[swanlefitte]

is it then reasonable to assume that full frame and APS-C sensors (or any two sensors of different sizes) with the same pixel density should be capable of resolving the same level of detail?

Like a k1 and a k1 in crop mode? But if the pixel density is the same the smaller sensor has less pixels.

[Wheatfield]

But when the optical instruments are more evenly matched, what then?

Then more real estate = a better image.

The sensor is key, clearly. What if the optical instruments are outstanding on both, but the full frame sensor is an older 12MP model, whilst the APS-C sensor is five years newer and 24MP, with greater resolving capability, dynamic range and high ISO performance? That's unfair, of course - as extreme as your lens example - but I'm using it to emphasise the need to qualify the statement that "greater sensor real estate equates to better image quality". What about two sensors from the same era... Even if technical data suggest the larger sensor is better than the smaller, does it translate to appreciably better image quality? Possibly (probably, perhaps)... but under what scenarios is that benefit realised, and to what extent? Will the "average" user (if there is such a thing) realise those benefits? Will the person asking "will I get better image quality from a K-1 than a KP" realise those benefits?

It doesn't matter if the benefits are realized or not. Taken to the lowest common denominator,m there isn't much difference between a cell phone and a full frame or larger DSLR. The larger format still gives a superior result. It's there if you care to look.

Since I started the thread, that person is me... and I'd hope you know I'm always honest I'm happy to start off with format being the only significant difference in the comparison. But we should recognise that opinions and advice given to others in these (and other) forums regarding larger vs smaller sensor formats is usually related to practical usage - for instance, where folks are deciding which camera and lens to buy... and then, factors other than sensor format really do matter, and blanket statements become riskier. If a person is going to give an honest recommendation on comparative image quality between sensor formats when asked for advice, these factors have to be considered... IMHO.

If the only significant difference is the sensor size, then the larger sensor wins out every single time.

[VSTAR]

I think the 'more real estate' argument is something that was very definitely true in the film era, but is a lot less true in the digital age.

….But here's the thing: in digital photography we are almost never looking at an enlargement. .

Not sure about everyone else.....but I still print my favorite prints...and occasionally print poster size. No question at that size there are differences in the prints depending on camera used, sensor size, and lens used. You are correct that on an average computer monitor, unless you are pixel peeping, a low resolution image may look fine....but then I did not purchase a K1 for that purpose.

Sort of like automobiles....they all get you from a to b...but they all drive differently.

Hey...hasn't this site discussed this topic already several times in the past...or am I having deja vu???

[beholder3]

Not necessarily. The amount of light can be limited by the lens aperture because of the depth of field required for a shot. The amount of light can be limited by the exposure time is something is moving in the scene and we want to have it sharp, and this exposure time doesn't depend on the lens, or sensor size. You know that.

Neither DoF requirements nor the potential to extend exposure times are variables in the most often used comparison scenarios. If they were then sensor size would be even less relevant than it is anyways. A smartphone sensor on a tripod at base ISO can already produce extremely high technical image quality aspects.

[Rondec]

Smaller sensors have gotten very good. They do well up to iso 3200 for sure, with cameras like the KP. The biggest negative with cameras like that are that dynamic range really goes down with increasing iso, even though noise is well controlled. I would say further that for the majority of photographers they are good enough.

The thing is that if you are shooting of camera jpegs or doing minimal image processing to your RAW images, then you probably don't care if your camera has an extra EV of dynamic range in the shadows.

Additionally, as has been mentioned, the lens you are using plays a huge factor in your end results. It is easy to say "assuming lens on both formats out resolves the sensor," but the reality is that in many cases the lens doesn't. Even high quality lenses like the FA limiteds, need to be stopped down to get good edge sharpness on a K-1 and I have not been able to good edge sharpness at all with my copy of the 18-55 on the K3 at any aperture.

