Nikon 50mm f/1.4 AF-S G review

[David Kilpatrick]

For once, the British Journal has actually put up the entire text (but not the illustrations) for one of my reviews on their site without paid access!

http://www.bjp-online.com/public/showPa ... age=836697" onclick="window.open(this.href);return false;

I do 2 or 3 reviews a month for the BJP - camera and lenses - and because I am commissioned and paid for print and web rights for these, and they obtain the loan cameras sent to me, I am unable to put my own reviews on line (it would be competing with a fairly generous freelance contract). Most of the reviews are paid-only access, but this one they have let out of the bag. Next week, the Sigma 50mm f/1.4 HSM - week after that, the Tamron 70-200mm f2.8.

I will be able to post a Sigma review here, as I obtained a Sony fit sample after doing the first tests using the D3X, and this was not at their request - I proposed the article. I will wait until the BJP has published before doing so.

David

[Javelin]

Thats cool. does that mean you make a little extra on this article compared to the usuall ones ?

[bakubo]

Interesting article. I especially like the explanation about the focus shift when stopping down and what AF cameras do. I have a question though about this sentence:

"The only solution that works is a fast lens that has minimal focus shift, so it will work with cameras using standard AF sensors (f/5.6 type) or fast-lens compatible sensors (f/2.8 type), with bright laser screens or with pure matt screens."

Specifically my question is about the part in italics after the 'or' in the sentence. How does that work? If you have an f2.8 or faster lens and the body has an f2.8 AF sensor so that it focuses at f2.8 instead of f5.6 (like the regular AF sensors do) and then you stop down and the focus shifts how does the f2.8 AF sensor help?

[Dusty]

Nice article, David. I hope tey post more of your work on publicly accessible portions of the site.

Dusty

[David Kilpatrick]

Interesting article. I especially like the explanation about the focus shift when stopping down and what AF cameras do. I have a question though about this sentence:

"The only solution that works is a fast lens that has minimal focus shift, so it will work with cameras using standard AF sensors (f/5.6 type) or fast-lens compatible sensors (f/2.8 type), with bright laser screens or with pure matt screens."

Specifically my question is about the part in italics after the 'or' in the sentence. How does that work? If you have an f2.8 or faster lens and the body has an f2.8 AF sensor so that it focuses at f2.8 instead of f5.6 (like the regular AF sensors do) and then you stop down and the focus shifts how does the f2.8 AF sensor help?

That's why I said the only solution is to have a fast lens with minimal focus shift - so it does not matter what method you use, and what your final apertur is, focusing at ANY effective aperture will still be correct.

Zero focus shift = focus always right, no matter.

The old Minolta 50mm f1.4 has some focus shift, but for whatever reason (internal programming in the camera, maybe) this does not show up on the A900 as much as it does with the A700. That is another solution, but I have nothing to prove that Sony has done anything in firmware to tackle this. I just see better results and wonder whether they have.

David

[01af]

If you have an f/2.8 or faster lens and the body has an f/2.8 AF sensor so that it focuses at f/2.8 instead of f/5.6 (like the regular AF sensors do) and then you stop down and the focus shifts how does the f2.8 AF sensor help?

It doesn't. The focus will always shift at smaller apertures, no matter whether the camera is using an f/2.8 AF sensor or an f/5.6 AF sensor. Focusing always will happen with the lens wide open anyway.

The old Minolta AF 50 mm f/1.4 has some focus shift, but for whatever reason (internal programming in the camera, maybe) this does not show up on the A900 as much as it does with the A700. That is another solution, but I have nothing to prove that Sony has done anything in firmware to tackle this. I just see better results and wonder whether they have.

I don't think Sony has done anything to handle focus shift. With the A900, I see the AF 50/1.4's focus shifting quite obviously ... but I don't know how bad it is with the A700.

David, months ago you said the A900 behaves very benign with old glass designed long before the dawn of the digital age and often yields film-like results. You suspected the unusual wide distance between AA filter and sensor to be the reason ... well, or one of the reasons. In the context of my AF micro-adjustment tests I noticed a strange phenomenon---at very high magnification (100 % - 400 % screen view), images focused at slightly different distances will appear equally sharp. Not equal but equally sharp. For example one may show better contrast; the next, focussed an inch or two shorter, may show less longitudinal chromatic aberration and better detail by a minuscule margin but less contrast. So the visual acutance is about the same (which by the way makes AF micro-adjustment no easier). In a way, this is pretty similar to what would happen on thick-emulsion film. And I guess this behaviour also tends to reduce focus shift ... at least to a degree.

