peter_nelson1

<i>coma -> chromatic aberration -> CA.

 

(?) :-) </i><br><br>

 

Coma is not CA.

<i>Peter... Great! You found a lens that will make you happy! That's all that counts! </i><br><br>

 

I wouldn't go so far as "happy". One way to look at it is that I just paid over $1000 for what may be the worst lens in my collection. It's tied for the slowest lens I own with my 300 f/4, but the 300 is a remarkable piece of optics - sharp across the frame at all apertures and virtually no distortion - whereas the 12-24 is a collection of compromises.<br><br>

The problem is that no one makes a really outstanding lens when you get down in to the 20mm range and below. ALL of the wide-angles seem to have issues - CA, corner-sharpness, flare or something. When I buy lenses money is pretty much no object, so I'm not used to the idea that I can't just spend my way into a better lens like I can with other focal lengths. <br><br>

 

<i>Just a quick question, sorry for my ignorance but what is "coma"? I never heard of that before! Uhmm! I'll google it! Cheers! Rene'</i><br><br>

 

Coma is a type of optical aberration where details are smeared out away from the center of the image. Here's a link to the wikipedia entry<br><br>

http://en.wikipedia.org/wiki/Coma_(optics)

<br><br>

and here's an image of it . . . <br><br>

http://www.ryokosha.com/eng/products/prod_img/nh/nh_MA__pin_coma.jpg

Last week I returned a Tokina 11-16 to the dealer after it failed my incoming

qual tests and replaced it with a Nikkor 12-24. (The Tokina appeared to have a

decentered element) I just ran through some initial tests on the 12-24 and here

are my impressions. (Note that most of my tests were at 16mm because that's the

focal length I intend to shoot at. So far I've just glanced at the other focal

lengths)

 

At f/4 (wide open on this lens) center sharpness is phenomenal. In last week's

test I was criticized because after shooting some tests of a Wall Street Journal

on a wall at 16mm from about 10ft away, I then set up my Nikkor 24-70 from

farther away so that I'd get the same framing at 24mm. People complained that

this was unfair because, they said, wide angles are not designed to shoot

sharply that close. Well, I'm happy to report that the 12-24 beat its longer

cousin in that same test, which should put concerns about the distance to rest.

 

I ran my edge and corner sharpness tests and CA tests outside in perfect

cloudy-bright conditions. At f/4 the edges and corners are soft but they improve

by f/5.6 and improve more by f/8, which seems to be the sweet spot. They never

get as sharp as the center and the problem seems to be coma. I would rate

sharpness as "acceptable" at the corners and edges at f/5.6, and "good" at f/8,

but the corner and edge sharpness will never knock your socks off.

 

Editorial comment: Why don't more lens-test websites test for coma? I do some

astrophotography and one thing astrophotographers encounter regularly is coma

because our subjects (stars) are perfect point sources of light, so any coma in

the lens shows up easily. Most lenses have it worst wide-open, which is how

astrophotography is done. I've never seen a lens wider than 50mm that didn't

have some coma. I've tested two 28mm lenses, two 24mm lenses and a 35 (Nikkor's

legendary 35 f/2) and they all had it in spades. On normal (non-star) subjects

coma shows up as a kind of smearing outward, especially at the edges and corners

and that's what I'm seeing in this lens.

 

CA at the corners and edges was noticable at all apertures, but it was easier to

correct in NX PP at f/5.6 and f/8 because the CA (like everything else) was

sharper and better-defined at those apertures.

 

I did a quickie distortion test and it's pretty bad (barrel) at 12mm but it

turns to pincushion at 24 but at my preferred focal length, 16mm, it's not

noticable, so I got lucky on that.

 

Mechanically this lens feels less substantial than most of my other Nikkors,

probably because it has more plastic. This seems, somehow, disappointing, in a

$1000+ lens, but I suppse they know what they're doing. On the other hand I

bought this lens for one thing and one thing only - hiking with a heavy pack at

10,000+' in Yosemite, so its light weight is appreciated. It's an AF-S lens but

the focussing on it is noticably louder than my 24-70 and 70-200, although

nothing like my non-AF-S lenses.

 

This lens seems to be pretty good, and most of the test websites rate it as good

as or better than Nikon's primes in the same range, but its limitations are

still very noticable. I think the world is still waiting for a really good

wide-angle lens.

"Why can't they keep up with demand?"

 

How do you know they can't? Nikon sets its prices once a year. They are due for an adjustment in the next month or so. Since they last set their prices the dollar has dropped 16% versus the yen. Maybe they are assigning the hard-to-get lenses (300 f/4, 70-200, 24-70) to markets with a more favorable exchange rate.

