david_klaffenbach

<p>Hi Ellis, I'm fairly certain it starts as a specular highlight off of glasses, an aluminum beer bottle or something else shiny. It's an afternoon shot, so it's sunshine at work. What I'm not sure about is why it isn't a smooth circular pattern (which is what I get if I try to make this happen with out-of-focus streetlamps or such).<br>

The lens is old but new to me, and it has more internal dust than any of my other lenses, but I don't think that's the cause of this and the lens appears to be working well in general. It was once a rental lens, so I'm sure it's had its share of photon impact damage (which by the way is a real thing if you're dealing with high intensity lasers - they call it optically induced damage!).</p>

<p>I shot this the other day:<br>

<img src="https://i.imgur.com/rJyxhfp.jpg" alt="" width="510" height="339" /><br>

I was struck by the appearance of some of the out-of-focus highlights, such as seen in this crop from the upper left corner:<br>

<img src="https://i.imgur.com/xGi7Wmf.jpg" alt="" width="462" height="495" /><br>

I've since found similar patterns in photos by other folks online (and it happened to be in daytime baseball shots), so I don't think it is due to a lens defect particular to my lens.<br>

I'm just curious if anyone knows what the explanation is for this kind of background pattern. The lens is a Tamron 300mm f/2.8, shot at f/4.</p>

 

<p>NMF = nose magnification factor</p>

<p>I just made this up, but maybe it will help. Maybe not.</p>

<p>Suppose you are taking a tight shot, with a magnification (minification really) of 15, such that (on DX) the subject frame is approximately 240x360 mm (roughly 9x14 inches). If you shoot at 12 mm focal length, the subject distance will be 12*15 or 180 mm, and assuming the nose is 25 mm in front of the eyes and the ears are 100 mm behind the eyes (I just made those up but bear with me), then the nose will be imaged with a 80% larger scale than the ears, hence the caricature-type result (distance to ears = 180+100, distance to nose = 180-25, 280/155 = 1.80). As you go to 85 mm, I get a NMF of 10%, suggesting (if we take as a given that 85 mm on DX gives a pleasing result) that we are used to a perspective with that kind of NMF. A 180 mm lens gives an NMF of 5%, and 360 mm gives only 2%.</p>

<p>But if we do a wider type of shot, say double the minification (subject frame is now 480x720 mm or 19x28 inches), then the NMF of 85 mm is only 5%, 180 mm 2% and 360 mm 1%, yielding a smaller difference in how the face is rendered based on focal length.</p>

<p>I believe all the examples I've seen online (including the ones mentioned in this thread) are flawed by using human models who can't stay perfectly still during the lens and shooting position changes. For a better test, one should use a life-size bust, fix the lighting and carefully keep the optical axis the same throughout. I don't have a bust laying about though.</p>

<p>My practical take has been that I use the longest lens that is convenient if I want to reduce the background to a smooth blur of color, and for me that's a 180/2.8. But next time I'm going to shoot a few tight head shots with the doubler (360mm!).</p>

<p>I have not tried that combination (I'm a Nikon user) but it is likely that a teleconverter and a 70-300 won't perform well together. 70-300 zooms tend to get soft when zoomed longer than 200 mm, and a teleconverter needs to be of high quality and be used with a lens that is sharp when used by itself. On top of that, at 200 mm your zoom is f/5, so the combination will be 400 mm f/10, or 600 mm f/11, which will be very difficult to focus or get adequate light to make use of.</p>

<p>I have a cheap 4-element doubler - if I use it with my 180/2.8, the results are worse than uprezzing images from the 180/2.8 without the doubler, so it is useless. On the other hand, I have an older 7-element Tokina doubler, and when combined with the 180/2.8 and used in the right conditions, it does provide a bit more detail than I can get with just the 180. My guess is that the 70-300 zoom isn't outresolving the camera at the long end, and that even a perfect doubler (if there were such a thing) would just magnify the blur along with the image and give no more detail.</p>

<p>Unfortunately, there is no way to get 500 mm capability which is both high quality AND inexpensive.</p>

<p>I like this reference <a href="http://www.trenholm.org/hmmerk/#TIAOOF">http://www.trenholm.org/hmmerk/#TIAOOF</a>.</p>

<p>It is just one example (there are many) of a preferred number sequence (see <a href="http://en.wikipedia.org/wiki/Preferred_number">http://en.wikipedia.org/wiki/Preferred_number</a>), in this case apparently chosen for ease of use and manipulation while preserving more than adequate precision. You can trade stops of aperture for stops of shutter speed without worrying about the small error you might be leaving on the table. I'm not sure who first created these sequences (for aperture and shutter) but it arose during the era of slide rules when understanding of appropriate level of precision for a given problem was much more prevalent than today, when we can easily (and by default) generate as many digits of an answer as we care to take the time to read.</p>