Overall, my experience with a 24 megapixel APS-C camera is that it is significantly harder to pixel level sharpness as compared to cameras that don't have that level of pixel density. You can do it, but you need decent shutter speed (or sturdy tripod) and a sharp lens or it isn't going to happen.

In the end sensor size is about compromises. Cameras with larger sensor do tend to cost more (although their price has come down) and require larger and more expensive lenses. Obviously, this is true, not just in terms of full frame versus micro four thirds/APS-C, but also medium format versus full frame. We choose a camera that fits our budget and needs best. Fortunately, all the cameras on the market are pretty capable at this point and sensor size doesn't tend to be the limiting issue.

[Zooland]

Not sure about everyone else.....but I still print my favorite prints...and occasionally print poster size. No question at that size there are differences in the prints depending on camera used, sensor size, and lens used. You are correct that on an average computer monitor, unless you are pixel peeping, a low resolution image may look fine....but then I did not purchase a K1 for that purpose.

Sort of like automobiles....they all get you from a to b...but they all drive differently.

?

You can’t drive a Lamborghini with flat tyres.

[biz-engineer]

Neither DoF requirements nor the potential to extend exposure times are variables in the most often used comparison scenarios. If they were then sensor size would be even less relevant than it is anyways. A smartphone sensor on a tripod at base ISO can already produce extremely high technical image quality aspects.

What you write is right, but it wasn't what I wanted to point out.

Let's take an example. Imagine I want to photograph people standing on their feet, they may be moving a bit, and so I want to use a shutter speed of 1/50th s., regardless the sensor size. In that case, I could use a medium format camera and stop down the lens to maintain the same DoF, but if I stop down the lens I now have to increase my ISO, which negate some of the benefit of the larger MF sensor.


My point is, there are constrains of DoF and shutter speeds in actual shooting situations, and those constrains will prevent to reach equivalency of formats, no matter how good is the lens you use.

[victormeldrew]

Putting aside SNR, a 24 MPix FF sensor would match a 24MP APS-C sensor on both print and pixel peeper level when attempting to create similar images of the same scene. But the FF sensor would tend to have a better SNR which means it would out-resolve the APS-C sensor for scenes involving high ISO, shadow recovery, and very low contrast details.

Putting aside the engine, a Ferrari would match a Honda for speed. Since SNR is the biggest benefit of greater pixel size, putting it aside is meaningless.


SNR does not just affect those scenarios, but all scenarios. For very small pixel pitches, a good exposure will involve counting a small number of photons. That means that quantum granularity becomes very real. A handful of photons either way (due to noise, or chaos) will make a significant difference to the measured light level, whereas on a large pixel they would be overwhelmed by the true signal. This means greater fidelity at all light levels and ISOs. It has a similar effect to bit depth in this regard. Yes, it is more noticeable when raising the noise floor, but not exclusive to it.

[biz-engineer]

Putting aside the engine, a Ferrari would match a Honda for speed.

Not necessarily, when driving downhill, the heavier car would go faster, without the engine

I think we're actually saying the same thing even though you sound like you're disagreeing. If you keep FoV, DoF and shutter speed the same (so all exposure params except ISO), then the larger format will have a dimmer image because the light is spread over a wider area and you must compensate by increasing ISO/gain. If you can increase the light intensity recorded somehow so you can run the sensor at ISO100 again then you're recording more light, so you get a better SNR of course! If you took the same larger format and tried to condense it onto a smaller area, you'd find now that you're already at base ISO and you blow the highlights.

So, yes, we both agree that IFF you can run the sensors both at base ISO, then the larger one will do better. I carry it one step further to try to argue that for an equiv image, above base ISO you'll have to be at a higher ISO on the larger sensor by exactly the difference in sensor size, so there's no benefit anymore in terms of noise.

If that's true, it'd be the best explanation for why writers perceive that image quality suffers when using lenses designed for full-frame cameras are used with APS-C sensors. I'm not sure it is true. There's two things that affect perception of image quality that I don't think have been considered.

