Understanding lens resolution

Discussion in 'Canon EOS' started by bob_estremera, Sep 2, 2011.

  1. While working my way toward deciding on a 60D (love the flipout LCD) versus 5DMK2 as an upgrade to my 450D, I have been researching lens resolutions and getting a bit confused.
    Making prints up to 20X30 is one objective. And I've already read every post of that 28 page thread comparing 7D to MK2 for large prints so no need to rehash that here.
    Thinking that print quality is highly dependent on the glass, I thought that if I decided on the 60D, I should at least pair it with 'L' lenses in the event I ever make the jump to FF. And if I don't, I still have Canon's presumably best lenses.
    Using photozone for test data, I checked out the 17-40 and found something I don't understand that I'm sure has to do with testing on FF versus cropped.
    The 17-40 resolves 2443 lines at 5.6 on a 50D. On the 5DMK2, it resolves 3422 lines.
    Even my kit lens 18-55 resolves around 2400 lines at 5.6 as does the more expensive EF-S 15-85.
    Two questions:
    1. Is it true that the 17-40 does not provide more resolution of sharpness than the EF-S lenses, including my kit?
    2. Why are the resolution figures so different when tested on FF versus cropped?
    I'm hoping this thread might be invaluable information for lots of photogs besides me.
    Thanks, Bob
     
  2. Print quality is highly dependent on many factors, the quality of the glass being only one of them (and certainly not the most important for all prints).
     
  3. Forget resolution, get a camera and use it. Hand holding limits your resolution tremendously, contrast, exposure, subject matter, EV etc etc are all big factors. I don't understand your resolving lines figures either, lines per what? Inch, mm, sensor?
    Detailed 20"x30" prints from a crop camera are, depending on your personal opinion of acceptable, unrealistic, unless you limit viewing distance.
     
  4. Nose-to-glass on a 20x30 print is an unrealistic viewing distance.
     
  5. True, as is expecting people to stay ten feet away.
     
  6. What Rob and Scott say is absolutely to the point.
    As for
    2. Why are the resolution figures so different when tested on FF versus cropped?​
    the answer is that different parts of the total image cast by the lens are being measured. APS-C (it's its own thing, not a 'cropped' anything) images measure only the middle 22.3 x 14.9 mm of the image on Canon bodies, while the 35mm-sensor (apx. 24x36mm) covers more of the edges of the lens field.
    The old idea was that the APS-C (aka DX) format used the better central portion of the field, the so-called "sweet spot"; but many tests of modern lenses suggest that this is not a universal principle.
    In any case, lenses are often not as good out to the edges as they are in more central portions of the image.
    (A classic example of the differences can be found in the little EF 50mm f/1.8 lens, which is wonderful on a APS-C body, but more "how good for what it costs" on a 35mm-sensor.)
     
  7. If you read the Photozone test you will see a little chart that shows the camera resolution limits - their 50D chart shows 2700 while the 5DII chart shows 3700 (I looked at the 85 F1.8 charts). This resolution difference is just full frame vs APS-C plus the 15 Mp vs 22 Mp sensor (the 7D / 60D will resolve more). What you may want to look at is the resolution shots on the digital picture as they tend to show you more what you can see. However, the choice of lens should not be confined to resolution. The factors to consider are edge vs center resolution, the difference in performance between a high contrast and a low contrast subject (good lenses perform well on both), colour and contrast, CA distortions and vignetting. You will also notice that stopped down the differences between a great lens and a reasonable lens (in resolution terms) start to disappear. You pay a lot for wide open edge performance - this is why some people shoot the Nikon 14-24 F2.8 on a Canon as it is a better lens than my 16-35 II.
    I have owned the 17-40 and it is a good lens but a bit soft at the edges. A quick look at the digital picture shows the 17-40 (at 17mm and F4) is sharper in the center but softer at the edges than the 17-85. Having owned the 17-40 I found the other factors (colour, contrast etc...) of this lens were very good and to me this "drawing" style is important. The 17-40 is also weatherproof and will work on full frame. The APS-C lens people rave about (I have not used it) is the 17-55 F2.8. As Scott says just take photos - over time you will decide what you like in a lens. Personally my favourite lenses are my Leica and Contax rangefinder lenses and my Fuji Medium Format lenses as they all have a "German style" which tends to be more balanced and less about high contrast center resolution. Bob Atkins has written a number of great articles on resolution - perhaps this may be of interest
    http://www.bobatkins.com/photography/digital/canon_eos_7D_review_4.html
    The Digital picture crops are at
    http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=251&Sample=0&FLI=0&API=0&LensComp=100&CameraComp=474&SampleComp=0&FLIComp=0&APIComp=0
     
