Reading mode: Light Dark

Aperture Equivalent when using E-Nex lenses on Sony A7/7r

Go to last post
Shahrooz51

Shahrooz51

Member
Messages
37
Reaction score
6
Location
Orange County, CA, US
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
 
D Cox said:
Christof21 said:
The sensor size has a big impact on the light received by the sensor.
Click to expand...
The extra light around the edges gives you a bigger picture covering a wider angle. (Assuming the lens can cover.)
D Cox said:
Whatever your light meter says, the bigger sensor recieves much more light when shooting with the same f-number !
Click to expand...
But it receives the same the same illuminance (light per square mm), so the exposure is the same.
Click to expand...
The exposure is the same but it doesn't give you the same results. By same result I mean equivalent angle of view, depth of field, dynamic range and overall noise at a given print size.
 
Christof21 said:
Lightshow said:
Christof21 said:
antares103 said:
There are two characteristics inferred by the f/ number of a lens, the aperture and how much light it lets in, and the depth of field at a given distance.

The first is rather fixed. A calculation based on the actual focal length. F/4 is f/4 and will allow in the same amount of light regardless of focal length, equivalent focal length, or sensor size etc. (minor fluctuations can happen due to rounding values or lens coatings, but these are negligible).

Then you have depth of field and how blurry the back ground is. At the same distance and aperture, a lens on FF and a lens on APSC will have the same back ground blurriness. However, since the APSC has a smaller crop, you will need to back the camera up to achieve the same composition. The backing of the camera will increase the depth of field, as DoF is a function of lens to subject distance.

Alternatively, you can keep the same composition by using a wider lens on the APSC camera. DoF will increase as it is also a function of focal length.

So "f/4" is a descriptor in light gathering properties more than a descriptor in DoF as DoF will change with sensor size (and always has, even back in film, not just with APSC sensors).

You can say, however, the depth of field equivalence of a lens on APSC is 1.5 times that of FF, if you keep the composition the same. This is far different than saying an f/4 lens is an f/5.6 lens on APSC, which is mathematically and empirically incorrect.
Click to expand...
Click to expand...
Agreed.
Member said:
Member said:
--
Film is a four letter word
Click to expand...
f4 on APS-C is equivalent to f6 on FF in terms of dof AND light.
Click to expand...
Nope
Click to expand...
The equivalent aperture not only tells you how much depth-of-field you get, on a different system, it also tells you how much total light you'll get.
Click to expand...
Actually, aperture value tells you only a part of the story about total light. The other part is told by time value (shutter speed). Those two combined give you exposure. And speaking of which, an f/4 is f/4 when it comes to exposure. An f/4 does not become f/6. It remains f/4.
 
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
 
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
 
Christof21 said:
Lightshow said:
Christof21 said:
antares103 said:
There are two characteristics inferred by the f/ number of a lens, the aperture and how much light it lets in, and the depth of field at a given distance.

The first is rather fixed. A calculation based on the actual focal length. F/4 is f/4 and will allow in the same amount of light regardless of focal length, equivalent focal length, or sensor size etc. (minor fluctuations can happen due to rounding values or lens coatings, but these are negligible).

Then you have depth of field and how blurry the back ground is. At the same distance and aperture, a lens on FF and a lens on APSC will have the same back ground blurriness. However, since the APSC has a smaller crop, you will need to back the camera up to achieve the same composition. The backing of the camera will increase the depth of field, as DoF is a function of lens to subject distance.

Alternatively, you can keep the same composition by using a wider lens on the APSC camera. DoF will increase as it is also a function of focal length.

So "f/4" is a descriptor in light gathering properties more than a descriptor in DoF as DoF will change with sensor size (and always has, even back in film, not just with APSC sensors).

You can say, however, the depth of field equivalence of a lens on APSC is 1.5 times that of FF, if you keep the composition the same. This is far different than saying an f/4 lens is an f/5.6 lens on APSC, which is mathematically and empirically incorrect.
Click to expand...
Click to expand...
Agreed.
Click to expand...
Click to expand...
 
