comparing lens + sensor size combos for low light

[DrLogic]

So I will start the question with an example. Given these two combinations with premium type lenses:

a6000 type camera (APS-C sensor) + 1670z @ F4

vs

Om-D EM EM5 type camera (m43 sensor) + 12-40 F2.8

The m43 sensor is half the size of the APS-C sensor, and typically the larger sensors are better for reduced noise in shadows and low light conditions for the same generation.

However, the m43 lens is a much faster lens in respect to the size of the sensor. Furthermore, the small sensor means that the DOF for the m43 sensor will be larger, thus one can employ a smaller aperture and not worry about parts of the image being out of focus in situations where there is no specific focal point.

I am not so much asking which lens/system is better; as they are both making different compromises it terms of sharpness/weight/size/DOF capabilities, etc. Both are awesome cameras.

Rather, I am more interested in how does one compare across formats. Presumably, the reason why the 1670z is F4 and the 12-40 is F2.8 is that designing a F2.8 for an APS-C sensor would result in a larger lens. Thus there is a trade off here. Do we go for a smaller sensor and smaller aperture number or a larger sensor with a higher aperture - what is better for low light when you bring the issue of lens size in the equation?

 

[Jerry R]

Interesting question. The size and weight of the two lenses is about the same. the f/2.8 will have about the DOF as the f/4, but an advantage in low light.

 

[MoreGooderPhotos]

One major advantage of FF I didn't see listed in your post: high ISO. A FF sensor will allow one to create much more usable shots at higher ISO levels than a smaller sensor.

Perhaps less important, but still important: Dynamic range. FF sensors have it in abundance.

If you're concerned about too shallow of a DOF with a FF you can always decrease the aperture. If that means you risk underexposing, either increase the shutter time or increase the ISO (or both).

So, in the end, FF sensors win the battle in a number of ways, except lose the battle when weight and cost are in the mix.

 

[Pixel Pooper]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

 

[DrLogic]

One major advantage of FF I didn't see listed in your post: high ISO. A FF sensor will allow one to create much more usable shots at higher ISO levels than a smaller sensor.

Perhaps less important, but still important: Dynamic range. FF sensors have it in abundance.

Agreed.

If you're concerned about too shallow of a DOF with a FF you can always decrease the aperture. If that means you risk underexposing, either increase the shutter time or increase the ISO (or both).

Yes, makes sense. The larger the sensor, the better quality with the higher ISOs levels, thus, one can bump up the ISO and use a higher aperture number. With smaller sensors one must rely on lower aperture, and keep the ISO constrained to the lower levels.

I try to avoid shooting at ISO 6400 and higher with my a6000, which requires very aggressive noise reduction.

So, in the end, FF sensors win the battle in a number of ways, except lose the battle when weight and cost are in the mix.

 

[DrLogic]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

 

[MoreGooderPhotos]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

 

[andrewD2]

One major advantage of FF I didn't see listed in your post: high ISO. A FF sensor will allow one to create much more usable shots at higher ISO levels than a smaller sensor.

Perhaps less important, but still important: Dynamic range. FF sensors have it in abundance.

They have one more stop of DR than APS-C given the same sensor generation. There is nothing magical about the dynamic range of a 35mm full frame sensor.
Crop a full frame image to the APS-C frame and the DR is exactly the same as an APS-C camera.
Or put another way, take two APS-C images and stitch them together to make a full frame image and you have the same DR as a full frame sensor.

Andrew

 

[DrLogic]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

I see, so in practical terms this means that if I shoot with a m43, APS-C and a FF camera (even a tiny phone sensor) at F2.8 at the same ISO the picture will look the same in terms of brightness. The background blur will be different, dynamic range will be different, but the brightness the same.

Where the larger sensor of say an A7 becomes more advantageous is when we are shooting at say F2.8, and it is dark (hand held thus limiting the shutter speed), and providing the thinner DOF fits with the composition, we can simply bump up the ISO level, which on the bigger sensor will be cleaner, and may not be a nice option on the smaller sensor.

In cases where DOF becomes an issue (like in a picture where I want more of the picture to be in focus in low light) then the cleaner ISO of the bigger sensor is negated by the bigger aperture number that we have to use to reduce the blur.

Does this imply that the main advantage of the bigger sensor, say an A7 over the a6000, comes into play when seperation is indeed required? Or when we are shooting at something in front of the bright sun.

 

[MoreGooderPhotos]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

I see, so in practical terms this means that if I shoot with a m43, APS-C and a FF camera (even a tiny phone sensor) at F2.8 at the same ISO the picture will look the same in terms of brightness. The background blur will be different, dynamic range will be different, but the brightness the same.