  8. Scott: Lines, from photozone: "line widths per picture height (LW/PH) which can be taken as a measure for sharpness"
    I assumed photozone's testing criteria was something universally accepted but this might not be the case.
    JDM, I used the word 'cropped' only as it is used to denote APS-C sensor.
    I'm just trying to understand the technical side of how lenses are evaluated for sharpness. I know that absolute critical sharpness is often NOT the measure of a 'successful' photograph but I want at least to learn how to approach lens choices with more, not less knowledge.
     
  9. Rob,
    From my 5D I have a photo of the Taj that can bear Nose to glass viewing on the 20x30 print on my wall.
    I actually suggest firends to look that closely to see the beautiful detail on the Taj that they can see on the photo and then go back and enjoy the view as well.
    20x30 to me is the ideal size for both details and far view at the same time. From a feet away it fills your field of vision transporting you into that location and at the same time the detail if there would allow you to see it well.
    BTW for me anything that is around 12 inches is the nose to glass viewing distance as that is the distance at which our visual acuity is the most - human perceptual resolution is maximum.
     
  10. Bob - you need to understand resolution tests - they are performed across the lens using line pairs of varying contrast. In essence you have line pairs of different reflectance that will give a different contrast (e.g. a line of 75% reflectance then one of 25% reflectance is a 50% contrast). The test measures the ability of a lens to resolve at various contrast levels and various line spacings. Most tests now display an MTF charts - this plots contast on the vertical axis - 1 = 100% and (usually) distance across the bottom the numbers are distance in mm from the center of the frame - thus 20 is 20mm from the center of a 35mm frame. In general the plot shows a series of thick and thin lines thick is 10 line pairs per mm, thin is 30 lp/mm. The blue lines (in Canon's case) are at F8 and the black wide open. The solid and dashed lines are S and M (Sagital and Meridonial). From a layman's point of view you can regard these as evaluating the Bokeh of the lens - the closere the solid and dashed lines the more pleasing the Bokeh
    Here is a canon MTF chart
    http://usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ef_17_40mm_f_4l_usm
     
  11. I used the word 'cropped' only as it is used to denote APS-C sensor.​
    Yes, I know. And I am saying what I did because this sort of usage too often leads to value judgments about "upgrading" to "full-frame". I am happy that you said "jump" not "upgrade."
    APS-C and 35mm (Nikon does it better with "DX" and "FX") are just different formats.
    Although some medium-format fanboys will speak of "upgrading" to medium format, most of us recognize that this is not an "upgrade" but simply a change, like moving from medium format to the ultimate "upgrade" -- to wit, 8x10" view camera.
     
