Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

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Archive 2009 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Sam Bennett
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p.2 #1 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Here's some shots with the Sigma 50mm f/1.4 just farting around last night. The Sigma definitely seems sharper wide-open that the 50G (not that you can really tell from these photos).

Jan 16, 2009 at 04:11 PM

Joe Marques
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p.2 #2 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Well done Sam, very helpful comparison. Sigma does nail 1.4 if you like buttery smooth (I do). However, I too will be in the f1.8-f2.8 range more often than not with my Nikon so the difference isn't relevant to me.

I told a friend to buy the Sigma for his DX camera because I see it as a great alternative to the 85 1.4 on DX.

Jan 16, 2009 at 07:28 PM

Sam Bennett
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p.2 #3 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

For DX, I'd recommend going with the 50G since the vignetting and sharpness across the frame doesn't matter as much. I'd rather have the low weight and (ostensible) Nikkor build in that case.

Jan 16, 2009 at 07:32 PM

Joe Marques
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p.2 #4 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Sam Bennett wrote:
For DX, I'd recommend going with the 50G since the vignetting and sharpness across the frame doesn't matter as much. I'd rather have the low weight and (ostensible) Nikkor build in that case.

I prefer the smoother bokeh of the Sigma @ 1.4 and would exploit that more on DX given my shooting style (since I'd use it like the 85 1.4 on FX). I don't think there's a clear cut answer on which to buy for DX, it still comes down to usage and personal preference as always.

Jan 17, 2009 at 06:22 AM

tjny
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p.2 #5 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

linathael wrote:
better color contrast with the 50G, it is quite obvious with the open-air shots
+1

Jan 17, 2009 at 06:28 AM

Taylor Barrett
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p.2 #6 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

I think the shots from the Sigma look much better but the lens its self doesn't interest me that much because of high cost, huge front ring and size.

Jan 17, 2009 at 06:48 AM

Sam Bennett
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p.2 #7 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

So, I was noticing a bit of front focusing while shooting around the house and have heard complaints from other Sigma owners, so I figured I'd do a bench test. The results are not pretty. Did a series of 5 shots each using center, single point. Racked each lens to infinity first for each shot before AF'ing and shooting. Here's the best focused shot for each lens:

Nikkor 50mm f/1.4G @ f/1.4

Sigma 50mm f/1.4 @ f/1.4

The Sigma appears to progressively shift focus back as you stop down - by f/2.8 it is sometimes focusing as well as the 50G, but it is still generally poorer on average. Adjusting the focus +15 in the D700 definitely helps, but will force backfocus as you start stopping down.

Jan 17, 2009 at 05:41 PM

R. Francois
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p.2 #8 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Sam Bennett wrote:
So, I was noticing a bit of front focusing while shooting around the house and have heard complaints from other Sigma owners, so I figured I'd do a bench test. The results are not pretty. Did a series of 5 shots each using center, single point. Racked each lens to infinity first for each shot before AF'ing and shooting. Here's the best focused shot for each lens:

Nikkor 50mm f/1.4G @ f/1.4

Sigma 50mm f/1.4 @ f/1.4

and that was a real lemon. Send it back, this is not how it's supposed to be!

Jan 17, 2009 at 06:01 PM

cputeq
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p.2 #9 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Nice work on the comparisons. It's a shame Sigma seems to have focus issues with several of their lenses...it seems the general internet consensus is that you roll the dice with Sigma (and perhaps Tamron) and hope your lens focuses properly.

I'm wondering if perhaps the 3rd party lens makers have looser tolerances than 1st party, hence the focus issues more prevalent? I really wish there was a detailed walkthrough of how each manufacturer produces a lens...it would be enlightening.

Shame, too. I love the look of the Sigma's bokeh at f1.4

-----

This makes me wonder if future iterations of micro lens adjustments in the camera body will include an option to specify focal adjustments at certain apertures or focal lengths (for zooms)

Jan 17, 2009 at 06:57 PM

Chris Langer
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p.2 #10 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

What the best way to test out a lens? I know charts have been posted but if someone could throw me those charts I would greatly appreciate it!

