JATO: Scotomaphobia Eliminator
PS, whats with the big hammer, is that the fine adjustment tool?
We just use it as a threat - we tell the lenses we can do this the easy way or the hard way. Actually we had to tap in one of the desktops that had gotten a bit bent in shipping.
Debankur Mukherjee: Is Mr Cicala trying to prove that the D600 had no sensor dirt issue ?
Antony, that's exactly it. And over time the D600s have less dust than they used to, so it became less of a problem.
KariIceland: The problem with Lens rentals also is they send you the lenses with a CRAPPY UV filter on the front.
I can't speak for other houses, but Lensrentals does not send UV filters on lenses.
Plastek: Good test. Guys at LensTip.com made similar tests (only never published the results) and came to a similar conclusions - adapters are completely random and getting an acceptable one - perfectly centred with accurate flange distance - is impossible. That's why they test lenses on native bodies instead of comparing all of them in a single body and single sensor (what would allow cross-system comparisons).
So much for all these people thinking that shooting mirrorless with adapters is a valid way for photography.
I just want to throw my $0.02 in: I agree with everything in this series of comments. Like Iskender said, pixel-peeping gets frustrating and expensive, and like Andy said, it usually doesn't matter.
The point behind a lot of what I do is basically trying to say there are no absolutes in photography. When people say 'adapters don't have any adverse effect at all', they're wrong. When people say 'adapters always screw up the image', they're wrong, too.
The coolest thing about photography, to me, is balancing all the compromises so we get the best images. I guess I see my bit as pointing out where some of the compromises are so we can make educated decisions.
Every so often, I read an article and think, "man, I wish I'd thought of writing something like that." This is one of those. I enjoyed it immensely.
My first digital camera was actually an Apple QuickTake 100, which shows you how old I am.
photo nuts: The title and extract taken from Cicala's long article are SO MISLEADING. One should really go through the original article.
As Richard said we discussed this (and I will add I found the discussion useful - Richard and Shawn had good thoughts about why this might be occurring).
I thought the 70-200 f/2.8 data was the most interesting of the repair frequency data tand was appropriate to look at as a subset. A lot of us own those lenses. I've always tended to think because they're so well built they're bomb-proof, which turns out not to be the case.
doctorbza: I'm sure Roger is thrilled that his work has been filed under "Epic Fail".
It wasn't on the list (5% most repaired). We've only had the 70-200 f/2.8 VC in stock for 6 months or so, though, so it's early to say much other than looking good so far. Roger
Thank you, doctorbza! That just made my day :-)I'm sure a lot of people file most of my work under "Epic Fail". Roger
Philly: Amazing that he doesn't wear any gloves while doing this. Isn't there a risk of getting oil from the finger tips onto the components? It doesn't seem like a very good practice.
Some do wear gloves but I hate the loss of tactile feel that causes. I'd rather clean things if necessary during reassembly than strip a screw or tear a flex that was glued down during the disassembly of a lens for the first time. It's amazing to me how much fine sensation is lost by even a thin pair of gloves doing work like this. After we've been in a given lens a time or two and know what to look out for, it's less critical, but the first time I want everything on my side.
I keep my hands off any electrical contacts, touching those only with tools - rubber shod forceps - but generally avoid touching them at all. Same with glass elements.
If I do put on gloves its during reassembly which also includes a lot of cleaning with contact cleaner, alcohol, etc.
Samuel Dilworth: How can a lens have on-axis astigmatism? Clearly something’s wrong there: either the lens is improperly manufactured or the test is faulty, or both.
More generally, I’m not sure this is a particularly useful test:• it tests three good lenses, on-axis, near the middle of their zoom ranges, i.e. it minimises optical differences. Naturally this brings sensor differences to the fore. In the real world, the more important differences are off-axis, often with poorer lenses or good lenses at weaker settings• it compares a camera with an anti-aliasing filter to one without (or with a nullified filter), but no mention is made of the image processing techniques used, leading me to suspect no sharpening was applied. You might think no sharpening would level the playing field, but in this case it would prevent a useful comparison• it compares resolution at an MTF of 0.5, which is a poor substitute for comparing two images visually
It is what it is, but it’s not very practicable.
Thank you Samuel. It's something I'm trying to figure out as we learn this new equipment. Those are helpful points.
This is a very pertinent point and one I can't say I understand completely. The graphs printed are for single lenses, but the results consistent with each of three copies.
The bench lens mounts were an obvious question, but the Tamron lenses were the same on both Canon and Nikon mounts, so I don't think the mount is an issue.
I don't know the answer, but here's one bit of data we've seen on numerous zooms: many show slight on-axis astigmatism at one area of the zoom range but not at others. I don't think element tilt would cause an on-axis asitmatism (it certainly makes off-axis go crazy) but I believe an element spacing issue could. My thoughts, since this seems more common in zooms, is element spacing can't be perfect throughout the zoom range - at least not given current manufacturing tolerance.