  12. My photography is about taking pictures of cameras and lenses. My best work is photos of MTF charts...
     
  13. Something to think about - and it is very important - when comparing cropped sensor and full frame formats, is the the lp/mm lens resolution values don't tell the whole story. If you put a lens with X lp/mm resolution on a cropped sensor camera and a lens with X lp/mm resolution on a full frame camera...
    ... the photograph made with the full frame camera has the potential to resolve more detail.
    The key issue is what might be described as line pairs per picture height (or width) that result when the lens of X lp/mm is placed on a camera with, as I like to describe it, "more millimeters to hold line pairs." The short story is that the larger format always has the potential to resolve more detail. This was true with film and it continues to be true with digital, and the issue is most certainly not just how many photo sites are on the sensor.
    If you are going to produce very high quality prints at the 20" x 30" size and you will work with detailed subjects in which high resolution is a concern and you will work with great care and from the tripod, then the FF format has some advantages for your photography that might make it a better choice.
    Dan
     
  14. Brad, how great for you. You never have to leave the house.
     
  15. My photography is about taking pictures of cameras and lenses. My best work is photos of MTF charts...
    What Brad said, ditto... Modern cameras and pro lenses are so good... yet, they are not sharp enough for your extremely hyper-critical work? Then go work for Canon or Nikkor and get that ''5 more lines per mm'' or whatever.
    I sure don't get it. A 5D2 will take brilliant, sharp detailed 20x30 inch prints. A old 10D can do the same on smaller prints, say 19x13 inches. Sharp and detailed. Use good glass, good capture technique, and proper post processing to print techniques for the best output.
     
  16. The old rule of thumb is that for close inspection you want 300 dots per inch. For 20x30, that comes to 54 megapixels. You need a very expensive medium format digital camera or you need to shoot 6x9 medium format film and scan it at 2400 dpi (which gets you close). I like to goof off with a crown graphic and 4x5 film, which is more than enough for a crisp 20x30 print that stands up to close inspection.
    In reality, most DSLRs with a good lens and good technique can make a very good 20x30 print that will stand up to viewing at a few feet away. A t3i will be up to the task. A 7D will make getting the photo easier.
    It would be interesting to run a double blind test where one shoots the same scene with a 5D II and a 7D and see who can tell which is which from 20x30 prints.
    I have found that a Tokina 11-16 is good enough for 20x30, as is the Tamron 17-50 and the Tokina 50-135.
     
  17. Generally speaking, lenses made for APS-C sensors are sharper than lenses made for FF. So it is not surprising that 18-55 is sharper in the center than the 17-40 4L. But as G.Dan Mitchel explaned, the larger format of FF does not need as sharp lens to resolve a given total number of linepairs as the APS-C format.
    As pixel density increase, the difference in resolution between formats decrease but the larger format will almost always win.
    In the film days, it was a huge difference in resolution between FF (24x36 mm) and MF ( 55x68 mm) when using B&W Tri-X, but not so much when using the fine grain Kodak Tmax 100.
     
  18. Let's get something straight here about my post and what I'm trying to get at:
    I am not a pixel peeper or someone who is driven to care more about 'lines per inch' than in taking compelling photographic artwork.
    But since I am looking into investing in a better sensor camera and better quality lenses, I want to understand what is the criteria on which their performance is based when a quality print is the ultimate goal.
    I am the first to 'get' that resolution charts are not architecture, that megapixels are not portraits.
    Ken, what you said, I have read before. That modern lenses are so good now that with proper capture, PP and printing, they are all pretty indistinguishable from one another and one is better off not obsessing over them and just go out and shoot.
    And if that's 'one' of the truths learned from this post, that's all I'm looking for. And that same knowledge will be helpful to others potentially who happen upon this thread.
    Thanks all.
     