<p>As an aside, I have my camera set on 1/2 stops rather than 1/3 stops for the aperture and shutter speed controls to make adjusting exposure faster and to expand the range shown by my spot meter. In principle, this means I might only be able to get within 1/4 stop of the "correct" exposure rather than 1/6 stop.</p>

<p>Hi Paul,</p>

<p>Can you be more specific? What lens are you using and at what kind of apertures and focus distance?</p>

<p>Are you using focus confirmation in camera or is this a camera/lens combination that doesn't provide that?</p>

<p>Interestingly, the 75-240 is the longest (in terms of physical length) Nikon lens to have a plastic mount, and one of the heaviest.</p>

<p>Source: <a href="http://www.photosynthesis.co.nz/nikon/specs.html">http://www.photosynthesis.co.nz/nikon/specs.html</a></p>

<p> </p>

<p>Andrew, That reminds me of something I learned while shooting basketball (where there are often nice contrasty objects like brick walls or bleachers behind the players). The focus sensor areas are not identical to the marks denoting their locations in the viewfinder. If you put your camera in single-point, center, continuous mode, and slowly sweep across something like a telephone pole against sky, you'll get an idea for how big the sensor area is. If the subject is smaller than that, and the background isn't uniform, then it starts to be uncertain where the camera will focus.</p>

<blockquote>

<p>More relaxed: just clean off the lens with your shirt tail, LOL.</p>

</blockquote>

<p>That's me!</p>

<p>Hi again Gwyneth,</p>

<p>Are there specific situations in which auto focus isn't working for you?</p>

<p>Do whichever you want or need. If I'm using an AF lens I almost always use AF, although usually in continuous, single-point mode, much of the time but not always on the center sensor, and using the lock button in order to recompose as necessary.</p>

<p>I find it more reliable and faster than manually focusing, although that comparison is obviously a personal one. I've shot a lot of basketball and while I know people used MF for everything in the past it would have been very difficult for me to get many of the shots.</p>

<p>I occasionally use MF for situations where I'm shooting through chain link fence, or there's a bit of foliage in front of the actual target and the AF system doesn't do what I want. I have a couple of MF lenses and I have a doubler which is MF so when using those I have no choice and it forces me to slow down a bit.</p>

<p>I think it's a good skill to be able to quickly focus manually, but I'm not so skilled. Also, DSLRs don't have the focus aids that film cameras used to have and on small-sensor cameras the viewfinders are smaller. Manually focusing on my D90 is harder than it was on a Pentax K1000.</p>

<p>So while I usually shoot in M, and set ISO and WB manually per the situation, I usually do use AF.</p>

<p>I'm not sure what you mean by "manually focusing and then using BBF to lock".</p>

<p>Hi Cosmin,</p>

<p>I had read those threads and looked at your comparison shots - thanks for putting that up there. About all I found digging was an old B&H advertisement from 1981 listing a Tokina 135 2.8 for $67.95, and an Olden Camera ad in the same magazine listing the Nikon 135 2.8 for $208.</p>

<p>Well, I own it now and am forming my opinion on it, but was curious about it's design and its history.</p>

<p>So far I can say that it is not useful at f/2.8 (low contrast and loss of definition, glassy looking), but is decent from f/4. Not quite as good as my 85/1.8 AF-D or 180/2.8 AF, but those are tough competition. Focus ring is quite smooth with about 190 degrees of travel. Very compact (about the same size as a Nikon Series E 135/2.8).</p>

<p>I got it for when I want to have a very lightweight kit - something to go with a Vivitar 19/3.8 and a Nikkor 50/1.8 AF-D.</p>

<p>Hi,</p>

<p>I've recently acquired a Tokina RMC 135mm f/2.8 lens to play with, and I'm curious about the specifications of the lens and its history but I can't find much at all on the web.</p>

<p>Anyone have any old literature on this lens?</p>

<p>Not that I really need it to use the lens, but I'm curious.</p>

<p>Thanks</p>

<p>I'm a Nikon shooter, but I don't think that makes much difference. I think you should try some primes, except for the very wide end where no one makes them.</p>

<p>I use a 12-24/4 (Tokina), 30/1.4 (Sigma), 50/1.8, 85/1.8 and 180/2.8 (Nikon, but Canon has essentially the same lenses). The fast primes open up a whole different world of shooting, from portraits to indoor sports. At the least, go grab the 50/1.8 (it's quite inexpensive) and see what you're missing.</p>

<p>To use a 70-200/4 you must have some really bright gyms. f/4 and ISO 1600 would put me around 1/60s in most of the gyms I've been in.</p>

