Are some of your lenses outresolving your sensor?

[bobatkins]

<p>People are confusing resolution and MTF here.</p>

<p>There's absolutely no doubt whatsoever (despite what you might read on the web), that current Canon (and Nikon and probably Pentax, Olympus and Sony) lenses are capable of far higher resolution than any DSLR sensor. Not just a bit higher, but WAY higher. From my testing I'd say at least from 2x to 3x higher when the lens is operating at it's best aperture and you're looking at the central region of the frame (not the corners).</p>

<p>What people are really taking about is the resultant MTF of the sensor + antialiasing filter + lens at or near the resolution limit of the sensor. This has little to do with lens resolution per se, but quite a lot to do with the lens MTF in the, say, 50-100 lp/mm region. That's not technically resolution. It's more closely related to contrast.</p>

<p>The "lack of bite" seen by some pixel peepers is mainly related to the nature of the anti-aliasing filter, but without it you'd by troubled by things which would look worse than an image with less than optimum "bite" when looked at at 100% on a monitor screen, such as "jaggies" on diagonals and moire patterns.</p>

<p>What some my miss is that the better lenses get and the better sensors get, the better technique you need to get those ultra-sharp images. If you look back to the days of film when people were trying to get 100 lp/mm+ on film, you'll see that they had to use a tripod, mirror lock up and sometimes focus bracketing to get it. Take a hand held IS lens, autofocus and try to duplicate that and it's very likely that you'll fail. I suspect that both the sensor and the camera are outresolving the photographer in a lot of cases.</p>

[alan_rockwood]

<p>Many years ago one of the photo magazines (I think it was Modern Photography, but it might have been Popular Photography) did a test on several 50mm lenses and demonstrated on-film resolution of 100 lines/mm. (Not all lenses reached this on-film resolution, but some did, and several others came very very close.)</p>

<p>According to the Nyquist sampling theorem, a digital sensor would need to have at least 200 sensors/mm to resolve 100 lines/mm. You would need 34.56 million true pixels on a 24mmx36mm sensor to achieve this. As far as I know there are no "35mm" digital cameras that achieve this. Therefore, there are lenses today that outresolve the sensor. (I will not deal with reduced-size sensors in this post.)</p>

<p>Also, note that 35 megapixel Bayer sensor is not a true 35 megapixel sensor owing to the interdigitation of the sensor elements for the different colors, but now that I have opened that can of worms let me not discuss it further in this post.</p>

[yog_sothoth]

<p>Lenses are good in the middle, but at the edges and corners at wide apertures the lenses can get prety funky.</p>

<p>Also, contrast and distortion are important as well.</p>

[jamie_robertson2]

<p>John A,</p>

<p><em>"Jamie, I don't get this statement. The reason one uses 8x10 versus 35mm has nothing to do with the fact that the lenses are better or can resolve even to the level of what film can capture. It is about real estate. LF lenses have lower optical resolution than 35mm lenses, but when you start talking about using a 240mm lens to capture what a 35mm camera might need a 30mm lens to capture, you are talking magnification--less resolution to get more detail because that detail is bigger."</em><br /><em></em><br />John, I didn't say (and nor was I insinuating) that LF lenses are superior. I was simply saying that the sheer detail that can be captured on a 10x8" LF transparency is incredible (still far superior to any digital camera to date). And all that detail is created by light coming through a single lens. If, as some people here are saying, that today's sensors are starting to outresolve lenses then how do you explain the detail captured on a 10x8" LF transparency? Especially considering that you say LF lenses have lower optical resolution than 35mm lenses.</p>

<p><em>"Shoot a Canon 1dsmkIII or 5dII with the best glass you can find, it is not tack sharp at 100%."</em><br /><em></em><br />I have the 5dII and that statement is simply not true! However, I do agree that many shots are not tack sharp at 100% but I am absolutely positive that this is down to minor movements in focus and is nothing to do with the resolving power of the lenses. If what you are saying is true then <strong>EVERY</strong> photo taken with a 5dII will not be tack sharp at 100%. That is not the case. If focussed accurately, <strong>EVERY </strong>photo is indeed tack sharp at 100%.</p>

<p>Think about it, we've all used 8MP or 10MP DSLRs and have found that all of them can produce tack sharp images at 100%. But not all of the photos taken with these low MP DSLRs will have been perfectly focussed. They will be 99.9% in focus but not all of them will have been absolutely bang on the mark. However, this is never noticed because these 8MP and 10MP sensors simply can't bring in the detail necessary to home in on these minor issues like today's 20+MP DSLRs can.</p>

<p>Take a look at most shots from a 5dII at 100% and although the intended point of focus (someone's eye on a portrait photo for example) may not be tack sharp at 100%, there will almost always be an area of the photo that <strong>IS</strong> tack sharp at 100%. This proves that it is a focussing issue rather than a resolving issue.</p>

<p>To further illustrate this point, here's a shot I took with my own 5dII. I agree that the photo itself is fairly poor but take a look at the detail. The first image is the full photo of the bird reduced to 10% of it's original size. The second image is a crop from the same photo at 100% magnification. These images have not been messed around with. The 5dII DOES produce tack sharp images at 100%... if you nail the focus! In my opinion, Canon needs to work on it's AF rather than its lenses.</p>

<p>Pixel peepers need to forget about resolving power and should practice using their equipment correctly. Rattling off shots on a 5dII like you used to do blast off a roll of 35mm film will not give you tack sharp shots all the time. You need to take your time, use a tripod when you normally wouldn't and spend more time getting the focus correct. As Bob Atkins says: <em>"What some may miss is that the better lenses get and the better sensors get, the better technique you need to get those ultra-sharp images." </em>Of course, this only applies if you consistently pixel peep at 100% magnification.</p>

<p><img src="http://www.lanticocean.co.uk/misc/image.jpg" alt="" /><br /><img src="http://www.lanticocean.co.uk/misc/100.jpg" alt="" /></p>

[Tim_Lookingbill]

<p>Wow! That's incredible, Jamie.</p>

<p>That's the most detailed and sharpest looking digital capture at 300mm I've ever seen.</p>

[oskar_ojala]

<p>What Bob said.<br>

Although ideally a camera would have a matched lens that offers 100% MTF up to the Nyquist limit and then drops sharply off to 0, so no AA filter would be necessary. However this is practically impossibly to do and not very practical since the sensor will most likely be obsoleted in a few years time. But I wanted to bring this up since in practice the MTF of the system itself plays a key role for the the image quality, not so much the maximum resolving power of the lens.</p>

[jamie_robertson2]

<p><em>"Wow! That's incredible, Jamie.</em><br /><em>That's the most detailed and sharpest looking digital capture at 300mm I've ever seen."</em><br /><em></em><br />Thanks Tim. Unfortunately not all shots from the 5dII are like this. Even taking your time and lining up the AF point does not always guarantee a tack sharp shot. The very slightest movement in focus, especially at wide aperture, results in an image that cannot truly be described as tack sharp. This is due to a combination of the 5dII's AF system and also the incredible amount of detail that the camera captures. Of course, almost all shots look pin sharp when printed large (A3 size for example) but if you're a pixel peeper you will see that many images from the 5D2 are not tack sharp. In the real world this doesn't actually matter much unless you produce monster sized prints regularly.</p>

<p>Having said all this, the 5dII is still my first choice out of ANY camera currently available. That includes the D3x, 1DsIII and all MF digital. The 5dII has the perfect blend of reasonable performance, compactness, portability and image quality with the back up of the broadest range of lenses and accessories. I also like the HD video capability which, although functionally limited, produces stunning video.</p>