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g dan mitchell

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g dan mitchell last won the day on December 12 2008

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  1. <p>Shutter life estimates do not provide a point at which the shutter <em>will </em>die — they provide an estimate of a point at which the manufacturer anticipates that a (small but significant) percentage of the units might begin to have problems. It is possible for a shutter to fail earlier... and it is <em>likely </em>that your shutter will continue working long after that point.<br> Unless you have far, far exceeded this estimated value it probably doesn't make a lot of sense for most photographers to replace a camera just on that basis.</p>
  2. <p>Some people (not here) speak as if there should be "no noise," but there will always be some noise in digital photographs, and you can find it if you go looking for it. But that very small amount of normal noise is not a problem and you should not worry about it.</p>
  3. <blockquote> <p>That is just for a small perspective correction. You are arguing it doesn't matter, I tend to agree, but it does not mean that the performance of the tilted 35/2 with software correction is the same as say a tilt-shift lens equivalently shifted.</p> </blockquote> <p>Hmmm... I did not say it is "the same." What I did say (and provide some evidence for, I think) is that making such corrections in post does not degrade the image in a visible way, and that this approach is an entirely viable one, even for rather large prints.</p> <p>A lot of forumtography writing is more about theory than reality. I've found that it is a good idea —and with digital it is often pretty easy, too — to actually check these things. I recall first "getting this" after I had spent a period of time avoiding apertures smaller than f/8 because "diffraction blur will soften you photographs." Then I made some photographs at various apertures and inspected the actual results and found out that the whole thing was overblown.</p> <p>There are some things that TS lenses can do that you can't really do in post, but it is perfectly fine to make typical small corrections to barrel/pincushion distortion and some perspective distortion in software and the results are excellent.</p> <p>Dan</p>
  4. <blockquote> <p>Here we disagree; it is not gimmickry, but it most certainly is not necessary. I shoot both digital and film, with the same lenses - how come on digital distortion correction would be necessary, while it would be perfectly fine to leave it as-is on film? Lens corrections are nice-to-have, but not the end-all-and-be-all of imaging. Let's not act like it makes the critical difference.</p> </blockquote> <p>The "not necessary" argument is a slippery slope. You could argue that roll film is "not necessary," but rather is just "nice to have." You could say the same about reflex camera designs, filters, tilts and shifts, color filtering in film printing, use of papers with different contrast grades and surfaces, the quality of lighting used when prints are displayed, and just about anything else.</p> <p>I would argue that if your photography benefits from the ability to correct or otherwise alter the captured image in post — as it traditionally and still almost always does — then it is "necessary" for your photography. The fact that the world will continue to rotate on its axis whether or not we can correct CA in post doesn't render the ability to correct CA unimportant.</p> <p>I don't understand how this is such a big deal. If being able to minimize or eliminate barrel/pincushion distortion, fix CA, improve image sharpness, etc. are possible and can improve some photographs, why wouldn't we want these capabilities?</p> <blockquote> <p>"...but even then G Dan admits there is sharpness reduction"</p> </blockquote> <p>I think you may have accidentally left our adjectives such as insignificant or invisible in your paraphrase. My point was not that "there is a sharpness reduction," but that these corrections can be applied in the majority of cases with <strong>no visible deterioration</strong> of the image, even as a rather large print.</p> <p>On a different topic and not directly related to the above quote: Anyone making a big deal out of the fact that digital capture "distorts" the image needs to slow down and think this through a lot more carefully. Film capture also "distorts" the original image in a number of ways, and the very act of making a photograph is far, far from what some imagine to be a "capture" of the objective reality of the subject of the photograph.</p> <p>My motto is that "photographs always lie." And that is a Good Thing. And I'm not joking.</p>
  5. The raw file supposedly contains the original luminosity data from the individual photo sites. The truth is slightly more complicated. Lenses don't "see" anything. Sensors sort of do "see" something transmitted to them through lenses, but rather than "see," it is more accurate to say that they register or record luminosity values.
