.  Right?

 The mistake Mr. Martin makes is he states that the f-number changes according to sensor size. That is not true.
Two images with the same f-stop, the same shutter speed, and the same ISO, will have the same exposure.  Period!

Signal to noise ratio is not determined by total light hitting the sensor, but by the light-per-area, which is identical given identical lenses and apertures. The cropped sensor receives no less light per area than a Full Frame. The signal-to-noise ratio is measured at that point not across the entire sensor.  But the image from a crop sensor has to be magnified more so it can be displayed at the same size as the FF. This means greater apparent noise in the final image.

[TTMartin]

---

@ebiggs1 wrote:

But the exposure is related to the density of light collected and not the total amount of light collected. Noise is related to how much of the total light is collected.

And signal to noise ratio is based on the size of the pixels, not the sensor size. The light the sensor sees is the same, but bigger sensors generally have bigger pixels.  Right?

---

Except it has nothing to do with pixel size, the 5DS has the same pixel size as a crop cameras do, but, has less noise for the entire picture than an APS-C camera because its sensor has MORE UNITS OF AREA. Not because it's pixels are bigger, they aren't. but because the sensor is bigger.  

So on a per pixel basis (per unit area) the 7D Mk II and the 5DS have the same amount of noise, because their pixel sizes are the same and they are receiving the same exposure. What DXO calls their screen measurement.

But, because the 5DS has more UNITS OF AREA (a bigger sensor) and it received more TOTAL LIGHT.  It has a higher signal to noise ratio for the entire photo. What DXO calls their print measurement.

[ebiggs1]

Oh I see you are a DXO fan.  I am not.  I understand where you are coming from better now.

I have made my case. Take it or leave it.

[TTMartin]

---

@ebiggs1 wrote:

Oh I see you are a DXO fan.  I am not.  I understand where you are coming from better now.

I have made my case. Take it or leave it.

---

I am NOT a DXO fan and think their measurements are biased due to improper decoding of  the CR2 file, but, sometimes their measurements are the best way to illiustrate a point or concept.

I believe I have made my case.

[ebiggs1]

Full disclosure I am guilty fo citing DXO when it suits or supports my case.  I really don't like DXO.  I will make a gallant effort to avoid doing that in the future.  DXO is agenda driven and really only shares info they want to.

I am not going to debate people who do cite them either.  At least we can remain cordial.  We simply have disagreed on this subject.  This is what I really took exception to, "... the 7D Mk II ... already captures one stop less total light tnan a full frame camera."   But I do believe we are saying nearly the same thing.  Only in a different way.

All the best to you.

[RobertTheFat]

---

@ebiggs1 wrote:

Full disclosure I am guilty fo citing DXO when it suits or supports my case.  I really don't like DXO.  I will make a gallant effort to avoid doing that in the future.  DXO is agenda driven and really only shares info they want to.

I am not going to debate people who do cite them either.  At least we can remain cordial.  We simply have disagreed on this subject.  This is what I really took exception to, "... the 7D Mk II ... already captures one stop less total light tnan a full frame camera."   But I do believe we are saying nearly the same thing.  Only in a different way.

All the best to you.

---

Here's one point on which we can possibly all agree:

Suppose we define "a" as the amount of incident light falling on an APS-C sensor. Assuming a constant aperture and strength of the light source, the amount of incident light falling on a full-frame sensor is 1.6a, because its surface area is 1.6 times as great. If one insists on expressing that difference in "stops", it's a lot closer to a half stop (1.414a) than it is to a full stop (2a). FWIW.