Chris

Jan 17, 2009 at 07:04 PM

Kerry Pierce
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p.2 #11 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

That's about the same as with my sigma and d700, but mine isn't quite so much, around 10, I think. But, it is dead on with my d300. Some of my other lenses do the same thing with the d300 vs d700. I tend to think that my d700 AF is off calibration just a touch.

Jan 17, 2009 at 07:11 PM

Kerry Pierce
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p.2 #12 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Chris Langer wrote:
What the best way to test out a lens? I know charts have been posted but if someone could throw me those charts I would greatly appreciate it!

Chris

Here's one that I like, Chris. I changed it to have a light blue background to reduce veiling flare.
http://regex.info/blog/photo-tech/focus-chart#print

Jan 17, 2009 at 07:14 PM

Makten
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p.2 #13 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Sam Bennett wrote:
The Sigma appears to progressively shift focus back as you stop down - by f/2.8 it is sometimes focusing as well as the 50G, but it is still generally poorer on average. Adjusting the focus +15 in the D700 definitely helps, but will force backfocus as you start stopping down.

My experience is the same, but with the Nikkor. Focus shift has nothing with AF accuracy to do, since it derives from the optical formula of the lens. Almost every very fast lens does shift focus when stopping down, because of spherical aberration.
And remember that these lenses were not designed for closeups, so their performance when shooting focus charts should not be confused with "real" pictures. Of course some users will notice this when using the lenses for their purposes, but the problem is often neglible at larger distances.
Your Sigma is obviously focusing too close to the camera, but the focus shift is an optical design problem; not a malfunction.

Jan 17, 2009 at 07:40 PM

Sam Bennett
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p.2 #14 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Makten wrote:
My experience is the same, but with the Nikkor. Focus shift has nothing with AF accuracy to do, since it derives from the optical formula of the lens. Almost every very fast lens does shift focus when stopping down, because of spherical aberration.

I often hear this as an excuse, but I just don't buy it. Not every 50mm lens does it, in my experience. This was the excuse proponents of the Canon 50mm f/1.2L trotted out to defend its problems, but no one can give an answer with a straight face as to why the $1,500 50mm f/1.2L does it but the $275 50mm f/1.4 does not.

Makten wrote:
And remember that these lenses were not designed for closeups, so their performance when shooting focus charts should not be confused with "real" pictures. Of course some users will notice this when using the lenses for their purposes, but the problem is often neglible at larger distances.
Your Sigma is obviously focusing too close to the camera, but the focus shift is an optical design problem; not a malfunction.

Sorry, I don't buy it. I did notice it with "real" pictures, which is the only reason why I benched it. You don't notice it at further focal distances because the DoF is large enough to make it a moot point. But anyone shooting environmental portraiture would see this eventually, imo.

Jan 17, 2009 at 08:23 PM

Sam Bennett
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p.2 #15 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Just to be clear, I know that focus shift, conceptually, is a real problem - but it generally is not with modern lenses and indeed it doesn't appear to be a problem with my 50G.

Jan 17, 2009 at 08:31 PM

theSuede
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p.2 #16 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

Focus shift, mostly at close distances... I'd get the body calibrated first, and the lens after that. The Sigma's optical formula doesn't give very much shift (I tested aperturestepping in Manual Focus tethered from a VERY stable tripod and saw a small variation of center of focus, but unlike the L, it's nowhere from 1.4-2.8 large enough to put the original focus point outside the optimal focus plane on a D700, not even close!)

I think people trust electronic adjustments too much nowadays - having to adjust for a malcalibrated mirror electronically after the the focus-system has acquired its readout from the linesensor is kinda dumb... It's just begging for trouble when you swap lenses a lot. I think service-centers rely to much on calibration-by-USB-cable nowadays...