EinsteinsGhost said:
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
Click to expand...
Because you're stuck looking at pixels and declaring how everyone who looks at the whole image is wrong about total noise.
 
dotborg said:
EinsteinsGhost said:
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
Click to expand...
Because you're stuck looking at pixels and declaring how everyone who looks at the whole image is wrong about total noise.
Click to expand...
There is no need to crop an image to pixel level to see my point. Take a FF image, crop to APS-c. Would you see more noise? Why?
 
EinsteinsGhost said:
dotborg said:
EinsteinsGhost said:
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
Click to expand...
Because you're stuck looking at pixels and declaring how everyone who looks at the whole image is wrong about total noise.
Click to expand...
There is no need to crop an image to pixel level to see my point. Take a FF image, crop to APS-c. Would you see more noise?
Click to expand...
If you print the two images the same size or scale them to the same size for viewing on your PC then yes.
EinsteinsGhost said:
Why?
Click to expand...
Because you're making the noise larger and more apparent. Another way to look at it is that when you scale an image down, you average the pixels together, averaging out the noise. If you're not scaling it down as much then you're not "hiding" as much noise as you did before.
 
dotborg said:
EinsteinsGhost said:
dotborg said:
EinsteinsGhost said:
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
Click to expand...
Because you're stuck looking at pixels and declaring how everyone who looks at the whole image is wrong about total noise.
Click to expand...
There is no need to crop an image to pixel level to see my point. Take a FF image, crop to APS-c. Would you see more noise?
Click to expand...
If you print the two images the same size or scale them to the same size for viewing on your PC then yes.
Barugon said:
Why?
Click to expand...
Because you're making the noise larger and more apparent. Another way to look at it is that when you scale an image down, you average the pixels together, averaging out the noise. If you're not scaling it down as much then you're not "hiding" as much noise as you did before.
Click to expand...
And this has been exactly the point I've been making thru several threads on the subject. What we're seeing is an effect of enlargement, not of difference in exposure or total light.

If more total light resulted in "superior" exposure that somehow reduced noise, we should see that effect in crops enlarged as well.
 
forpetessake said:
B.t.w., there is an interesting and very practical corollary of the lens equivalence:

* you can convert an FF lens to its equivalent APS-C lens by using a 1.5x focal reducer -- that's perhaps everybody knows;

* what's less known, you can do the opposite as well, you can convert an APS-C lens to its equivalent FF lens by using a 1.5x teleconverter.

So if you take your 18-105mm f/4 APS-C lens and attach a 1.5x teleconverter, you'll end up with a 27-157.5mm f/6 FF lens. You no longer need to use the crop on your A7R, the lens will cover the full frame. Now, why would you do that if you end up with the equivalent image: the same FOV, DOF, noise? -- There are advantages nonetheless: you get more pixels, and you get a better dynamic range at the base ISO.
Click to expand...
forpetessake said:
I hadn't ever thought about that. But is makes sense. Have you done this? It seems like it wold open up a greater range of lenses for the 7 series of Alphas at least until Sony starts producing more FF lenses.
Click to expand...
 
EinsteinsGhost said:
Amen!

Although, the issue mainly comes from resistance to fact that noise is not any different, just more visible from smaller sensors due to need for greater enlargement to same print/viewing size... and promotion that it is because of more light gathering on FF (which, ironically, they fail to realize REQUIRES more light for same exposure). But, they happen to take the popular route, and repeating it enough has led to that belief, of f-stop not being f-stop for exposure values rather than some kind of equivalence.
Click to expand...
I agree. Using a FF lens on an a7 and on an a6000, the amount of light that hits the portion of the FF sensor that is located exactly where the crop season will ge the same as the light that hits the crop sensor. However, because the effective focal length has changed the Bokeh and the compression of images in the background will be different and therefore the two pictures will be different even if you crop the full frame to the exact picture that was taken by the crop sensor.

I would like to recommend this youtube video for a pretty good explanation on what has been discussed in this thread. Keep in mind this is not meant for EinsteinGhost only but for everyone who has taken part in this thread. Here is the link.

