[Tony Belding]

When you are shooting film, there's a big difference in image quality between a 110 pocket camera, 35mm SLR, and medium or large format. Film grain size is a limiting factor (especially with color negative film), and going to a larger piece of film gives you much-needed improvement of clarity and resolving power.

With digital sensors this element still exists, with larger sensors typically (not always!) providing higher resolution output, but its importance has been greatly reduced. I can take very clear photos at 12 MP with my Q7, and that's plenty of detail and clarity at any sizes that these photos would normally be printed or displayed. Going to higher resolution sensors gives us some additional leeway for cropping in, or for making very large prints, but that's all. It's not like film where the difference would be obvious in every photo.

Larger sensors also provide a better signal-to-noise ratio, or dynamic range, which means that higher-ISO images taken in low light will look cleaner. When you were shooting film, higher-ISO (or ASA speed!) film was grainy, it was gritty, and shooting much of anything indoors without flash was an iffy proposition. Digital images also get gritty when you crank up the ISO gain, but we've reached the point now where sensors are so good, this again has become something of an edge case. You can now shoot digital cameras, FF or APS-C (or even M4/3!), in remarkably low light and still get very usable images. FF has an advantage, but in actual practice both formats are very good, and the difference between them isn't that much.

And that leaves us with one FF advantage that technology hasn't changed, which is the "bokeh" factor. It's simple laws of optics that say if you want a shallow focal depth, blurred background and subject isolation, it's going to be easier with a longer focal length lens, and that's going to be more practical on a larger sensor. This is a big part of the "medium format look" that some people chase after. However, if we are realistic about this, blurring the background is just a visual effect. It's not a measurement of image quality, and it's not an effect that benefits every photo or arguably even the majority of photos. Traditionally it's an effect that has been sought for portraiture, and if you take a lot of portraits then maybe you care a lot about this, and if you don't take many portraits maybe you don't care at all. Meanwhile, it's easier to get telephoto reach out of small sensors, so if you are a wildlife or sports photographer you may think M4/3 just beats FF all hollow.


To sum it all up, in my opinion, the difference in "quality" between APS-C and FF is minimal and doesn't make much showing under typical shooting conditions.

[mlaird]

Since I have only played with a K-1 in the store, it was interesting to see how you could actually describe the differences between a 16Mp K-5 and a K-1 in crop mode.

I've been wondering the same thing. I have a K5 and like it a lot, but am torn wondering about whether to upgrade to the K1 or wait for the next APS-C flagship model. If the K1 produces the same quality or better when shot in crop mode as compared to my K5, I wouldn't have to worry about the loss of telephoto range by going to full-frame.

[pschlute]

If the K1 produces the same quality or better when shot in crop mode as compared to my K5, I wouldn't have to worry about the loss of telephoto range by going to full-frame.

Both will produce a 16MP image. Technology advances between the K5 and K1 should give the K1 the edge, but i doubt anyone could tell the difference for normal web viewing.

As far as "losing" telephoto range by moving to FF, you won't. A lens produces the same magnification at the sensor whatever format it is mounted on. A FF sensor captures a wider field of view, not a less magnified image. Cropping the FF image in PP or using the K1 crop mode will yield the same image as the K5.

What will make a difference is the pixel density of the sensor. So a K3/KP (24MP) for example has a higher pixel density than the K5/K1. This will mean you can crop the image more without pixellation. If at some future date Pentax releases a much higher MP FF camera that has for example 30MP in crop mode, you can say that your telephoto has "more reach" on that camera than on the K5/KP

[Mikesul]

These "quality" discussions are interesting, often informative but in the end perhaps futile. There are always technical data which is precise and accurate but most of the time we see that those differences shown by the data do not yield visibly different results. Perhaps rather than speak in imprecise terms like better, or quality we should just look at the data and then look at the result people with skills similar to our own get with the equipment. I often look at older photos and cannot tell which camera I used without the EXIF data. Q7 surprises me all the time!