Get the basics covered first, go for advanced tactics later is my motto... Unfortunately for camera users/owners, getting the basics covered includes mechanical work - which the service-centers generally tend to avoid.

The focus-shift that you see MIGHT be coming from the fact that the camera's AF-system gives higher out-of-phase allowance ("focus acquired"-signal) for smaller apertures. If zero alignment is off, then the problem will show more with smaller apertures (the DOF center will shift MORE with smaller apertures than with large apertures). The problems you indicated combined says that the camera body is out of calibration.

Another thing.... When shooting test targets, NEVER use incandescent light to acquire focus and then take the shot with flash. The longitudinal CA might in a few unlucky cases make you miscalibrate by up to a cm/m... (with the 50L, up to two cm...). I know people that have gone half-mad from their inconsistent results when trying to calibrate.

Good shooting to you. Unless you're really out of luck, any of the two lenses mentioned should give you excellent end results (when everythings A-ok calibrated) !

Jan 17, 2009 at 09:23 PM

Sam Bennett
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p.2 #17 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

theSuede -
I get what you're saying, but I'm using the same process for the Sigma 50mm f/1.4, the Nikkor 50mm f/1.4G and I threw in the Nikkor 24-70/2.8G just for the hell of it. I don't think it's a testing issue or something stemming from the large aperture.

I personally would not be satisfied with "working around" the problem with the D700's adjustment system, even though it's apparently smart enough to know the difference between the Sigma and the Nikkor. I like the Nikkor, and if the Sigma has some sort of inherent issue the positive aspects of it would be completely outweighed by that.

Jan 17, 2009 at 10:00 PM

Sam Bennett
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p.2 #18 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

For what it's worth, I can completely see what attracts people to this lens. Wide-open, it has a really fantastic character and the bokeh in some cases can be quite obviously different than the 50G's. It's smoother is really remarkable. Here's a shot I got while testing focus accuracy between the two (the Sigma is still misfocusing). After testing I was noticing the difference in the one label, so these shots are actually manually focused to show the difference in bokeh. Believe me, this isn't just attributable to slight variances in the focal plane - even bracketing focus the Sigma stays super smooth on either side of "dead on". Very nice.

Sigma 50mm f/1.4 @ f/1.4

Nikkor 50mm f/1.4 @ f/1.4

The decision of whether to keep this lens or not will be very difficult. A lens that can't focus reliably is not much use to me, but there's no denying it - there is something special about this lens.

Jan 17, 2009 at 11:21 PM

Kerry Pierce
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p.2 #19 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

I am not convinced that the lens is the only issue with these types of problems and agree with the suede.

As I said, my new sigma 50 works with 0 adjustment on my d300, but needs FF correction on my d700. My 105 f/2 DC is the same way, for example. It needs even more FF correction on my d700 than the sigma, yet works fine on the d300. If the lens were the problem, it would be a problem on both cameras.

That situation changes dramatically for the worse, with test shots at MFD with both cameras. That's why I don't test normal lenses at MFD and why I won't use the Jackson test chart. I test all of my lenses and do fine tune adjustments at normal focus distances, which is at least 5 feet, preferably longer.

Jan 18, 2009 at 12:38 AM

Sam Bennett
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p.2 #20 · Another Sigma 50/1.4 vs. Nikkor 50/1.4G Thread

The test chart is just one part of a larger puzzle. Again - if I hadn't seen it in practical shooting, I wouldn't have bothered. If I continue to see it in practical shooting, then I will continue to be concerned about it. The test chart is just to try to understand, objectively, what may be going on with the lens. I see people talk about how their lens "isn't sharp", as though it's possible that when they were building it someone put an element in the wrong way or smeared Vaseline on it - where the truth is probably that there's a focusing issue of some sort - that's what the chart intends to expose.

Jan 18, 2009 at 03:52 AM

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