peter_langfelder

I would suggest taking the lens off the camera and taking a good look through the lens. Look for possible dirt inside (hair maybe?), aperture defects etc.

<p>I __think__ the image circle diameter D with extension L would equal (image circle without extension)*(L+ exit pupil distance)/(exit pupil distance). The image circle without extension should be about 43mm (could be more on some lenses). The problem is finding the exit pupil distance, most manufacturers do not seem to specify it in their data.</p>

<p>The maximum aperture limit has nothing to do with the amount light. Aperture also limits the angle at which the light strikes the AF sensor. Wider apertures mean wider angles. Phase-detection AF sensors need light from two different directions separated by a certain minimum angle, and the smallest angle that the AF sensor can work with corresponds to aperture 5.6.</p>

<p>Steven, correct - phase detection AF is in principle the automated version of the split prism focusing screen while the contrast detect AF is the automated version of ground glass focussing. The details of the implementation differ though. I don't know the details of modern contrast detect AF implementations, but I would be very surprised if it were just trial and error. One can certainly quantify contrast and after about 3 measurement one can predict where the contrast maximum will be, move the lens directly there, make another measurement and refine the prediction.</p>

<p>This is not directly an answer to the OP's question, but it may also help: I also have problems with lumbar discs and have found that the important issue is not how much weight you carry, it's how you carry it. If you can get a backpack or waist bag with a good waist belt that transfers most of the load to your hips, your spine doesn't have to carry any extra weight. I found that especially with a good backpack, carrying even relatively large loads (5D, 24-70 f/2.8, 70-200 f/4, filters, tripod, water, etc) for extended periods causes no trouble. Again, the important feature is that the suspension can transfer the load straight down to the hips, with nearly none resting on the shoulders, while keeping you comfortable.</p>

<p>The cooler is a nice idea, but I'd rather not use any water or ice near the lens, I think the risk of the (melted) water spilling is far greater than the risk of the lens overheating. I live in southern California and while car interiors are often too hot to touch because of direct sunlight, I don't ever recall the inside of a car trunk being too hot to touch, which means the temperature stays under 50C (120F). I would guess that using a black lens outside in full sunlight could get the lens warmer than being in a closed trunk; in other words, I would not worry about the temperature. If you want to be extra-cautious, bury the lens in some clothing/blankets on the bottom of the trunk.</p>

<p>I upgraded from the original 24-70 to the version II. The difference at 70mm was big, less so at the shorter focal lengths. I suspect that my old 24-70 may have had a bit of a problem at the 70mm setting where I simply could not get a picture as sharp as the 70-200 f4L IS, while the new 24-70 was very similar to the 70-200 at 70mm. The old 24-70 was clearly inferior to my 50mm f/1.8 at the same apertures; the new one was very similar, maybe even a bit better at 2.8. The new lens also has better contrast than the old one.<br> My suggestion would be to compare your 24-70 to the 70-200 you have, and any other primes you may have in the 24-70 range - the new 24-70 is comparable to the primes and the 70-200, so if the old one is clearly inferior, the upgrade makes sense.</p>

<p>A 50mm lens should focus to 3m with about 0.86mm extension - for a simple lens, the formula for extension is, if my math skills haven't failed me yet,<br> extension = (d-sqrt(d^2-4*f*d))/2 - f<br> where d is the focusing distance (distance between object and image (film/sensor) plane) and f the focal length.<br> A very good and much simpler approximation is<br> <br />extension = f*f/(d-2*f)<br> This formula is not exact but the error should be of order (extension/d), which in this case is negligible; in fact both formulas give 0.86mm and you'd have to go to the 4th digit past the 0 to find a difference. So it would seem your adapter is 0.86mm too short.<br> For the 90mm lens, I get an extension of 2.8mm at 3 meters - you would get the same 0.86mm extension at roughly 9.5 meters.</p>