Where the larger sensor of say an A7 becomes more advantageous is when we are shooting at say F2.8, and it is dark (hand held thus limiting the shutter speed), and providing the thinner DOF fits with the composition, we can simply bump up the ISO level, which on the bigger sensor will be cleaner, and may not be a nice option on the smaller sensor.

In cases where DOF becomes an issue (like in a picture where I want more of the picture to be in focus in low light) then the cleaner ISO of the bigger sensor is negated by the bigger aperture number that we have to use to reduce the blur.

Does this imply that the main advantage of the bigger sensor, say an A7 over the a6000, comes into play when seperation is indeed required? Or when we are shooting at something in front of the bright sun.

Yes sir. I believe you've got it.

Although the differences between an A7 and an a6000 would be subtle. Pulling up the "shadows" of a subject when backlit can be a way to take advantage of the dynamic range of the sensor. If you really want to make full use of it, though, shoot in RAW or RAW+JPEG, then post process the RAW using the software of your choice. I use Light Room.

 

[lumigraphics]

For low light, I use my Canon 6D and one of my fast primes. Yes it's bigger than the mirrorless bodies but it's also in an entirely different league for quality.

Right tool for the job and all that stuff.

I will say that the a6000 has usable low-light quality if you pay attention to post-processing.

 

[Tmarz]

I have the Olympus em5 II with the 12-40 f2.8 and a NEX 6 but not the 16-70, I do have the 35f1.8. I can tell you that I can barely notice any difference in noise in low light. I am able to keep the shutter speed way down to keep a low ISO when shooting low light with the Olympus. I would imagine a A7 would be much better. From what I'm seeing the leap from micro four thirds and Aps c isn't that big of a leap. Getting a shallow DOF is a bit easier on the sony. Can't go wrong with either, I'm keeping both of them.

 

[Lab D]

So I will start the question with an example. Given these two combinations with premium type lenses:

a6000 type camera (APS-C sensor) + 1670z @ F4

vs

Om-D EM EM5 type camera (m43 sensor) + 12-40 F2.8

I don't know as much as about the EM5 (older model) but the E-M1 in most cases would top the A6000.

At most ISOs the DR for the EM1 and A6000 are near identical, and Noise is less than 1 stop Therefore the EM1 would often be almost a stop better for DR and slightly better for noise with the lenses you mentioned.

Other lenses might yield different results.

The m43 sensor is half the size of the APS-C sensor, and typically the larger sensors are better for reduced noise in shadows and low light conditions for the same generation.

However, the m43 lens is a much faster lens in respect to the size of the sensor. Furthermore, the small sensor means that the DOF for the m43 sensor will be larger, thus one can employ a smaller aperture and not worry about parts of the image being out of focus in situations where there is no specific focal point.

I am not so much asking which lens/system is better; as they are both making different compromises it terms of sharpness/weight/size/DOF capabilities, etc. Both are awesome cameras.

Rather, I am more interested in how does one compare across formats. Presumably, the reason why the 1670z is F4 and the 12-40 is F2.8 is that designing a F2.8 for an APS-C sensor would result in a larger lens. Thus there is a trade off here. Do we go for a smaller sensor and smaller aperture number or a larger sensor with a higher aperture - what is better for low light when you bring the issue of lens size in the equation?

As I mentioned above, in your scenario the E-M1 would be better. Also, from experience in low light it is more reliable focusing, but that is a different topic.

 

[AHM]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

 

[Pieterbaan]

Forget the IQ difffernces. Both camera's and lenses are great and will deliver stunning pictures. What is way more important is the feel of the camera. Go to a shop and rty them out. feel them, handle them, when possible take pictures with them (not to compair, but to feel how the cameras work. Try to change settings, look at the menu etc. gofor the camera you find handling best.

I know this is a gear forum and people are talking about gear, but the IQ of these cameras and lenses is that high that in normal world pictures (printed o seen on your big screen TV) are very close so no need to think about that.

Others here have told what (in theory) is the best combination, but when you go primes things will be a bit different again. Most primes on both systems are arround f/1.8 so when using those primes the A6000 might be the best camera (again mainly when pixel peeking so in real life pictures not that much of a difference...) What is maybe of a big importance for you is the following;

What system has the lenses you want or need?
What system will you take with you the most (is one system (much) larger then the other, take lenses in this too)
What system do you like best (do you like the A6000 formfactor or the formfactor of the m43 camera of your choice)
What is the price of a complete system?

 

[DrLogic]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

I believe this is the section you are referring to. Quote (http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2):

The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity.

And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image. It's likely that the large sensor camera will be bigger, heavier and more expensive, but it should provide cleaner images.