  19. Bob in the real world you tend to notice Bokeh, DOF, contrast, CA and distortion more than resolution in most shots with reasonable lenses. In big prints you will see softness, especially at the edge of the image if you have in focus objects. In general you can stop the lens down to solve the issue - indeed I try to never use my 35 F2 below F2.8 and my 50 F1.4 below F2 for this reason. Even when you do it is usually not fatal - my 16-35 F2.8 II gets pretty soft wide open and towards the 35mm end but people generally do not notice it. Without wishing to re-start a 7D vs 5DII debate (I own them both and they are fine cameras) you can tell the difference on a 20x30 print even at 100 ISO. That said you really have to look hard and unless you have the two side by side would never know. In the real world there is little to choose between them so long as they are at low ISO and correctly exposed - the 7D is a lot less tolerant of exposure errors than the 5DII (I almost always shoot RAW).
    If you plan to shoot at F5.6 then most lenses will work fine so long as the zoom range is not too long (long range zooms are very prone to distortion and CA - on a 35mm camera having a zoom that goes from wide angle to beyond about 70mm causes the lens to have to change from a retrofocus design to a telephoto design which lens designers tell me is where the problems start). The old rule of thumb (which I still go with) is that 3x zoom range is a good cut off.
    If you look at the photozone tests of the 17-40 and the 18-55 kit lens you will see the kit lens has slightly more distortion (3.2% wide and 0.23% long vs 2.47% and 0.08% for the 17-40) but in both cases the distortion at the wide end is noticible although it can be corrected in post processing.
    Vignetting is quite severe on the kit lens (1.4 stops wide open at 18mm) compared to 2/3 of a stop for the 17-40. Again this can be fixed in post processing. In terms of resolution there is little to choose between the two lenses. CA performance from the two lenses is very similar. I have not used the 18-55 Kit lens but I suspect it's Bokeh is not as good as the 17-40 (although the 17-40 is not that great).
    So what are you paying the extra for?
    Well partly the kit lens is much better value due to much higher volumes but also:
    The 17-40 has a much larger image circle so you can use it on full frame
    the 17-40 is much better built and it has internal focusing and will almost certainly be more durable
    the 17-40 has USM focusing so it will have faster AF
    the 17-40 is weather sealed
    the 17-40 is USM so you get manual focusing in AF mode
    the 17-40 comes with a lens hood and soft pouch.
    Is this worth the difference in price - up to you. Buying good glass is a law of diminishing returns although lens hold their value very well. For example my 1988 FD series 85 F1.2 is worth more than I paid new. Similarly my EF 70-200 F2.8 non IS can be sold on ebay for more than I paid for it. This is generally not true of inferior glass which loses value quickly.
     
  20. Bob,
    I understand your quest, but technique will always have a far greater impact on your imaging than almost any lens.
    Testers are almost always inconsistent, those that do have clinical testing procedures are subject to sample variation and technique and tend to be lab-rats. One problem is what are you testing? As you examine testers methodology you start to realise they are almost all testing different things and that testing has gotten so far away from actual real life use as to make the testing almost irrelevant. For instance, one grain of sand on a lens mount can make a huge difference in measured resolution, but that simply will not show in prints or electronic image reproduction. Manual focus is critical in lens testing, but how often are you going to use MF? Some always will but very few. If you AF then all resolution figures are out the window.
    Even the cheapest lens will, technically, out resolve, any sensor, look at the sensor resolution in P&S's, they are over 200 MP if you extrapolate to a FF sensor, but they are not L lenses. But it is how the lens, sensor, AA filter etc all interact.
    To really get to grips with comparisons, you need to think system resolution, not isolate lens resolution.
    "I want to understand what is the criteria on which their performance is based when a quality print is the ultimate goal. " The print is the ultimate measure. The size and viewing distance, the printing technique, the post processing and the capture technique all play major roles.
     
  21. Thanks for further explanations.
    Because I started with a medium format, first C220 then Bronica, I am very comfortable and almost always use a tripod with my 450D. I usually shoot at f8, use base ISO's and the 2 second timer.
    I think this thread has given me the insight I need and can focus on the basic lens selections I need to capture the images that move me.
    Thanks everybody, Bob
     
  22. 1. Is it true that the 17-40 does not provide more resolution of sharpness than the EF-S lenses, including my kit?
    The 17-40L is a good lens, but not necessarily better than the best EF-S and crop lenses. As an example, my Tokina 11-16 f/2.8 is sharper than my Canon 17-40L. This is even more true with the 17-40L on FF.
    2. Why are the resolution figures so different when tested on FF versus cropped?
    Because of the way Photozone presents the results. They explicitly state that you cannot compare results between different sensors, even sensors with the same MP rating. You can only compare lenses on the same identical sensor model. They typically provide a scale next to the results (good, very good, etc.) which lets you roughly compare lenses between sensors.
    Too many people try to read sensor and format differences into their tests. If you want to compare sensors or formats, you need to use tests designed to do that. DPReview and Imaging Resource provide these test results.
     