But that's just my current thought. Perhaps some of the people with more optical physics than I can confirm or correct that.
h2k: The news item's wording seems to indicate some kind of promotional intent in favour of the lens rental service. The news itself could have been explained with a less promotional flavour. Yet the story was surely worth to be on DPR - also as a good change to the usual - and it caused some entertaining commentary.
If there were no pictures we'd send him replacement gear. As long as there isn't water in the lens, it's covered. Pictures of the event are a fun bonus, but have nothing to do with replacing the equipment or covering the damage.
taotoo: If LensRentals is financially connected to this site have we been told?
Lensrentals has no financial connections or arrangements with DPR.
OK, let me condense this: We are establishing a monopoly in order to serve you better.
AbrasiveReducer: Hi Roger - Since we're talking about pixel peeping and focus fine tuning, can you explain why you say the 28-75 Tamron is "...the best lens nobody knows about, and possibly the best bang-for-the-buck of any camera lens, period. Its nearly as sharp as the Nikon 24-70 , particularly on DX cameras, but much smaller, lighter, and cheaper...." I realize your remark about DX hints that the Tamron has soft corners but this seems like reading between the lines. Variations? I've had 4 of these lenses, with and without the motor and none has been particularly good. Granted, the alternative costs a lot more but the difference is equally dramatic; the 24-70 has sharp corners on FX.
My take on the Tammie is several years old, written when the vast majority of photogs were shooting crop bodies (as opposed to less of a vast majority today, I guess). It is weak in the corners on an FX but on a DX I feel it's a bargain: 80% of the performance for 30% of the price. But more than that I was coming from the other direction: in the under $500 lens category there's this and the Tamron 17-50 as the f/2.8 zoom entries. Both are decent lenses at an amazing price, but neither is going to compete with a $1,500 lens wide open.
taotoo: Very informative article (as were your previous ones), but a couple of queries:
"If they are out-of-spec and get by quality control, then someone, somewhere gets a truly bad camera or lens. It doesn’t happen frequently, but it happens. When it does, it isn't a subtle call; it's very obvious the lens is bad."
This doesn't stand up to reason - it suggests cameras/lenses SLIGHTLY out of tolerance always get caught by quality control.
"The reality though is that the only sensible definition of 'best' is 'best with the camera body you are using,'."
And best at your chosen focal length, aperture, focus distance etc...
I didn't mean to infer that slightly out of tolerance lenses get caught. Poor wording on my part. Rather I was suggesting that an occasionally awful lens does get by. Not often, but sometimes.
And good point about focal length, aperture, etc.
Hiram P Bumblesniger: What are you measuring on these graphs? There are no labeled axes. Without telling us what the graphs are really showing, how can we assess anything? Please add x and y axis labels. The graphs are pretty meaningless without them. Thanks.
Trying to keep graphs in the allowed image size made the labels too small so I identified the axis in the text: Both axis are MTF50 in Line Pairs / Image height. The horizontal axis is center point resolution, the vertical is average resolution of the entire lens.
MalbikEndar: > something like 150 +/- 2 MHz
Are you sure you don't mean KHz? 150 MHz is very implausible for an ultrasonic motor.
You are absolutely correct - I typoed that. Roger
Leonard Shepherd: It is an interesting article - but how reliable is it?Roger uses an example of a screw diameter - screw diameter does not affect assembly tolerance, though it might cause tightening issues.In "whats it all about" point 5 there seems to be a misunderstanding of how AF works. If starting AF front infinity and then minimum focus gives different results the size of the parallel part of the target is not big enough relative to the length of the AF detection line. What is happening is the AF is detecting detail further away coming from infinity and closer from minimum focus that would not occur with a bigger target. This is not "tolerance variation".I agree lens and body variations likely to show in a 20 inch wide print are rare. If you have fast broadband this link I got from dpreview indicates the various electronic test stages in assembling a Nikon 24-70 - and includes a Nikon AF test target.http://lens-club.ru/public/files/pdfs/4b4fb97547c5d54819491c07c715f2c2.pdf
Leonard, for the example I use the same result occurs focusing on a star chart on a flat wall: there's nothing in front of or behind the target for the autofocus system to detect.
em_dee_aitch: .... Continued from last post: So when you say that your technicians can easily detect a "bad lens" but not distinguish among the acceptable "variations" in your chart, I think you are conveniently omitting cases in which the lens may be within the acceptable variation at the test point within the frame (or even on average) and yet be yielding images which are to some degree easily detectable as of asymmetrical quality to the naked eye. I bring up this omission because it is the primary mode of failure that I believe reasonable people can easily spot without going so far as Imatest or even charts.
Actually I completely agree (and a great example of the same definition meaning different things to different people). But I consider theses one of the easily detectable "bad lenses". Optically it's readily apparent as a portion of the image not nearly as sharp as the rest. Imatest shows it as acceptable peak sharpness with bad weighted average sharpness.
But I think you've given me a nice lead for a new article: I can definitely do some examples of this.