That's my story and i am sticking to it.
 
EinsteinsGhost said:
dotborg said:
EinsteinsGhost said:
dotborg said:
EinsteinsGhost said:
dotborg said:
blue_skies said:
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
It is hidden in thread somewhere, but here are the main points:

Aperture is a LENS property. It is defined as the focal length (FL) divided by its maximum aperture (AE). This is unrelated to sensors (or even camera types).

Exposure is also regardless of sensors. f/4, ISO 400, 1/100th is the SAME exposure on all cameras, from your cell phone to your medium format and beyond.

This is why light-meters work - they simply tell you proper settings based on measured light (and method).

So, if all sensors expose the same - do they all receive the same amount of light?

Yes, on a per measurement of area basis. (Typically not pixel, because pixel sites are not the same size). But on a TOTAL AREA basis, a larger sensor receives more light, given the SAME exposure.

Of course, a larger sensor which uses the same exposure settings will have less noise (because of more light) and less DOF (because of less enlargement for viewing full image).

Now, to make the larger sensor equivalent to the smaller sensor, you have to add noise (higher ISO) and add DOF (smaller aperture). As the formulas work, this goes together with the crop factor.

So, if I expose equal between APS-C and FF, FF will have less DOF and less noise.

If I expose equivalent between APS-C and FF, both will have same DOF and same noise.

In the spirit of the latter, speaking to the OP's question, yes, you would capture with f/6 on the FF (1.5x) when comparing to f/4 on the APS-C. You would also shoot at (just over) double the ISO (1 stop) the match the equivalent exposure (same DOF, same noise) (which then makes the exposure - i.e. light per area - the same again).

Of course, you don't have to. Using the equal exposure is perfectly fine, except that the FF image will show less DOF and less noise.

(I am assuming equivalent FOV - the FL also is subject to the crop, and this could change the light input. If the same FOV, this is a constant).
Click to expand...
Precisely.
Click to expand...
Doesn't explain WHY you would see more noise if you crop a FF image with supposedly less noise, does it? Hint: See your own premise of comparing multiple formats at same print/viewing size.

It has NOTHING to do with total light. If more total light reduced noise, it should be seen in cropped FF image, and yet, you don't (or, should I say, I don't).
Click to expand...
Because you're stuck looking at pixels and declaring how everyone who looks at the whole image is wrong about total noise.
Click to expand...
There is no need to crop an image to pixel level to see my point. Take a FF image, crop to APS-c. Would you see more noise?
Click to expand...
If you print the two images the same size or scale them to the same size for viewing on your PC then yes.
EinsteinsGhost said:
Why?
Click to expand...
Because you're making the noise larger and more apparent. Another way to look at it is that when you scale an image down, you average the pixels together, averaging out the noise. If you're not scaling it down as much then you're not "hiding" as much noise as you did before.
Click to expand...
And this has been exactly the point I've been making thru several threads on the subject. What we're seeing is an effect of enlargement, not of difference in exposure or total light.

If more total light resulted in "superior" exposure that somehow reduced noise, we should see that effect in crops enlarged as well.
Click to expand...
I specifically said that you had to use a different exposure to get the same results.
 
Henry, take a few minutes and watch this video. It is very enlightening.
It is a very good explanation on youtube by a photographer on different sized sensors with pictures to back up what he says.

Enjoy watching.
 
Dotborg, please watch this youtube video. It really explains different sized sensors very well and backs up the math involved with examples. If might say exactly what you believe or it might not. But it will help everyone esplain the truth in a readily understandable manner. here is the link:
 
Shahrooz51 said:
Hi,

I have a A7r,it is really impressive camera. Because of lake of FE lenses,I want to buy E-mount (NEX) lenses and use with my A7r while I am aware of their crop factors.Also,I have read some articles about equivalent focal length and aperture value when we have crop sensor.My question is if we use E-Nex lenses on A7/7r camera do we have equivalent aperture too? For example,If I use a 18-105 mm f4 on my A7r,my lowest aperture will be f6?