-- Olaf

[Javelin]

Is it possible your software and video card are conspiring and adding in some anti aliasing and you notice it when when you zoom that far?

[I noticed a strange phenomenon---at very high magnification (100 % - 400 % screen view), images focused at slightly different distances will appear equally sharp. Not equal but equally sharp. For example one may show better contrast; the next, focussed an inch or two shorter, may show less longitudinal chromatic aberration and better detail by a minuscule margin but less contrast.
-- Olaf

[bakubo]

That's why I said the only solution is to have a fast lens with minimal focus shift - so it does not matter what method you use, and what your final apertur is, focusing at ANY effective aperture will still be correct.

Hmm, okay maybe I am just misunderstanding this sentence then:

"The only solution that works is a fast lens that has minimal focus shift, so it will work with cameras using standard AF sensors (f/5.6 type) or fast-lens compatible sensors (f/2.8 type), with bright laser screens or with pure matt screens."

It appeared that you were saying there are 2 solutions:

1. a fast lens with minimal focus shift with standard f5.6 AF sensors

or

2. f2.8 AF sensors with any fast lens

I read it again I can see what you meant though. I read it several times to mean there were 2 solutions. I couldn't understand how #2 could help.

The old Minolta 50mm f1.4 has some focus shift, but for whatever reason (internal programming in the camera, maybe) this does not show up on the A900 as much as it does with the A700. That is another solution, but I have nothing to prove that Sony has done anything in firmware to tackle this. I just see better results and wonder whether they have.

Do you mean that the A900 firmware may be adjusting focus after AF if the chosen aperture is wider than f5.6 because it knows the focus will shift?

[David Kilpatrick]

Do you mean that the A900 firmware may be adjusting focus after AF if the chosen aperture is wider than f5.6 because it knows the focus will shift?

Well, that is what the original calibration system from the 7D onwards was all about - except that it calibrated an f1.7 50mm to be used at f7.1, not full aperture.

Since there is no longer a 50mm f1.7 made, it would rather silly for Sony still to be used that lens for factory calibration. So, I guess they may well use a 50mm f1.4 - and they may also with the A900 be setting it for best focus at f2.8 (now that there is an f2.8 sensor). Such a compromise would mean it was still acceptable at both f1.4 and f8 or smaller apertures.

I did a test using the outer sensors a few days ago and there was a more significant shift in the expected focus plane, so I would say that the A900 is calibrated optimally for a 50mm (f1.4) used at f2.8 with the centre sensor active. The A700 appears, to me, to be calibrated exactly the old way using the 50mm f1.7 bench system. Maybe someone can find the factory service manuals, as they did with the D7D and D5D, or the part number for the new calibration system lens.

David

[NealS]

Can you comment on how the Nikon lens compares to the Sigma 50/1.4?

For once, the British Journal has actually put up the entire text (but not the illustrations) for one of my reviews on their site without paid access!

http://www.bjp-online.com/public/showPa ... age=836697" onclick="window.open(this.href);return false;

I do 2 or 3 reviews a month for the BJP - camera and lenses - and because I am commissioned and paid for print and web rights for these, and they obtain the loan cameras sent to me, I am unable to put my own reviews on line (it would be competing with a fairly generous freelance contract). Most of the reviews are paid-only access, but this one they have let out of the bag. Next week, the Sigma 50mm f/1.4 HSM - week after that, the Tamron 70-200mm f2.8.

I will be able to post a Sigma review here, as I obtained a Sony fit sample after doing the first tests using the D3X, and this was not at their request - I proposed the article. I will wait until the BJP has published before doing so.

David

[David Kilpatrick]

Yes. At full aperture, f1.4, it is no way as good. The Sigma is sharper and has less aberration round the edges of the frame, though some difference exists between centre and edge. The Nikon clearly has more spherical aberration, but this also means it appears to have slightly more depth of field, and that AF is less accurate. Because the Sigma has such a clean image, AF (which is determined by f2.8 performance on the Sony, but as far as I can tell by f5.6 performance on the D3X) is very accurate indeed.