The flip-side of this is that, if you can fit a faster lens to a smaller format sensor or use a slower shutter speed then you can match the total light available to the larger system and gain similar image quality. However, this only really works in low light, where you're limited by the availability of light. In bright lighting conditions, where you're more worried about highlights clipping than you are about noise swamping the shadows, you can't simply open the aperture up to match a larger sensor's total light - you'll just end up over-exposing.

 

[AHM]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

I believe this is the section you are referring to. Quote (http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2):

The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity.

And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image. It's likely that the large sensor camera will be bigger, heavier and more expensive, but it should provide cleaner images.

The flip-side of this is that, if you can fit a faster lens to a smaller format sensor or use a slower shutter speed then you can match the total light available to the larger system and gain similar image quality. However, this only really works in low light, where you're limited by the availability of light. In bright lighting conditions, where you're more worried about highlights clipping than you are about noise swamping the shadows, you can't simply open the aperture up to match a larger sensor's total light - you'll just end up over-exposing.

Yes, exactly. And this statement:

The equivalent aperture tells you what aperture on a full frame lens would give the same depth-of-field and the same total light as the one you're assessing.

 

[Jerry R]

The discussion is about the same f/2.8 and f/4 f-stops not aperture.

--
Sony R1, NEX C3 & 5R + Zeiss 24mm, 16-70, & FE 70-200 Lenses, Nikon V1 + 10-30 & 30-110 lenses.

 

[MoreGooderPhotos]

Suggested reading:

http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care

 

[lumigraphics]

To get the equivalent aperture you multiply by the crop factor of 1.31, so the f/2.8 lens on M43 is equivalent to f/3.67 on APS-C, which means the M43 should be 1/4 stop better in low light and will have 1/4 stop less DOF.

So equivalence is not only applicable on DOF (which I knew), but also in terms of exposure? That is, if I have both cameras set at say F4 and at the same ISO, the picture will be darker in m43?

I suppose thats an easy question to answer if only I had a m43 + APS-C camera, or APS-C camera + FF one, I could take two pics and compare.

F2.8 is F2.8. The aperture equivalence pertains to DoF, and has nothing to do with exposure. Aperture is one third of the exposure triangle, Aperture, shutter speed and ISO.

For example, high end smart phones have itty bitty sensors but have "wide open" apertures such as F2.0. However, if you do a macro shot or portrait with them it will be impossible to get subject isolation as one would with a larger sensor. Heck.... tiny cell phone sensors make for some really good landscape shots if the light is good enough to avoid high ISO. That's because the DoF is massive by comparison, so it is easy to get everything in focus.

No, Pixel Pooper is correct. Read the DPReview article on equivalence. It's basic physics.

I believe this is the section you are referring to. Quote (http://www.dpreview.com/articles/2666934640/what-is-equivalence-and-why-should-i-care/2):

The thing that complicates matters is ISO. ISO ensures that, if you expose a sensor to a given light intensity for a given amount of time, then you will get a certain brightness in your final (JPEG) image. Because it's based on intensity of light, it means that ISO depends on F-number, not equivalent aperture. This means that, a Four Thirds camera with a 50mm f/2 lens at ISO100 should produce a JPEG of the same brightness as a Full frame camera with a 100mm f/2 lens at ISO100 and, set to the same F-number and shutter speed, even though its smaller sensor means it is receiving 1/4 as much total light.

ISO is useful, in that it means that the same set of exposures work across all cameras (and frankly, it'd get confusing, otherwise). However, it ends up disguising how much total light each system gets. Since the light intensity is the same (per square mm), the Full Frame camera will receive four times as much light as the Four Thirds camera, during those exposures, because it has four times the sensor area, all experiencing that same intensity.

And this means that, for the same shutter speed, F-number and ISO, the camera with the largest sensor will have more total light to measure. And, unless the large sensor is significantly worse than the smaller one, it will produce a cleaner, less noisy image. It's likely that the large sensor camera will be bigger, heavier and more expensive, but it should provide cleaner images.

The flip-side of this is that, if you can fit a faster lens to a smaller format sensor or use a slower shutter speed then you can match the total light available to the larger system and gain similar image quality. However, this only really works in low light, where you're limited by the availability of light. In bright lighting conditions, where you're more worried about highlights clipping than you are about noise swamping the shadows, you can't simply open the aperture up to match a larger sensor's total light - you'll just end up over-exposing.

Yes, exactly. And this statement:

The equivalent aperture tells you what aperture on a full frame lens would give the same depth-of-field and the same total light as the one you're assessing.

The whole "total light" business is WRONG WRONG WRONG.

Remember that image size changes, so that your "4 times" is spread across a larger area to create the same image on the sensor.

There are other reasons that a larger sensor gives better IQ, but the total amount of light hitting it is NOT the reason.