Is Full Frame sharper than APS-C? My answer here

[Don Haines]

good gravy people..... there is no practical answer to the question... cameras are systems.... it's not just the sensor.... You have sensors, lenses, and software. In theory, a simillarly designed lens of the appropriate focal length, F stop, shutter, materials, and build for APS-C and one for FF, should act the same..... but good luck finding a pair. Every model of camera will have different algorithms..... with different processor speeds and different features there are different demands on the camera and also, software gets optimized and bugs get fixed.... good luck finding two camera models that run the same software. Sensors are constantly evolving.... for the comparison to be meaningful they would have to be built with the same age of technology.

And assuming you were able to find find two truly comparable systems, just what do you mean by sharpness?
Are you talking sharpness of a pixel, sharpness of an image, or sharpness per mm of sensor? These are going to give you three different answers. If you are talking about sharpness per mm of sensor my iPad beats any FF or APS-C sensor hands down.... An argument without defined parameters is just an exercise in frustration and hurt feelings.

[TheSuede]

Full frame isn't sharper than APS, that's basically a metaphorical question. The edges of the naturalization of the silicon surface are treated the same, so it's just as easy to get paper cuts from handling a naked APS sensor edge as an FF sensor edge. I know from personal experience...

And this magnification discussion is rather confused, let's just go through the entire image process chain:

1) Reality (in glorious smello-vision 3D!)
2) Optical projection 3D >> 2D
3) We digitize that 2D projection into a "pixel resolution" - in this case via a digital camera sensor
4) this "resolution" is presented - either on screen or on print.

Comparing two different camera formats means that we need to change some stuff to equalize points 2) and 3). We want to keep 1) and 4) constant! The reality (model, object, scene) is the same, we want the end result image to be the same.

We need to change the inter-operation scales. We use lower object magnifications - a shorter focal length - in step 2>3. The image pixel is unitless, just a datapoint in the grid of data that makes a digital image. To keep the quality of the intermediate digital image (3) constant, we need to keep per-pixel sharpness and noise constant.

Using the same lens at the same aperture on both systems won't make that happen. Optical defects spread over more pixels in the smaller sensor - since those pixels are physically smaller. But the object resolution - how much detail on the target that you can see - can never get worse with smaller pixels, it can only get better. This is the crop effect birders are after. Target resolution.

Using a 1.5x shorter lens at the same aperture value on the smaller system will make the field of view the same, but DoF will be deeper (more about this later!). Now if the lens is also 1.5x sharper, has the same MTF at 45lp/mm as the larger lens has at 30lp/mm, object resolution will be equal - and since a pixel is a pixel is a pixel, digitized image resolution will also be equal. But noise will be stronger (due to the deeper DoF!).

To get noise equal too, you need to keep the amount of captured light energy equal. And to get the light throughput per second equal, we need to have the same entry pupil diameter on both systems. The entry pupil is what "gathers light" from from the scene from the optical system's point of view - if light is to reach the sensor, it has to pass through this aperture. The nominal entry pupil is focal length divided by f/# - that's why it's named an F-stop.
Small "f" for focal length, and the hash-tag "#" sign signifies unitless result. A 50mm F2.0 then has a nominal 50mm/2.0 = 25mm front pupil. To get the same field of view on APS we need a ~35mm lens. We still need a 25mm front pupil, so the F-stop needs to be 35mm(f) / 25mm(d) = 1.4(#) = F1.4

So if you could make a 35F1.4 that's 1.5x sharper than a 50F2.0, everything would be fine. But that's the problem - that's a very hard thing to do. AND you'd need an APS camera with 1.5^2 = 2.25x lower base ISO to keep light energy storage capacity the same, since ISO is area based.

[TheSuede]

good gravy people..... there is no practical answer to the question... cameras are systems.... it's not just the sensor.... You have sensors, lenses, and software. In theory, a simillarly designed lens of the appropriate focal length, F stop, shutter, materials, and build for APS-C and one for FF, should act the same..... but good luck finding a pair. Every model of camera will have different algorithms.....
(.../some shortening applied/...)
And assuming you were able to find find two truly comparable systems, just what do you mean by sharpness?
Are you talking sharpness of a pixel, sharpness of an image, or sharpness per mm of sensor? These are going to give you three different answers. If you are talking about sharpness per mm of sensor my iPad beats any FF or APS-C sensor hands down.... An argument without defined parameters is just an exercise in frustration and hurt feelings.

This is the practical, sane and pragmatic answer. I whole-heartedly agree

It's up to each and every one for themselves to find the SYSTEM that suits their needs.
For me that "best answer" is sometimes APS, sometimes 1" sensors and sometimes also digital medium format (though that need has fallen drastically the latest three or four years, since the arrival of 20MP+ FF cameras).

[bdunbar79]

Well if I can answer with a question. When you look at your picture at 100% on your computer do you think you are looking at the pixels from your sensor ?

Why would you answer with a question?

Socrates used to.

[East Wind Photography]

Nope that's not what I'm seeing comparing the same shots between a 5D3 and a 7D.  The 5D3 cropped to the same size as the 7D resolves a tad more detail in RAW comparisons.  I dont even use the 7D anymore.

This assumes that you also always print the full frame. For some cropping is always required.  If you crop the same image to the same composition your results may vary.  We don't always have the luxury of filling the frame especially when using a prime lens in less than adequate quarters.