Thank You.
Click to expand...
There have been a lot of heated debates going on in this thread. if you are still watching it and are still interested in the truth of the matter watch this youtube video. This photographer (a guy who gets paid to take pictures and write books about photography did a video that explains all about exposures and DOF and everything else about various sensor sizes and crop factors on lenses and light. Watch and learn.
I have watched it twice already but cannot explain it like this guy does. And he backs up what he says with pictures taken with different sensor sizes.

Have fun and learn about taking good pictures.
 
dg8r said:
Henry, take a few minutes and watch this video. It is very enlightening.
It is a very good explanation on youtube by a photographer on different sized sensors with pictures to back up what he says.

Enjoy watching.
Click to expand...
Tony Northrup's lengthy video? It has been discussed here previously, but it doesn't add anything new to the discussion.

We are past the point of equivalence, and are (or at least some of us) discussing sensor, or sensor crop, efficiency, and, unless you want to ballpark it, there are simply too many variables to take into account, the least being true (and comparable) versus stated (and camera reported) ISO.

The point of debate is simply, if you consider the APS-C sensor one pixel, and the FF two pixels.

If you crop the FF sensor down the APS-C size, you'd end up with just one pixel, and you'd get the same equal exposure and everything. The FF sensor (size) benefit is lost.

If you don't crop, you can use equivalent exposure, and, simply, two pixels is better than one :)

Replace the one pixel by 'total active area' and you have the same math. Problem is that smaller sensors and larger sensors follow different design rules, and we end up arguing over variances, not over the main differences.

DOF and ISO seem largely misunderstood - they all are part of exposure. We do not have 'iso-less' sensors yet, although we are moving there. Typically, if you shoot a scene you want to control FOV, aperture and shutter speed. ISO then follows and should not get in the way. Most of us end up compromising because we cannot use the aperture and shutter speed combination that we'd really like to, so one, or the other, has to be less than what we'd liked.

But, in terms of equivalence, sensors of different sizes can be made to appear very similar by simply finding the FOV, aperture (DOF), ISO (noise) and shutter speeds, that are equivalent. For a larger sensor, this means stop-down and raise ISO. For a smaller sensor it means open wide and lower ISO.

Of course, smaller sensors are lower ISO limited, and the noise floor is rather low. But if you like DOF, your cell phone beats the FF in most daytime shoots :)

Cropping a sensor (by using the wrong lens) is really no different than using a smaller size sensor. Sure, you can analyze the QE, sensor readout efficiency, total active area, active area responsiveness, and more, but it is, again, analyzing the variances, not the main factors.

Much in this thread (and prior ones) has been said that is all valid. And goes way past the OP's question and answers to that....

Also, since the introduction of cameras such as the A7s and 1Df, a lot of sensor-size observations no longer hold up - no small sensor camera can match these 'low light monsters'.... :)

--
Cheers,
Henry
 
Last edited:
Lightshow said:
Christof21 said:
Lightshow said:
Christof21 said:
antares103 said:
There are two characteristics inferred by the f/ number of a lens, the aperture and how much light it lets in, and the depth of field at a given distance.

The first is rather fixed. A calculation based on the actual focal length. F/4 is f/4 and will allow in the same amount of light regardless of focal length, equivalent focal length, or sensor size etc. (minor fluctuations can happen due to rounding values or lens coatings, but these are negligible).

Then you have depth of field and how blurry the back ground is. At the same distance and aperture, a lens on FF and a lens on APSC will have the same back ground blurriness. However, since the APSC has a smaller crop, you will need to back the camera up to achieve the same composition. The backing of the camera will increase the depth of field, as DoF is a function of lens to subject distance.

Alternatively, you can keep the same composition by using a wider lens on the APSC camera. DoF will increase as it is also a function of focal length.

So "f/4" is a descriptor in light gathering properties more than a descriptor in DoF as DoF will change with sensor size (and always has, even back in film, not just with APSC sensors).