First, everybody's eyeballs are different. If you think of the retina as the "sensor", then the photoreceptor cells are the "pixels". But there are two basic kinds of photoreceptors, those for color, and those for luminance. And their sizes are very different: color receptors are wider (fewer pixels per square unit of surface area), and luminance receptors are tiny (vastly greater number of pixels per square measure). The thing is that people see things differently because of the variance in the ratio of color to luminance receptors. People with really good color vision see the world as blobs of color (low resolution but very good color discrimination) while others see the world as sharply-defined but washed-out points (very high resolution and light-gathering ability, but low ability to discriminate among hues). I fall in the latter category, myself, I have what I call "wolf vision" and other people call "color blindness". I can see in what other people think is total cave darkness, and "image quality" to me is the ability to resolve fine detail regardless of color. So there are two aspects that are important to me, sheer number of pixels, and the size of each pixel. If it takes four pixels on a KP's sensor to do the same thing as one pixel on a K-1's sensor, then the KP has greater image quality (with respect to that one area) because there will be fine differences in luminance among its four pixels, which will all be averaged together in the K-1's one pixel. The K-1 more than makes up for it, however, by having a larger number of pixels overall. When the resultant images are compared in an proportionally-resized format, the KP's picture will be smaller than that of the K-1, but the image quality will be better; when resized so that both are the same size, the K-1 will have the better image quality.

The second thing I'm thinking is that we fail to recognize that the light arriving at the sensor is not digital. It is, for all practical purposes, continuously varying. Whether the light hitting a given point on the sensor is brighter or dimmer (because of the kind of lens used) has more to do with the ISO setting than anything else. But the way they adjust sensitivity appears to me to be the result of ganging pixels together (groups being used in effect as a single pixel) in order to add the light captured together, analogous to the use of larger silver salt crystals in the emulsion to achieve greater sensitivity. "Noise" isn't because of stray light hitting the over-sensitized pixels, it's the loss of resolution due to increased granularity, which is why the use of the "Gaussian blur" function can make the picture look better by creation of new pixels between the pre-existing pixels by interpolation, in effect "resizing" the pixels themselves.

People with better color vision can tolerate less fine an ability to resolve detail in images while those tending toward color blindness will be more tolerant of inability to detect contrast among adjacent hues. Both kinds of contrast information (variations in luminance and variance in color) are important to image quality, but everyone will see that differently.

[clackers]

Not necessarily, when driving downhill, the heavier car would go faster, without the engine

C'mon, Biz, you remember your physics - no difference in the fall rate of heavy or light objects.

[AstroDave]

Not necessarily, when driving downhill, the heavier car would go faster, without the engine

Depends on friction! If no friction, everything falls (= goes down hill) at the same rate, regardless of weight (mass). Galileo, about 1600!

(Clackers beat me to it!)

[SSGGeezer]

I only have 2 days with my K-1 but using the same lens, I can see the difference over my KP. And on several shots I had to pull some deep shadows and the results pleased me.

[AstroDave]

But the way they adjust sensitivity appears to me to be the result of ganging pixels together (groups being used in effect as a single pixel) in order to add the light captured together,

NO!!!!!!!!!!!

It is the gain of the amplifier which gets the electronic charge from each pixel which is varied, before the analog-to-digital converter which produces the digital light level values.

From: Sensor sensitivity (ISO) in digital cameras :

ISO settings have a direct influence on the amplifier before the analogue-to-digital converter (ADC): high ISO numbers give more amplification, while low ISO numbers give less amplification. The camera sensor itself always maintains the same degree of sensitivity; only the level of amplification changes. Depending on lighting conditions, the ISO setting will either be selected automatically by the camera or can be changed manually.

[biz-engineer]

Depends on friction! If no friction, everything falls (= goes down hill) at the same rate, regardless of weight (mass). Galileo, about 1600!

Friction and weight are two independent variables. On a race bike, I can guarantee that the heavier goes downhill faster.