 

I predict that when they make their next adjustment (upward) suddenly there will be a better supply. I've been making this prediction for a month or so, but a few days ago one of the stores where I was wait-listed for the 300 f/4 AF-S asked their Nikon rep when they might see more of them and he said August. That would match my prediction very nicely.

The 70-200 VR on a D300 is a breathtaking combination.

 

And I mean that literally - it's so heavy you get out of breath picking it up. 21 elements - solid glass. And seriously, on the D300 the results are fantastic - center sharpness beats the Canon and the other metrics are equally impressive. On an FX body, maybe not quite so great, especially at the edges, but it's still heavy.

You must have the compression craked too far up. That camera has multiple JPEG quality levels. You should set it at the highest quality it offers. Or, as someone else said, shoot raw.

I found the non-AF-S one to be VERY hand-holdable. A couple of days ago I sent it in to exchange for a used AF-S version at KEH so I'll let ya know about that one. But just keep in mind that it's 300 mm so you need to shoot at a MINIMUM of 1/500th for decent sharpness, and really 1/1000 would be better, so use it with a camera with decent high-ISO performance such as the D300 or D3.

 

BTW, GOOD LUCK finding a 300 f/4 AF-S in stock anywhere!

I have both and they are both fantastic lenses. In pure test-chart sharpness I think the 180 wins, especially wide-open. It also has better contrast and fewer internal reflections, for obvious reasons.

 

As a low-light walking around lens the issue is way more complicated. VR buys you at least a couple of stops. I've got pretty steady hands but even I would not want to rely on the 180 for sharp work at less than 1/200th of second, unless I could brace it on something. Last night I was testing my 70-200 at /100th and 1/50th - it was great at 1/100th and about half the shots at 1/50th were also real sharp (at 200 mm) . On the other hand that lens is one heavy monster.

I'm glad Lex enjoyed his 24-120 VR, but there is a currently-active thread right now on FredMiranda.com about the 24-120 VR where it seems like every poster has a worse story than the prior one about how bad it is! Several people have suggested it's the worst lens Nikon makes! Check it out:

 

http://www.fredmiranda.com/forum/topic/648653

"Peter, if you are indeed interested in the Tokina 11-16mm/f2.8, I find it very strange that you gave up on it immediately after merely one sample in your hands."

 

I've never had to return a Nikon lens due to a sample defect. I currently own 9 Nikkors and over the years I've probably owned twice that many more. BTW, in the past I owned all sorts of other brands - Tamrons, Tokinas, Sigmas, Vivitars, etc. What happened to them all? Did I sell the or lose them? No, one by one they fell apart. I remember a 3 week trip 17 years ago to Australia with 2 FM2's, 2 Vivitar Series 1's, a Sigma 400, a Tokina zoom, and a Nikkor 35 f/2. I returned home with the 2 FM2's and the Nikkor 35 intact (And they still work today!) but all the other lenses came home in a box having just plain fallen apart).

 

I'm sure Nikkor produces the occasional lemon but it's clear to me from years of reading P.N, Nikonians, FM, etc, that the rate of sample variation is WAY higher on the third party lenses than on the pro-level Nikkors. (I don't know about the consumer-grade Nikkors) .

 

When I added up all my hours wasted on the Tokina - outside shots, indoor shots, uploading the images to PC to compare, and eventually arranging for the return, packing it up, taking it to the Post Office - if I was making my professional pay scale it would easily have paid for the price difference with the Nikkor. As I said, the prior one was also defective but luckily they mounted on a body before shipping it to me.

 

You can be sure I'll test the Nikkor 12-24 just as thoroughly - it will be easy because I've still got the targets up on the wall and the tripod spots marked on the floor of my studio. And I can tell you now that I do NOT have high hopes for it - it will be my first DX lens (unless you count the 70-200 f/2.8 VR 8-) ), it's slow to start with, and it's a zoom. And no one makes a really good wide-angle if we use the same standards of "good" as we do with longer focal-length lenses WRT resolution, coma, CA, distortion, and contrast. The current crop of 10-24mm lenses from all makers are pretty marginal based on all the tests I've seen. That's THE best argument for FX format cameras - lenses seem to get a lot better at 24mm and up.

 

Why Nikon never chose to make a decent wide-angle prime is a mystery - their 14mm and 20 mm f/2.8's are only regarded as mediocre - Photozone shows the 12-24 besting both of them on resolution tests and distortion.

<i>"I agree that the real design challenge for the future will be to produce sensors that give excellent noise free images with very low light The new CEO of Kodak wrote a recent editorial about this issue. His main point was that since photography developed we have been forced to use sources of artificial light due to the technical limitations of our equipment. He went on to say that we all see in natural light and the challenge for the future is to develop cameras that see well in natural light under all conditions.