You can say, however, the depth of field equivalence of a lens on APSC is 1.5 times that of FF, if you keep the composition the same. This is far different than saying an f/4 lens is an f/5.6 lens on APSC, which is mathematically and empirically incorrect.
Click to expand...
Click to expand...
Agreed.
Lightshow said:
Lightshow said:
--
Film is a four letter word
Click to expand...
f4 on APS-C is equivalent to f6 on FF in terms of dof AND light.
Click to expand...
Nope
Click to expand...
The equivalent aperture not only tells you how much depth-of-field you get,
Click to expand...
DOF is the same, it's directly related to the focal length, aperture and distance to the subject, moving the camera(to get the same framing) is what changes the DOF.
Lightshow said:
on a different system, it also tells you how much total light you'll get.
Click to expand...
But there is no point in trying to figure out the total(sum) amount of light
Click to expand...
I think you should care about the total quantity of light for the resulting image !!! It is what matters because the amount of noise in the image is depends on this quantity. Instead of comparing the f-number which is meaningless, you should consider the total amount of light.
Lightshow said:
, the camera doesn't measure exposure that way.
Click to expand...
Lightshow said:
Select an area on a 4/3 sized sensor, then using the same area on an APS-C and FF sensor, the amount of light (photons) hitting that area will not change if the exposures are the same and you haven't moved the camera, all that happens is the projected image is cropped
Click to expand...
Everybody agrees with this on this thread, people keep repeating that f4=f4. This is not the point.
Lightshow said:
.
Lightshow said:
Lightshow said:
.
Lightshow said:
What is important (for the final resulting image) is the total light collected on the sensor.
Click to expand...
The total amount of light for a given area, not the total, or else cropping in post will change the exposure at the time of capture.

The properties of the lens don't change when the sensor size changes.
Lightshow said:
In equivalent settings, the total light is the same ( and thus the same noise).

So, equivalent aperture (with equivalent settings) give the same results in nearly every aspect !!!!
Click to expand...
--
I don't have any AF lenses, so if I want a picture, I have to do more than squeeze a button.
http://www.flickr.com/photos/lightshow-photography/
My lenses:
http://www.fredmiranda.com/forum/viewprofile.php?Action=viewprofile&username=LightShow
Click to expand...
Click to expand...
--
I don't have any AF lenses, so if I want a picture, I have to do more than squeeze a button.
http://www.flickr.com/photos/lightshow-photography/
My lenses:
http://www.fredmiranda.com/forum/viewprofile.php?Action=viewprofile&username=LightShow
Click to expand...
 
Christof21 said:
Lightshow said:
Christof21 said:
Lightshow said:
Christof21 said:
antares103 said:
There are two characteristics inferred by the f/ number of a lens, the aperture and how much light it lets in, and the depth of field at a given distance.

The first is rather fixed. A calculation based on the actual focal length. F/4 is f/4 and will allow in the same amount of light regardless of focal length, equivalent focal length, or sensor size etc. (minor fluctuations can happen due to rounding values or lens coatings, but these are negligible).

Then you have depth of field and how blurry the back ground is. At the same distance and aperture, a lens on FF and a lens on APSC will have the same back ground blurriness. However, since the APSC has a smaller crop, you will need to back the camera up to achieve the same composition. The backing of the camera will increase the depth of field, as DoF is a function of lens to subject distance.

Alternatively, you can keep the same composition by using a wider lens on the APSC camera. DoF will increase as it is also a function of focal length.

So "f/4" is a descriptor in light gathering properties more than a descriptor in DoF as DoF will change with sensor size (and always has, even back in film, not just with APSC sensors).