<p>Having shot around 200 basketball games in the last six years, I would recommend the 85/1.8 as the first lens you want. Many high school and [NCAA Division III] college gyms are no brighter than ISO3200, f/2, 1/500s and some a bit darker. In these gyms, an f/2.8 lens will not give enough shutter speed or will drive you to very high ISO settings. A 55-200mm consumer zoom will be useless.</p>

<p>You can use other lenses for a change, such as a 50 mm for under the basket stuff, or an f/2.8 zoom (or the 180/2.8) for longer work in a bright gym, but the 85mm will be the most productive lens.</p>

<p>I've assumed that it's not generally possible to hold a camera as still at arms length as it is when holding it tight to your face, so that would put it in the "cons" column. Also, as I get older, and start to "play the old trombone"*, it's even worse. On the other hand, I haven't seen a good experiment on this - it would be interesting to know how many stops are lost.</p>

<p>* become presbyopic and have to hold the LCD even farther away in order to focus on it</p>

<p>My (mostly) prime kit used with a D90: Tokina 12-24/4, Sigma 30/1.4, Nikkor 50/1.8, 85/1.8, 180/2.8. </p>

<p>If I were buying it now, I'd substitute the Nikon 35/1.8 for the Sigma 30/1.4 (the 35/1.8 didn't exist when I bought the Sigma).</p>

<p>You could simplify this to the three lengths I use the most: 12-24/4, 35/1.8, 85/1.8.</p>

<p>Just to be clear, the 80-200/2.8 that I said was slow to focus was the oldest of them, the non-D version with a rotating ring for the focus limit selector.</p>

<p><a href="http://www.photosynthesis.co.nz/nikon/lenses.html#70-xxPro">http://www.photosynthesis.co.nz/nikon/lenses.html#70-xxPro</a></p>

<p>How about a 180/2.8?</p>

<p>I had a push-pull 80-200/2.8 for a while but found it to be heavy and slow to focus. No complaints on image quality though. I was using a D50 at the time - now a D90. I eventually got a 180/2.8, which isn't a speed demon but is about twice as fast to focus as that zoom. I have a better hit rate shooting basketball with the 180 than I did using the zoom due mostly to the focus speed and I believe I can get the 180 on target more quickly (half the mass). For the short end of the zoom range I use an 85/1.8. I love the feel of the 180, it just handles very well and draws nice pictures. Mine is a non-D version from the late 80s - I bought it before the D3 came out and paid only $300. Best deal I've made on a lens so far.</p>

<p>I suspect it is due to the spot metering, but I have a question for folks: Why would one use spot metering in any automatic exposure mode? You would only get a correct exposure if the spot was on a piece of subject with the appropriate tone, which isn't likely to happen accidentally, and trying to use exposure compensation to correct for that would be possible but would slow one down greatly.</p>

<p>It seems to me that one should use center-weighted or matrix metering in the automatic exposure modes (P, A, S or M w/ auto-ISO) and that spot metering should only be used in M w/ auto-ISO off, to allow you to take readings of various parts of the scene by aiming at them and considering where you would like those tones to fall (as an abbreviated zone system).</p>

<p>Regarding focusing on the crowd instead of the player - there are at least two causes:</p>

<p>1) The focus points aren't infinitesimal points; they have some area. If that area includes a portion of a player and a portion of crowd (or brick wall) then it may well focus on the background. This is more likely to be a problem with wider lenses or longer distances to the players. When I've used a 30mm or 50mm it happens to me more than with the 85mm.</p>

<p>2) The other obvious reason is that you missed the target for a moment, focused on crowd and shot. It happens.</p>

<p>I set focusing to AF-C, center point only, and then I focus either on waist, numbers or face depending upon distance to the player. Best focus is achieved by tracking the player for one second or so. Composition comes later by cropping.</p>

<p>I've shot several tens of thousands of frames of basketball (enough to wear out a D50), mostly with the 85/1.8. I'm convinced the 85/1.8 is the best solution for the non-professional. By non-professional, I really mean someone who can't afford an FX body and 70-200/2.8. A 70-200/2.8 on a DX body generally doesn't work so well for basketball at high-school and smaller colleges as the gyms are too dark.</p>

<p>A few of my basketball shots can be found here: <a href="https://picasaweb.google.com/dklaff">https://picasaweb.google.com/dklaff</a></p>

<p>Hi Glenn,</p>

<p>I'm curious what you're really trying to do. As I see it, there's no law that says a properly exposed image will have an average luminance of 12.8% or 18%, although presumably if you take a large number of photos that expert photographers judge to be properly exposed, they will <em>average</em> to something in that range, which is a rationale to set a camera meter to something in that range.</p>

<p>Dave</p>