<p>Mark, is the 568EX running in TTL mode? It needs to be in TTL mode so the 622N under it can control it. It is also possible that you have to put the controller on a camera for it to work properly.</p>

<p>Umm, so you get the 16 MP photo downsized to the resolution of the screen which is at best 2 MP, probably more like 1.5 MP because of aspect ratio differences, the enlarging lens presumably anti-aliases (i.e., blurs) even the few leftover pixels and you can print "exhibition-ready" prints up to 20x20 cm (8x8 inch)? Those prints must be very "artistic" (blurry). I can see the coolness of it but can't imagine many people using for more then a few prints, especially when the smell of the stop bath and the fixer starts stinking up their place.</p>

<p>Haven't seen this discussed yet - Canon announced the <a href="http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ef_50mm_f_1_8_stm">next iteration</a> of their 50mm f/1.8 lens, this time with stepper focusing motor. It's great that Canon finally updated the 50mm lens, keeping it small, light and cheap (same price as the old 50mm 1.8). The optical design seems more or less unchanged - even though the press release claims improvements, the MTF curves posted by Canon seem awfully similar to the old 50 1.8. At least the aperture now has 7 blades, no more pentagonal OOF highlights.</p>

<p>The focus-recompose technique assumes you have a lens with a flat field of focus - if the field of focus is curved, focus and recompose will certainly lead to poorly-focused photos. Just sayin'...</p>

<p>I haven't shot with 5D Mark III but the iTR AF is supposed to be able to stay on subject by switching between focusing points when subject moves within the frame. You just have to make sure that the subject is under active AF point at the start.</p>

<p>It also never hurts to replace the backup battery, which on a 5D Mark II may be up for replacement around this time (5 years). When the backup battery becomes weak, the camera acts up in strange ways.</p>

<p>I haven't shot BW film for a long time, but my advice for Neopan 400 would be to go no higher than ISO 800. Xtol may not be the best developer for pushing, IIRC it was billed a developer to get fine grain with slightly lower than "box" speeds. Rodinal used to be recommended for higher speeds although it did produce more sharply defined grain. I did shoot Neopan 400 at something close to 800 (it may have been 640 or perhaps 500) and developed in Rodinal, which I thought turned out OK (to my taste) but I still preferred shooting at ISO 250-320 and developing in Xtol 1+1. <br> As for ISO 1600, I found that difficult even with Neopan 1600 (which is no longer available). I used to develop it in Xtol 1+3 with less agitation, but still got too much contrast (hard to print, may be OK for scanning). I assume that pushing Neopan 400 to 1600 would result in even more contrast, nearly blocked highlights and empty (black) shadows.<br> If you do decide to try Neopan 400 with Xtol, you could start exposing at ISO 800 (one stop underexposure from ISO 400) and developing for about 12-13 minutes in Xtol 1+1 at 68 F (20 C). If my memory serves well, I used to develop Neopan 400 in Xtol 1+1 for about 10 minutes when shooting at ISO 320, using a couple of inversions at each full minute for agitation.<br> Lastly, this may not be the advice you're looking for, but I'd try to use a tripod or some other way of stabilizing the camera and lens, or, perhaps, giving digital with a modern sensor (usable ISO 3200) and a stabilized lens a thought.</p>

<p>Thanks for the correction. I guess AF tuning is more dangerous than I thought.</p>

<p>Sorry, your explanation does not seem to make sense. The tuning is supposed to make the lens focus on the right spot, including infinity. It is much more likely that the optimal focus tuning depends on distance, or you perhaps made some mistake in determining the value of -6 for close focus. If you can, focus by live view which is most accurate.</p>