  23. For the very disciplined and good technique users, there are a couple of lenses that really stand out as killer sharp (if you can call that resolution, probably not, but that is one of the many problems with this kind of thing :) ). The 24 TS-E and the 300 f2.8 IS are both lenses I have used that made me take a breath at how sharp they are. Unbelievably the 50mm f1.4 at f8 is a very, very sharp lens too.
     
  24. Detailed 20"x30" prints from a crop camera are, depending on your personal opinion of acceptable, unrealistic, unless you limit viewing distance.
    They are the same from a 60D as from a 5D mkII. If there are viewing distance limits for one, they will be the same for the other.
    30" is the upper bound for a landscape from either body. Less demanding subject matter or viewing conditions will allow you to enlarge more. A portrait, for example, will scale much larger. At 24-30" the best crop and FF bodies produce very good prints, though there is still room for improvement from future, higher resolution sensors.
     
  25. Right now my Keuffel and Esser slide rule is in Solms getting a CLA. I'll have something important to say on this subject when I get it
    back and can do a few calculations...
     
  26. Stephen Cumblidge - It would be interesting to run a double blind test where one shoots the same scene with a 5D II and a 7D and see who can tell which is which from 20x30 prints.
    Been there, done that. They can't until the ISO goes above 800.
     
  27. "The old rule of thumb is that for close inspection you want 300 dots per inch."
    That rule of thumb turns out to be quite irrelevant for photographic prints. Most printers regard about 180 resolution as pushing the lower limits for acceptable high quality prints.
    I also want to second the comment that things other than lens resolution have a far greater impact on creating photographs that will stand up to large print sizes. I'm not saying the lens resolution is not important, but that many lenses provide more than sufficient resolution for quite large prints, and a whole range of other factors play into the final image quality.
    I differ with some who claim that results from a 18MP cropped sensor camera will be essentially the same as those from a 21MP full frame camera. The 7D can, indeed, produce very fine image quality. However, the fact that larger film/digital formats have the capacity to create greater system resolution is essentially not something worth arguing about.
    On the other side of that statement, unless you work rather carefully, know what you are doing in the post-processing phase, shoot with excellent technique, pay a lot of attention to things like accurate focus and camera stability and then push the upper boundaries of print size and quality... you probably won't see a difference. For example the differences at 12" x 18" prints are very, very subtle and would only be seen by an experienced viewer doing careful side by side comparisons. But somewhere above this size, depending on a bunch of variables, the will be differences.
    On the other, other hand... a camera like the 7D offers some important functional features that you might find more appealing and useful than the increased resolution potential of a full frame camera like the 5D2.
    Dan
     
  28. Many people, even though they are not my friends, praise my brick wall pictures as being my personal best.
     
  29. However, the fact that larger film/digital formats have the capacity to create greater system resolution is essentially not something worth arguing about.
    Theoretical capacity is not the same as realized capacity. If all things were equal a FF sensor would out resolve an APS-C sensor. But it's quite obvious that pixel density is not equal between the 5D mkII and 7D/60D. And pixel density = resolution.
    To put the system difference between the 5D mkII and 7D into perspective, 7D RAW files in ACR yield a higher extinction resolution on a chart test than 5D mkII RAW files in DPP or 5D mkII JPEG files. The difference in total pixels at the sensor is less than the difference introduced by choice of RAW converter. It is also most certainly less than technique, post processing, and lens choices. If you get everything else in the photographic chain right, you are not going to observe a difference in large prints due to the small difference in total pixels on the sensors.
     