  6. <blockquote> <p>"Remember, you can't "maximize the result in the field" if your shooting digital. The capture process introduces errors and the Raw conversion process can correct errors and/or add errors."</p> </blockquote> <p>The point you are trying to make here is unclear to me.<br> <br> dan</p>
  7. <blockquote> <p>"Still, those lens correction technologies - which are not part of the lens - should you really be testing a lens with those enabled to see what the lens is capable of? It's seriously a question, but obviously I have my doubts.<br />The capabilities of the camera and software should be excluded or normalised as much as possible when testing a lens. If you want to test a total system with the lens as an integral part of a chain, it's a different thing. But if the lens has chromatic aberrations, distortion or whatever, lens testing should reveal it - not hide with software optimisations. Or am I completely missing a point now?"</p> </blockquote> <p>I'm of two minds about this. What we are really interested in is what level of photographic quality we can produce using the equipment — not the specific measured performance characteristics of the lens per se. When we use the equipment to make photographs we don't do so with one arm held behind our backs. We always use whatever techniques and features are available to us to optimize the image.<br> <br> Imagine that you had two lenses. One was natively quite good — good resolution, good control of various sorts of distortion, and so forth. The other was natively almost as good but not quite, but when used on your camera its software compensated for the slightly lower performance by correcting various sorts of distortion and, after doing so, the image quality from this second lens was better than that from the first.<br> <br> Which is better? Which would you rather use to make your photographs?<br> <br> While I see the objective value in understand the underlying uncorrected lens capabilities, I've often thought that rather than trying to isolate everything that a more interesting and useful test would be to put two pieces of gear into the hands of a very skillful photographer (or photographers) and see what the end result would be when everything is optimized in precisely the way that skillful photographers will optimize them.<br> <br> Dan</p>
  8. <p>"Distortion correction will be destructive at the pixel level as one can't stretch, eliminate, or duplicate pixels without losing detail: if one worries about such things."<br> <br> Well, yes, but...<br> <br> It turns out that the potential for loss of detail is often greatly overestimated by those who haven't done a lot of such correction in post. If the corrections are not of a huge magnitude, you usually cannot see the difference even in very large prints.<br> <br> I posted a few examples at my blog:</p> <ul> <li><a href="http://www.gdanmitchell.com/2007/09/16/a-test-correcting-lens-distortion-in-post-processing">Correcting Lens Distortion in Post-Processing</a></li> <li><a href="http://www.gdanmitchell.com/2009/02/20/a-test-correcting-perspective-in-post-processing">Correcting Perspective in Post-Processing</a></li> </ul> <p>Dan</p>
  9. You can also just look at the subject in the viewfinder and place things where they look right. Dan
  10. <p>I wonder if you really need a collar on the f/4 lens. I've had two of those lenses, and I never felt that I needed it.</p> <p>dan</p>
  11. <p>If she wants a t3i, get her a t3i. It is a fine camera. The 18-55 IS is a fine starter lens. If she needs a longer zoom, the EFS 55-200 is a similar lens in a longer focal length range.</p> <p>Canon and Nikon both make fine cameras and lenses, and either is fine. If she has a preference for one over the other, then get that brand.</p> <p>Another thought... you could consider finding a way to let her make the actual decisions and then paying for the gear as the present.</p> <p>Dan</p>
  12. <p>Your 50mm f/1.4 lens serves as a fine, large-aperture, short telephoto on your cropped sensor camera.</p> <p>If I understand correctly, you may be asking if there is an add-on device that will let you "zoom" with this lens. The answer is no.</p> <p>There are other inexpensive prime lenses that can give you a bit more reach with a reasonably large aperture. These include the Canon EF 85mm f/1.8 lens and the 100mm f/2 lens.</p>
  13. <p>With three such different lenses, I think you are "barking up the wrong tree" by using supposed "image quality" as your decision point.</p> <p>Basically, ALL THREE of these lenses produce very good image quality. (I have extensive personal experience with two of the three, and the reputation of the third is well known.) When looking at a group of very good lenses and trying to decide among them, almost all photographers can simply assume that image quality will be fine, but that FUNCTIONAL differences need to be right for what they are trying to accomplish photographically.</p> <p>Do you need the reach of the 100-400 lens? If yes, then that is the only realistic choice for you among these three lenses. If not, why would you consider a 400mm lens, with its additional bulk, weight, and cost?</p> <p>If you don't need more reach than that provided by a 200mm lens, why consider the others? If you do need more reach, you would not want to get the 70-200.</p> <p>Dan</p>
  14. <p>"But I think that's what Canon might try to stop. I'm not quite sure how they legally can (that would be price fixing) but I'm sure it's what they'd like to do."<br> <br> I'm no lawyer, but my take on this is that while the retailer is free to lower the price "in the cart," Canon could (try to) enforce a prohibition of advertising the fact that the price would be reduced in that way. In other words, the retailer could not say: "$100 off. Add to cart to see the lower price!"</p> <p>That's the sticky point, isn't it? Apparently I can sell you a $1000 list price item for $900, and you and I can even negotiate a price of $900, and I <em>think </em>I can tell you personally that I have a special price for you once you come into the store and we start talking... but there is some boundary between that and <em>advertising </em>the offer to sell at the $900 price as a way of inducing you to buy.</p> <p>Confusing...</p>
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