"</i>

<br><br>

 

If you REALLY want a camera that can function in natural light then the challenge is to improve the <b>DYNAMIC RANGE</b> of cameras. Current cameras are fall <b>HORRIBLY, GROSSLY, WAY</b> short of of our own visual systems when it comes to dynamic range. Which means there is no camera today that can record most typical indoor or outdoor scenes the way they look to our own eyes.

I have a similar problem with the D300 - I find the left-side grip too shallow for my (maybe slightly larger-than-average) hands. On some discussion forums some people have reported accidentally pressing the lens-release button. I've come close to that a few times. But otherwise I find the D300 to be the best camera body I've used in 40 years of SLR shooting. Everything has its tradeoffs.

"To Peter Nelson: at most you can claim is that you had one bad sample of the Tokina 11-16mm/f2.8. "

 

And that's the most I DID claim. Did you see me make any other claim about the 11-16's?

 

That 3rd-party optics have a high rate of sample variation is well known. You can read postings all over P.N., FredMiranda, Nikonians, etc, about people having to buy multiple copies of such lenses to get a good one. This is the second 11-16 I had ordered (from Roberts Imaging, a major midwest dealer). The first one was found to be defective in the store! So for me that's 2 out of 2 defective 11-16's.

 

The main point about this Tokina was that it was so egregiously bad (witness the "Bold 36" image) that it's a wonder how Tokina let it out of the factory. To me this suggests they can't possibly be testing these lenses much before shipping them.

 

Just out of curiosity, what do YOU think mainly accounts for the price difference between Nikkors and Tokinas? Is it all just Nikon profit?

"If it's going to be years, if it were me, I'd use ebay or photo.net classifieds to store them in someone else's camera bag and store their money in my bank account."

 

Excellent, and well-stated advice! Really, what's the point of keeping a lens in storage for years anyway?

"Look for technical discussions not hype."

 

OK, here's a hype-free technical discussion (actually, a full technical review) . . .

 

http://www.dpreview.com/lensreviews/nikon_70-200_2p8_vr_n15/

f/5.6 is a little slow, expecially because most consumer zooms need to be stopped down one of two stops to get really sharp results. That will prevent you from using a fast shutter speed, which could be problem for kids and sports.

The test sites show it to be remarkably sharp for a consumer zoom.

 

But are you sure you can live with an 85mm lens that only opens to f/5.6? Not only is that too slow for some autofocus systems in anything but bright sunshine, but it really limits your range of shutter speeds. Even though the VR lets you shoot OK at slower shutter speeds, if the SUBJECT is moving VR doesn't help.

The Tokina at 16mm was about 10 feet away and the Nikkor at 24mm was about 15 feet away, so that the image was the same size in both cases.

 

And N.B., that the Tokina was very soft in my outside shots as well - when I was testing for CA by shooting trees above my roof, the roof tiles were very soft. (I'll be happy to post images if anyone cares)

 

There's just no way to get around the fact that this Tokina sample was very soft. If you look at the "Bold 36" images it's clear that there is something wrong with the lens - probably a decentered element. That would explain why the NX CA-reduction tool behaved the way it did.

Someone wanted some image samples. Here are some 100% crops from last night. Notice that the Nikkor at f/2.8 is slightly sharper than the Tokina even at f/4.

 

http://pnart.com/temp/wsjpg.jpg

 

Below is a shot of a printer test image, both the Nikkor and Tokina at f/4. Besides the dramatically better sharpness and contrast of the Nikkor, the other thing to notice is the weird way that the Tokina is out of focus. On the text "Bold 36 Point" note the the B l d and P letters are all darker on the left and softer onb the right. It was like this in all those shots and almost looks like motion blur except that this was triod-mounted at 1/500th of a second.

 

http://pnart.com/temp/bold36.jpg

<i>"...so as Robert Heinlein might say, TANSTAAFQC!"<br><br>

I think there's a 3- or 4-letter limit on Internet speak (LOL, IMHO, YMMV, etc.).</i><br><br>

 

It's not internet speak.

 

It dates back to 1966 from Robert Heinlein's novel "The Moon is a Harsh Mistress" and the acronym TANSTAAFL means "There Ain't No Such Thing As A Free Lunch". The term is widely used in economics and was a popular expression of Milton Friedman's. I just replaced "lunch" with "Quality Control".

"Could you post a sample of "horribly soft"? I'm not having any experience remotely like this with mine."

 

I'll try to put a few up on my website in a day or 2. But really I have no idea what your point is WRT to your experience with this lens. We're not talking about your copy; we're talking about the one I'm sending back.

 

"The Tokina 11-16mm/f2.8 is not a macro lens. Instead of the newspaper test, I would try to shoot something from 15 feet to infinity."