  30. Daniel - it depends on what we are interested in. The 7D has higher sensor resolution as it can resolve more line pairs per mm of sensor area (lens issues and diffraction not withstanding). So if I only use 38% of the 5DII sensor area then yes the 7D has higher resolution. But what I care about is the resolution of my image and that is in line pairs per image height and here the 5DII has higher resolution that the 7D. Assuming that you print the image from the entire sensor then the 5DII has higher resolution than the 7D. For more information see numerous sources including Popular photography, Amateur photography, Bob Atkins, dpreview, DXO mark, Photozone etc... In my earlier post I mentioned that on a 20x30 print with the 5DII and 7D image side by side (even at 100 ISO) you can see the difference. However, this really does not matter as the moment you separate the prints so you can no longer directly compare it is no longer obvious. By the way I believe the human eye can resolve around 550 dpi - so clearly there is still benefit in printing above 300 dpi
     
  31. "Extinction resolution" or not, a larger format 21 MP camera is going to have the system capacity to outresolve a 18 MP (or even a 21MP) smaller sensor across the image width. With lenses of equal resolving power, the larger system can "resolve more line pairs."
    To avoid getting into an impassioned argument about "which format is better," let me clarify a few things again:
    1. Both formats can produce finely detailed images when used by a competent photographer.
    2. Unless one works carefully and critically and makes prints that push the upper boundaries of print size, the difference is likely to be quite small and probably not of consequence to most shooters.
    3. There are other factors besides system resolution that would argue for or against either format as the best choice for a particular photographer. For example, the 7D provides some functionality that is not found on the 5D2 that might be more important to some photographers. And some photographers might prefer the wider range of usable apertures (as per limitations due to diffraction blur) of the full frame system.
    It is not necessary nor accurate to claim that a) one type of system is always better than the other or that b) they are equal. They are not equal and the differences can be important - but they can cut both ways.
    Dan
     
  32. Photozone's MTF50 figures are not line pairs per mm but per sensor dimension. The figures for full frame are higher
    because it is a physically larger sensor and also the pixel count is greater in the case of the sensors mentioned. So
    the files are more detailed, as they should be. Now, if you compare a full-frame lens on a crop camera to an ef-s lens
    on the same camera, it is entirely possible that the lens designed for the smaller sensor has an advantage in the
    center. Lenses that cover a larger image area are typically not as sharp as those optimized for the smaller area. Buy
    lenses that work well on the cameras that you intend to use! It's as simple as that.

    I agree that lens tests do not tell the whole story. However I consider "sample variability" a part of the quality of the
    lens and there should be no excuses if the manufacturer allows it in their output. If a review site gets a lemon the
    manufacturer deserves all the bad rap they get as a result. More expensive and simpler lenses typically have less
    variability for obvious reasons (mechanical stability).
     
  33. Thanks for all the input here. Even you Brad. Hope your K&E returns soon. And I'm sure you got very excited when the topic turned to 'extinction resolution'.
    The more I've researched and the more of my own images I look at critically since all of your help, the more I'm leaning toward the 5D with a few good primes that offer even performance across the lens when stopped down. A used 24-70 2.8 can be had for a good price at KEH also.
    When I can finally spring for it, I think I'll have a setup that I can just forget about technical stuff and shoot instinctively with only the image in mind.
    Thanks again everybody. This has been a big help.
    Bob
     