<p>My 5D Mark II shows the flash exposure compensation icon whenever flash exposure compensation is set, whether a flash is attached or not. So your problem may not have anything to do with flash.<br> Have you replaced the backup battery recently (or at all)? When that battery drains, the camera starts behaving in weird ways that may not look like they could have anything to do with the backup battery (mine stopped autofocusing). If you haven't replaced the battery in the last few years (or ever), try replacing that first. See this information for how to replace it (scroll down to the section Back-up battery):<br> http://cpn.canon-europe.com/content/education/infobank/batteries/care_of_batteries.do<br> HTH,<br />Peter</p> <p> </p>

<p>How far is your second flash? Something seems to go wrong with the flash communication, perhaps you're pushing the distance limit (100 ft if memory serves correctly)? It could also be that the communication between the camera and the flash fails is some subtle way - is your on-camera flash securely fastened and are the contacts clean? FWIW, I once had the exact same problem with a 580EX+430EX II combo using optical wireless ETTL flash. I never really figured out what the problem was and wasn't able to replicate it since.</p>

<p>I'd have to see the curves and their explanation from Kodak, if any, but I'd guess that the high blue and green density reflects the orange mask. The developed film has higher density in blue and green colors, meaning it absorbs more light of those colors, meaning the physical color of the film (when you look at the exposed and developed negative) is orange, which makes sense. When you (or a machine) prints the film, the orange base is compensated for by the color balance of the light shining through it and possibly also by the paper the photo is printed on.</p>

<p>If you know your preferred aperture with 35mm film, simply double it for 6x7 while doubling the focal length as well. For example, if you shot a 50mm lens on 35mm camera at f/11, take a 100mm lens for a 6x7 and shoot it at f/22 for approximately equivalent field of view and depth of field. For 6x6 you could stay about half a stop below doubling (around f/18 on 80mm lens).<br> Shooting at f/32 on 6x6 is about equivalent of shooting at f/16 to f/18 on a 35mm camera with the same field of view. You will start running into diffraction softness at these settings.</p>

<p>Zion and Bryce are beautiful. Zion is about 3-4 hours from Las Vegas, sits at an elevation of 4000 ft (1200 meters) and is generally pleasantly warm to somewhat hot in April and May. Bryce is at double the elevation and it can still snow in April (probably less so in May). The drive between Zion and Bryce is a about 1.5 to 2 hours if memory serves right and is quite scenic.<br> If you visit Death Valley, you may as well spend a day or two to drive to the Eastern Sierra. The mountains will most likely still be snowed in, but you can at least see Mono Lake and the Ancient Bristlecone Pines in the White Mountains near Big Pine. <br />To get to Yosemite, you have to drive from Death Valley back down to Mojave, then to Bakersfield and then to Yosemite. It is impossible to cross the Sierra Nevada (Tioga Pass) since the roads are snowed in and closed. Along the way you can also stop in the Sequoia and King Canyon national parks which are really beautiful and streams (and waterfalls) will have lots of water in April and May. So it's quite a drive from Las Vegas, but certainly worth the trouble.<br> Google maps (and driving directions) is your friend, look up each national park and connect them by roads.</p>

<p>The depth of field would be roughly the same if the subject is roughly the same size in the viewfinder, since at 200mm you'd have to stay about 3 times as far as at 70mm. The blur of objects at infinity will be about 3 times larger with the 200mm zoom setting at the same magnification, if my math serves me correctly. All of my statements are approximate since they apply to an ideal simple lens, and the zoom is anything but simple (for example, the effective focal length decreases when focused closer).</p>

<p>Tom, I think you nailed it. There may be significant focus shift when stopping down (also known as residual spherical aberation). Trying focusing at the working aperture, not wide open (or shoot wide open when focusing wide open). The focus shift due to RSA often seems to be most pronounced at short focusing distances. <br> <br />I am familiar with the 550D but on my cameras (5D MII, 70D) in live view the lens is stopped down to the aperture you set on the camera, not wide open.</p>

<p>"Best" is subjective, but in my view the best way to print a transparency is to scan and print from a scan. If your goal is high-quality prints (as opposed to transparencies viewed on a light table), even better IMO is to shoot digital from the start.</p>