You can say, however, the depth of field equivalence of a lens on APSC is 1.5 times that of FF, if you keep the composition the same. This is far different than saying an f/4 lens is an f/5.6 lens on APSC, which is mathematically and empirically incorrect.
Click to expand...
Click to expand...
Agreed.
Member said:
Member said:
--
Film is a four letter word
Click to expand...
f4 on APS-C is equivalent to f6 on FF in terms of dof AND light.
Click to expand...
Nope
Click to expand...
The equivalent aperture not only tells you how much depth-of-field you get,
Click to expand...
DOF is the same, it's directly related to the focal length, aperture and distance to the subject, moving the camera(to get the same framing) is what changes the DOF.
Member said:
on a different system, it also tells you how much total light you'll get.
Click to expand...
But there is no point in trying to figure out the total(sum) amount of light
Click to expand...
I think you should care about the total quantity of light for the resulting image !!! It is what matters because the amount of noise in the image is depends on this quantity. Instead of comparing the f-number which is meaningless, you should consider the total amount of light.
Click to expand...
Let us assume your case to be true. Then, you should also expect APSc crop from a FF sensor to maintain the FF advantage. Does it?
Member said:
Member said:
, the camera doesn't measure exposure that way.

Select an area on a 4/3 sized sensor, then using the same area on an APS-C and FF sensor, the amount of light (photons) hitting that area will not change if the exposures are the same and you haven't moved the camera, all that happens is the projected image is cropped
Click to expand...
Everybody agrees with this on this thread, people keep repeating that f4=f4. This is not the point.
Member said:
.
Member said:
Member said:
.
Member said:
What is important (for the final resulting image) is the total light collected on the sensor.
Click to expand...
The total amount of light for a given area, not the total, or else cropping in post will change the exposure at the time of capture.

The properties of the lens don't change when the sensor size changes.
Member said:
In equivalent settings, the total light is the same ( and thus the same noise).

So, equivalent aperture (with equivalent settings) give the same results in nearly every aspect !!!!
Click to expand...
--
I don't have any AF lenses, so if I want a picture, I have to do more than squeeze a button.
http://www.flickr.com/photos/lightshow-photography/
My lenses:
http://www.fredmiranda.com/forum/viewprofile.php?Action=viewprofile&username=LightShow
Click to expand...
Click to expand...
--
I don't have any AF lenses, so if I want a picture, I have to do more than squeeze a button.
http://www.flickr.com/photos/lightshow-photography/
My lenses:
http://www.fredmiranda.com/forum/viewprofile.php?Action=viewprofile&username=LightShow
Click to expand...
Click to expand...
 
dg8r said:
EinsteinsGhost said:
Amen!

Although, the issue mainly comes from resistance to fact that noise is not any different, just more visible from smaller sensors due to need for greater enlargement to same print/viewing size... and promotion that it is because of more light gathering on FF (which, ironically, they fail to realize REQUIRES more light for same exposure). But, they happen to take the popular route, and repeating it enough has led to that belief, of f-stop not being f-stop for exposure values rather than some kind of equivalence.
Click to expand...
I agree. Using a FF lens on an a7 and on an a6000, the amount of light that hits the portion of the FF sensor that is located exactly where the crop season will ge the same as the light that hits the crop sensor. However, because the effective focal length has changed the Bokeh and the compression of images in the background will be different and therefore the two pictures will be different even if you crop the full frame to the exact picture that was taken by the crop sensor.
Click to expand...
Focal length does not change. But if you implied FOV, you're already maintaining that by comparing 160mm equiv for it (105mm on APS-c). DOF will be affected. But, exposure will not be. If it was 1/1000s, f/4 at ISO 100 for FF, it will be the same for any other format. Or, do you expect FF image to be overexposed relative to APSc by a stop?
dg8r said:
I would like to recommend this youtube video for a pretty good explanation on what has been discussed in this thread. Keep in mind this is not meant for EinsteinGhost only but for everyone who has taken part in this thread. Here is the link.

That's my story and i am sticking to it.
Click to expand...
 
You must log in or register to reply here.

Keyboard shortcuts

f
Forum
m
My threads
Mobile site
About
Editorial content
Cameras & Lenses
Community
All content, design, and layout are Copyright © 1998–2025 Digital Photography Review All Rights Reserved.
Reproduction in whole or part in any form or medium without specific written permission is prohibited.
When you use DPReview links to buy products, the site may earn a commission.
©GPS Media - Guides, Products, Services.
Back
Top