  34. Ikka, your theoretical notion about the optical superiority of the EFS breed of lenses over EF and similar lenses on cropped sensor cameras is not borne out in actual practice. The main reason for producing EFS lenses is not that they are going to be optically better than other lenses.
    This is not to say that there aren't some very fine EFS lenses, including the 17-55 f/2.8, the 10-22, the macro, etc. Others I didn't mention can also be quite credible lenses. But that doesn't mean that the EFS design is going to produce higher resolution than a non-EFS design.
    The "advantage in the center" theory is one that is tossed around a lot without sufficient critical thinking. It is true that resolution falls off, along with light transmission, as we move toward the corners of the frame on any format, and that the farther from the center we have to go the more the resolution might decline. But this ignores several important things:
    • The FF system starts out with higher center resolution of the camera/lens system by comparison to the center resolution of the cropped sensor system.
    • Even at the edge of an APS-C sized section of the FF sensor, the overall resolution in lp/frame width terms is still higher.
    • It continues to be higher beyond this point. On some lenses, and at some apertures, it remains higher all the way to the corners, while on others the situation might be different.
    In a worst case - a pretty bad lens on a FF body - it might be possible for the resulting image to have noticeably diminished corner resolution at the largest aperture in a very large print. In more common cases, and especially when shooting at more typical apertures, the corner performance on the FF system will be as good and more likely better than that of the smaller sensor system.
    Disclaimer: I'm not saying that full frame is necessarily "better" than crop - there are other factors that can make this stuff unimportant and other factors more important for individual photographers. But the arguments that smaller sensor systems will equal (or even exceed!) the resolution capabilities of larger sensor systems are specious.
    Dan
     
  35. +1 with Ken and Brad.
    It a workflow issue, and expectations. Whether your are deliberate from the onset, or find yourself in a moment that you would expect to hit a decent 20x30 print. Then good technique, movement in the scene, enough lighting to keep at lowest ISO to have motion stopping shutter speed, etc. That's only half of it. We now have software and printing tools that extract a great deal of data, and create more perceived sharpness, even from what was otherwise junk antique lenses from the film days.
    I look at my old film shots, from decent FD lenses, and I now have a second opinion when compared to my digital. Yes, those old 35mm prints are sharp, but only sharp as can be from the tools we had to deal with back then.
    Granted, it's hard for some folks to understand just exactly what is possible now, when they have nothing to compare to how it was even ten years ago. Fortunately, many of our clients are not so well versed. I've sold many prints at 24" to customers whom never considered it was shot with a 40d and a kit lens.
    Life is so much easier when you simply let this stuff go, and judge an image for how cool it looks.
     
  36. Ikka, your theoretical notion about the optical superiority of the EFS breed of lenses over EF and similar lenses on cropped sensor cameras is not borne out in actual practice.
    I didn't say that EF-S lenses are optically superior. But the designer has an advantage if they only need to cover a small area they can make the lens superior in that area, if they choose to. Whether this actually happens with actual commercial lenses is another matter and product positioning and marketing play a key role here. Canon doesn't want to market high end EF-S lenses because they want the more expensive lenses to be always better even if they have to fight physics to get there. It would be much easier to make slow lenses better quality than fast lenses, for example, if marketing didn't decide that the more expensive lens has to be better quality to avoid confusing customers. This is a great pity. (The 70-200/4 is one exception to the general practice followed by most manufacturers.)
     
  37. Philip - Daniel - it depends on what we are interested in. The 7D has higher sensor resolution as it can resolve more line pairs per mm of sensor area (lens issues and diffraction not withstanding). So if I only use 38% of the 5DII sensor area then yes the 7D has higher resolution. But what I care about is the resolution of my image and that is in line pairs per image height and here the 5DII has higher resolution that the 7D.
    I'm not talking about cropping a 5D mkII image to give the same FoV as on a 7D. I'm talking about just the sensors. The 5D mkII has a 21 MP sensor and the 7D has an 18 MP sensor. And that 3 MP difference, at the end of the photographic chain, amounts to less than one's choice of RAW converter. (See DPReview's chart tests.)
    I'm not going to get into the print debate again. Suffice it to say that I've never had anyone tell me which came from which, either with large prints or with 100% crops presented repeatedly in this very forum. If somebody could readily tell you which print came from which, then you probably did not sharpen the 7D file appropriately. (Amateur Photographer UK came to the same exact conclusion, btw.)
    By the way I believe the human eye can resolve around 550 dpi - so clearly there is still benefit in printing above 300 dpi
    As with everything else, the human eye's ability to resolve detail depends on detail contrast. Given B&W line art the human eye can resolve detail well past 1200 dpi. Given average color photographic detail, you've hit the limit at around 250 ppi. (Note I said average. A silhouette for example, having higher contrast, might benefit from higher printing resolution. I can recall one print test I performed with a few friends using MF drum scans. The color detail was done by 250 ppi, but the model's black hair against the white backdrop saw improvement to around 500-600 ppi.)
     