But - the Sigma does not sharpen up as well across the entire frame as the Nikon, or indeed the old Minolta, and it doesn't have quite as a flat a field as close focus. It concentrates best resolution over a wide central zone, and slightly sacrifices stopped down resolution at the periphery. This means that the Nikon (and the Minolta) around f8-11 can produce some sharper details away from the centre of the image when you are taking close-ups.

I haven't really gone into this in my BJP test next week, because overall the Sigma is well ahead, and it is the first lens to produce such a low degree of full aperture vignetting and such exceptional (portrait to distant focus) f1.4 performance across the frame. The big difference really is that the Sigma does not need even 1/3rd stop stopping down to give a totally clean image. The Nikon needs 1/3rd of a stop. The old Minolta is surprisingly good and even 1/3rd of a stop improves it, but really it needs to be set to f2.8 for an image approaching the Sigma's f1.4 clarity and clean rendering.

I will be posting some full size 24 megapixel examples when I have time. Right now I'm testing the Tamron 70-200mm on the Canon 50D, write-up urgently needed! I already tested it on the D3X, was not happy with the focusing, so had to arrange a Canon copy and a Canon body to see if it made a difference. It does.

David

[Dusty]

Right now I'm testing the Tamron 70-200mm on the Canon 50D, write-up urgently needed! I already tested it on the D3X, was not happy with the focusing, so had to arrange a Canon copy and a Canon body to see if it made a difference. It does.

David

Hmmm. Did we ever have such problems with manual focus? I never went to AF film camera because I believe that I did a better job (and a faster one) than the early AF SLRs. There are still times, of course, when I have to shift to manual, but the kit lens, especially, is not well suited to that. I guess old habits are hard to break!

Dusty

[Greg Beetham]

I agree with you Dusty, I always thought AF was a lazy approach to photography so I only recently mothballed my X700's (about four years ago now though, time flies), but having used AF now for a while it certainly has it's benefits, there are some shots that only AF can do, that fleeting moment type shot that is so hard to get with MF, so AF has won me over for the most part though the AF-MF switch does get used occasionally.
What I never noticed was that the focus changed within the f/stop range of a lens at a given focus setting, that's a new one on me, I initially thought it must be operator error, such as moving the camera back or forwards slightly after focus confirmation and before the shutter actuation, but that would be mostly meaningful at close focus distances and not so critical at long and towards the infinity end of focus.
Then I thought that it must be some error in the calibration of the lens to sensor plane distance vs lens to focus screen distance, but that's not really it either, as David and Olaf say the focus can change at different f/stops with everything else remaining the same? Too my mind that's the critical point, "IS" everything else remaining the same?? ie. camera to subject distance for example.
It just seems ridiculous that every lens has too be tested at all f/stops and at a large range of distances for focus variations and notes made for future reference, I find it difficult to believe or even possible that a given camera could have the entire lens inventory and focus distance f/stop variations "in memory" to refer too when making an exposure, and adjusting accordingly.
Greg
btw. I wouldn't complain if the f/stop ring was put back on the lens either....where it belongs.

[Dusty]

btw. I wouldn't complain if the f/stop ring was put back on the lens either....where it belongs.

That's another thing you have to get used to, especially since I was mostly (and still am) an aperture priority man. I've always felt, from early on, that controlling depth of field was most important 95% of the time. I got so used to that that I rarely used shutter priority mode. Most times I thought I need ed to freeze action, I'd just open up the f stop.

Having to turn a dial, then hold a button to turn the dial again in manual exposure is just too weird.

Dusty

[bakubo]

btw. I wouldn't complain if the f/stop ring was put back on the lens either....where it belongs.

I got into SLR photography in the early 1970s, all manual (focus, exposure -- stop down ttl metering) so I was accustomed to having the aperture ring on the lens too, but since 1988 I have been using AF (first was a Minolta Maxxum 7000i) and, I think, that it is probably generally better for people who use zoom lenses (most people these days) to have the aperture controlled by the thumb or shutter finger. The hand holding the lens is often busy adjusting the focal length so it is nice to be able to adjust the aperture with the other hand.