 

Earlier in the day I was running some tests on it to examine CA by shooting the roof of my house and tree branches against a cloudy-bright sky. that's when I first noticed that it was soft. BTW, in using the NX CA-correction tool I noticed that when it corrected the CA in one part of the image the CA would get much WORSE in other parts of the image on this lens. This is consistent with the thesis that this lens has some sort of alignment defect because that would result in non-uniform CA.

 

"If you do the same test with the Nikkor, you will likely get the same results, or, according to what I've been reading, perhaps it'll even be worse!"

 

If it is I'll send that back too. I've been doing incoming qual tests on my lenses for 35 years and I've never seen one this bad, so it's unlikely the Nikkor could beat it.

 

"(Dirty Harry quote...) That's a pretty broad statement. Actually some of the third party lenses are pretty stellar. "

 

The question isn't whether they can make a stellar lens; it's whether they can do so CONSISTENTLY. The big knock on the 3rd parties is that they have a lot more sample-to-sample variation. With my Canon gear I have an excellent Tammie 28-75 f/2.8 that's sharper (and lighter) than the Canon 24-70 "L" f/2.8 I was trying. And I got it on the first try. But I know of THREE(!) other people who had to exchange their first copy of the Tamron for another one, including one who exchanged his first two copies.

The Tokina 11-16 lens is half (or less) the cost of the various competing Nikons, so as Robert Heinlein might say, TANSTAAFQC!

 

. . . actually there is - it's US - we're Tokina's "free" QC! But if I valued my time at the same rate I would professionally, the time I spent testing and returning the Tokina would easily pay for the price difference with the Nikkor.

I took delivery of a Tokina 11-16 that I just got in the mail yesterday, and I spent the

evening testing it.

 

My copy was just HORRIBLE wide open. I taped some copies of the Wall Street

Journal to a wall, very brightly lit and shot a series of images at 16mm, at f/2.8, f/4,

and f/5.6 at ISO 320 with my D300. Prior to doing this I noticed that it was already soft

so I tweaked it in AF Fine Tune to its best adjustment (approx -15).

 

As a control I shot the same wall with my Nikkor 24-70 at 24mm, f/2.8 at a slightly

farther distance so the framing was the same (i.e., the details were the same size on

the image). The lighting was bright enough that at f/5.6 the shutter was 1/125th and of

course everything was shot on a tripod. At each setting I took 3 shots and picked the

best one incase I bumped the camera or something.

 

The results were that I had to stop the Tokina down to f/5.6 to match the Nikkor wide

open. It was VERY disappointing! Wide open, the Tokina shots were not merely soft,

but they were soft in a weird way - on thick, black letters one edge of each letter was

noticably sharper and harder than the other. It looked like motion blur except that it

was consistent with every shot and at f/2.8 I was shooting at 1/500th of a second ON

A TRIPOD.

 

I think there's an alignment problem with this lens. I know some people have the 11-16

and love it, but the problem is that the third-party lens makers spend less money on

QC than the average fratboy spends on opera tickets, so they have huge sample-to-

sample variation. Whenever you buy a third-party lens it's like Dirty Harry - "Do you

feel lucky? Well, do ya punk?"

 

I've sent it back to the dealer and I'm exchanging it for a Nikkor 12-24. All my other

nine lenses for my Nikon bodies are Nikkors - the Tokina would never have fit in.

And BTW . . .

 

"I expected to have a 315mm lens. "

 

If you want a 315mm lens you have to buy a 315mm lens. On a D70 all you get is a cropped 200 mm lens with no more detail or magnification than a 200 mm lens on a full-frame DSLR or film SLR.

If this is the AF-S VR 70-200, it must have power on the DSLR turned OFF when it is mounted. All kinds of crazy things happen if you have the camera is turned on when you mount it.

 

 

Turn the camera OFF. Remove the lens. Put the lens back on. Turn the camera back on.

"This has to happen at some aperture less than full, because not all lenses are the same speed/size-of-hole, and the system has to focus all of them. So the manufacturer picks a width--say f5.6, and all lenses focus with that effective aperture, not wide open--glass outside the borders of where the RF system is looking is ignored. When a smaller aperture is used, half of the split-image blacks out because you can slide your eye left or right to include one or the other side of the slightly-blocked aperture hole, but not both at once. That's why the effective focusing aperture is less than that of the lens. To make up for the resulting zone-of-no-feedback in the center of the range on larger apertures we compensate for by racking focus back and forth to center between equally out-of-focus areas and hopefully find the focus point within the dead zone. "

 

I don't see how this would work with a modern multipont focussing system where the user can arbitrarily select his specific focus point. As I said, I use single-point, and over the weekend I was shooting an oriole in an apple tree with my 300 f/4 where there were lots of branches at various distances all around and in front of and back of the bird. I had no trouble putting my focus point exactly on the bird and focussing just on him.

 

Can you please point us to a source of information on your thesis as it applies to a modern DSLR? Thanks in advance.