  38. a larger format 21 MP camera is going to have the system capacity to outresolve a 18 MP (or even a 21MP) smaller sensor across the image width. With lenses of equal resolving power, the larger system can "resolve more line pairs."
    Only at the extinction resolution of the lens (MTF10). But sensors are no where near that pixel density.
    Out of camera a 21 MP FF sensor will yield a higher MTF50 lpmm result than a 21 MP crop sensor, all other things being equal. The average photographer would not describe this as "higher resolution" but as "greater sharpness" because the same detail is present in the crop file, just at a lower contrast (i.e. MTF40). The trick is that they are so close, because the formats are so close in size, that simply sharpening the crop output will yield the same MTF50 result. This is pretty much true for sensors within a certain MP range of each other as well.
    Which brings us back to this: your choice between Canon's 21 MP FF sensor and their 18 MP crop sensor is less important than: technique; lens; RAW converter; post processing skill; printer; paper choice. At the end of the photographic chain it's non-observable. It's hardly observable when you isolate everything else and look for it in a chart test.
    Unless one works carefully and critically and makes prints that push the upper boundaries of print size, the difference is likely to be quite small and probably not of consequence to most shooters.
    They're quite small and not of consequence even when you work this way.
     
  39. Ilkka is correct regarding lenses. It is easier to design a lens for a smaller format and maintain a given level of quality through the manufacturing chain. Also, there are examples of crop camera/lens combinations out performing FF camera/lens combinations where both lenses are high end, disproving the claim that FF "always has" a resolution advantage and would only be worse with a poor lens. My 17-40L is not a "poor lens", but my 7D+Tokina 11-16 out performs it on a 5D mkII.
    But the arguments that smaller sensor systems will equal (or even exceed!) the resolution capabilities of larger sensor systems are specious.
    There are now multiple crop bodies which out resolve the early generations of FF bodies.
     
  40. So Daniel, then we can extrapolate from your logic that if cropped sensor DSLRs can produce the same system resolution as full frame sensor DSLRS that MF digital systems must not produce better resolution than full frame DSLRs and that four/thirds cameras must be able to resolve as well as cropped sensor cameras and, what the heck, point and shoot size sensors can resolve as well as four thirds, all of which logically proves that...
    ... point and shoot size sensor cameras can logically produce system resolution equal to that of MF digital systems with similar numbers of photosites.
    When I come up with a logical chain that points in directions like that, I always go back and re-check my assumptions.
    Dan
     
  41. There are now multiple crop bodies which out resolve the early generations of FF bodies.​
    This is a red herring. The debate in this thread concerns the current generation of full frame and crop bodies.
    Obviously the 7D out-resolves the 5D, for example; however, here we're comparing the resolution of, e.g., the 7D to that of the 5DII.
     
  42. Mark, that's why I didn't even bother to respond to it. Pretty silly comment, wasn't it...
     
  43. When I come up with a logical chain that points in directions like that, I always go back and re-check my assumptions.
    As you should. It is false to assume that what we observe between 35mm and APS-C holds true for all larger differences between two formats. (Fallacy of multiplication.)
     
  44. This is a red herring. The debate in this thread concerns the current generation of full frame and crop bodies.
    Your reading comprehension is poor. I was not addressing the debate but a specific claim made by a specific person.
     

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