If you're shooting side-by-side with a 7D and a 20mm prime, a 5DIII and a 35mm prime, and an 8x10 view camera and a 250mm prime, you're going to be cropping away the same proportional amount to get the same composition from each, rendering the cropping point moot.

If you're distance-limited, sure, it can make a difference...but generally not at much as most people tend to think. If that little birdie only fills an eighth of your frame with the 800mm f/5.6 on the 5DIII, you'll get better results putting the lens on the 7D, but not hugely better. The real answer is to improve your tracking skills so you can get closer and fill the frame, with whatever camera / lens combination.

Cheers,

b&

[Don Haines]

it does until Canon brings out a  24x36 camera with high pixel density then you can crop as it suits you

yes, but if you built an APS-c sensor at the same pixel density as the sensor in an Ipad you could have an 216Mpixel sensor......

[AprilForever]

APS-C solves a lot of problems full frame creates...

[Meh]

Well if I can answer with a question. When you look at your picture at 100% on your computer do you think you are looking at the pixels from your sensor ?

Why would you answer with a question?

Socrates used to.

Socrates gets some leeway.  People who make unclear or unsubstantiated statements aren't generally afforded the luxury of evading questions in that fashion.

[Meh]

Some of you are confusing enlargement and sensor resolution.  Do you know who you are?

well it is a optical question and it is hard to get a APS lens that are 1,6 times better than a 24x36mm lens regarding resolution, contrast etc. If  there was one there will  not be any differences results wise between a 24MP APS sensor and a 24Mp 24x36mm sensor and if the signal/noise ratio was the same from the two sensors

What exactly do you mean by an "APS lens that is 1.6 times better than 24x36mm lens"?  Are you talking about two different lenses (e.g. an EF-S lens and an EF lens) or the same lens on different bodies?

Under what circumstances do you suppose the SNR would be the same for an APS-C sensor and a FF sensor that each had the same number of pixels?

please read again what Im saying. I do not suppose anything.I describe parameters who must be alike to compare the different sensors, and what kind of qualities the lens for the APS size must have if we are comparing the two sensor sizes and resolution/contrast.
and please  also read The Suedes answer if you wonder something

I have read your comments and the Suede's comments and I find them confusing.  Hence I asked questions in hopes of being enlightened and all I get is defensiveness and avoidance.

[serendipidy]

Well if I can answer with a question. When you look at your picture at 100% on your computer do you think you are looking at the pixels from your sensor ?

Why would you answer with a question?

Socrates used to.

Look where that got him

[Meh]

what is it you are wondering about?
And let me tell you that my english is not the best  in the world, but I try.

For one, I asked you what exactly you meant by "the APS-C lens has to be better than the FF lens"?

I followedd that up with a clarifying question asking if you were talking about two different lenses such as one EF-S lens and one EF lens.

[Sporgon]

Well if I can answer with a question. When you look at your picture at 100% on your computer do you think you are looking at the pixels from your sensor ?

Why would you answer with a question?

Socrates used to.

Socrates gets some leeway.  People who make unclear or unsubstantiated statements aren't generally afforded the luxury of evading questions in that fashion.

I can see where you are coming from in terms of the image projected onto a larger sensor is larger. This is where the potential improvements in IQ come from, and I suppose is the basis of this whole thread. An image that is recorded at a larger level has the potential to record more detail given the limitation of lenses and pixels. This is where Mikael is coming from. It's simple physics. However it is wrong to believe that the data from a smaller sensor has to be "enlarged" or "blown up" more than a larger one of equal digital capacity. The image you will see in pixels created by your computer program is the same size from an 18MP 7D as it is from an 18MP 1DX. The pixels created by your computer program, using the information recorded by the camera chip, are the same size for each camera, irrespective of how big or small the original pixels were on the chip.

I have understood from your previous posts that you believe that in order to achieve a digital picture of a given size you have to enlarge each pixel from your sensor until you have the image size you require. 

That's plain wrong - there's nothing to substantiate !

 

[al-toidz photography]

You guys are wasting your time with this pixel peeping bullshit and sensor S___ that you guys are talking about. First, not because you have a full frame sensor does not mean that you can produce a better picture than someone that has APSC size sensor. Second, lens matters. Even if you have full frame camera but has only a mediocre lens in front of the sensor, the resulting image is not as good as let's say, a T2i with 85mm 1.2L or a 70-200 IS II. And lastly, if you are really a good photographer if not great, then any of this camera and lens S___, will mean nothing to you. What do I mean by this? There's a lot of ingredients that involves in photography more than just a camera and a lens. One does not make a good photo just because he/she has the top of the line camera and lens.

[Plainsman]

If you can get close enough to your subject with a 36x24 sensor camera to fill the viewfinder then FF camera is to be preferred. If the image is small in frame with lots of cropping eg aircraft in flight or BIF then the APS-C format is just as good. There are other considerations of course such as pixel size, lens quality etc etc.

In film days the bigger the format the better eg my Mamiya 645 (56x42mm neg size) always beat Nikon/Canon SLR (36x24mm neg size) - for quality large prints - and a Pentax 6x7 (70x56mm neg size) would always beat a Mamiya 645 etc  The same analogy applies to digital.

I suspect that in the long term the APS-C format may disappear - but maybe not!

[AlanF]

There is a famous old New Yorker cartoon with one professor saying to another: "The reason why university politics is so bitter is because the stakes are so small.". Substitute 'photographer' for professor and 'FF vs crop debate' for university politics................