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Sigma 50mm f1.4 review
- Thread starter mfbernstein
- Start date
Octane
Veteran Member
I see it's not that easy to measure just the lens resolution.
One question about the Nyquist frequency. If that is the maximum the camera can resolve how can you measure above that? The sharpness curve of the Sigma at f/5,6 goes way above. That would be impossible to measure. I must be missing something.
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-------David-------
http://flickr.com/photos/childish/
One question about the Nyquist frequency. If that is the maximum the camera can resolve how can you measure above that? The sharpness curve of the Sigma at f/5,6 goes way above. That would be impossible to measure. I must be missing something.
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-------David-------
http://flickr.com/photos/childish/
Andrew Westlake
Veteran Member
Yes, you know what I mean...
(We actually drop these little 'errors' in simply to test the proof-reading abilities of our forum users.)
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Andy Westlake
dpreview.com/lensreviews
Fair enough. I agree with the principle as stated. It's perfectly reasonable.
But aren't you penalising Sony/Olympus/Pentax for just such a strategic decision when you give them a red demerit for not having IS on a lens in a lens review?
Isn't that a breach of the principle you just noted?
As well as being misleading to the tyro reader who may be unaware that the red demerit won't really affect him because Pentax has in-body stabilisation?
--
-adrian charles-
barbados.
http://www.flickr.com/photos/guttaperk/
Makinations
Veteran Member
When have they done this?
They appear to give a green tint to the ones with IS but they do not appear to give a red tint to ones with out. So it appears to be a pro for those with but not a con for those without.
Or did they give a demerit somewhere for not having IS?
Andrew Westlake
Veteran Member
You're absolutely right, that would be unfairly penalising those manufacturers. Then again, it's not actually our policy to highlight lack of image stabilisation on a lens in red, so it's not an issue. Strange but true.
(For the sake of complete transpacency, early versions of the comparison tables for the 70-200s did use red for the unstabilised lenses, but I changed that fairly quickly following internal discussions and forum feedback.)
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Andy Westlake
dpreview.com/lensreviews
Andrew Westlake
Veteran Member
Yes, but it's not something which is remotely obvious.
The Nyquist line on the chart is positioned at half picture height, and denotes the spatial frequency above which any detail recorded is 'false'. This essentially means that a sensor theoretically can't correctly render a uniformly repeating pattern at this frequency or higher.
However we don't measure lens resolution by looking at repeating line patterns; instead we use a series of slanted edge patterns, and an algorithm which analyses the single transition from black to white on this edge using an oversampling method. This is what allows us to get results above Nyquist.
However, at these frequencies, we're not really measuring lens resolution in isolation any more, as the overall system resolution becomes very strongly affected by the camera's anti-aliasing filter. The text in green in each review is a very brief (quite possibly too brief) attempt to point this out.
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Andy Westlake
dpreview.com/lensreviews
I stand corrected, I guess I noticed the infraction but not the correction. 
I still think that it warrants an footnote of clarification where applicable.
cheers
a.
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-adrian charles-
barbados.
http://www.flickr.com/photos/guttaperk/
I still think that it warrants an footnote of clarification where applicable.
cheers
a.
--
-adrian charles-
barbados.
http://www.flickr.com/photos/guttaperk/
PhotoTraveler
Forum Pro
I was trying to find the nice little diagram that I'm pretty sure was on one of the Sony websites at one time. But I did find a flyer for the KM 7D
http://www.konicaminoltaeurope.com/uploads/media/DYNAX_7D_UK.pdf
Go to page 7 "effective at any focal length"
States right there that is also uses the focusing distance along with the focal length.
I went back to the service manual, I know it's in there, but I remember it being only after tracing back a lot of the wiring diagrams. But just as a follow up, it does show very clearly it having Pitch, Yaw and Slant sensors. Which on other diagrams in the manual talking about them refers to them being Gyros. There is also a "remote sensor" which is not clear what that is. Also it shows a "Hall Sensor" which I assume is hall effect sensor, not clear what it is measuring, if it is measuring the speed of the sensor movement or it's position. The ADI info comes over from the mount/other parts, I'm sure I will find it again but it's coming in from other parts of the camera. Similar for aperture information, FL and so forth.
Still, as mentioned in the linked PDF, the AS system does use the ADI information. If Sony would ever get one unified website with all this info this would be so much easier, I know they have shown more detail on it in the past.
It's just the way things work with the AS/SSS don't see why sony would make a big deal over it. Sony's marketing has been pretty bad, as they completely don't talk about all the little nice things in the camera. Even things like the tilt sensor being used to rotate the screen information when the camera rotates. Few non-A mount users are aware of the KM-Sony bodies doing this. But it's never marketed, because it's a small thing that just works like it should. I had thought it was normal until a recent post in the nikon forum that explained the nikons don't do this.
http://www.konicaminoltaeurope.com/uploads/media/DYNAX_7D_UK.pdf
Go to page 7 "effective at any focal length"
States right there that is also uses the focusing distance along with the focal length.
I went back to the service manual, I know it's in there, but I remember it being only after tracing back a lot of the wiring diagrams. But just as a follow up, it does show very clearly it having Pitch, Yaw and Slant sensors. Which on other diagrams in the manual talking about them refers to them being Gyros. There is also a "remote sensor" which is not clear what that is. Also it shows a "Hall Sensor" which I assume is hall effect sensor, not clear what it is measuring, if it is measuring the speed of the sensor movement or it's position. The ADI info comes over from the mount/other parts, I'm sure I will find it again but it's coming in from other parts of the camera. Similar for aperture information, FL and so forth.
Still, as mentioned in the linked PDF, the AS system does use the ADI information. If Sony would ever get one unified website with all this info this would be so much easier, I know they have shown more detail on it in the past.
It's just the way things work with the AS/SSS don't see why sony would make a big deal over it. Sony's marketing has been pretty bad, as they completely don't talk about all the little nice things in the camera. Even things like the tilt sensor being used to rotate the screen information when the camera rotates. Few non-A mount users are aware of the KM-Sony bodies doing this. But it's never marketed, because it's a small thing that just works like it should. I had thought it was normal until a recent post in the nikon forum that explained the nikons don't do this.
PhotoTraveler
Forum Pro
See my response above with the link to the KM PDF that states ADI is used.
On the extra contacts on the lens. These have been used for multiple things since being added.
The were first used to support xi lenses (power zoom). Later on they are used for SSM support and ADI support. There may be other functions we don't know about.
You really should get the Sony, it's cheap and you can feel confident you are serving the review properly. There is a difference in them, and the possible changes brought on by the ADI support will impact your stabilization test, as been noted for a long time when DPR judges the KM-Sony inbody systems, you guys clearly aren't getting the results users see. So the use of an ADI lens could help your findings.
Also I have to ask, you guys have contacts with Sony, why not just give them a ring and ask what has changed and what they can expect. Tell them you are thinking of just using the minolta and they might just send you a Sony version.
On the extra contacts on the lens. These have been used for multiple things since being added.
The were first used to support xi lenses (power zoom). Later on they are used for SSM support and ADI support. There may be other functions we don't know about.
You really should get the Sony, it's cheap and you can feel confident you are serving the review properly. There is a difference in them, and the possible changes brought on by the ADI support will impact your stabilization test, as been noted for a long time when DPR judges the KM-Sony inbody systems, you guys clearly aren't getting the results users see. So the use of an ADI lens could help your findings.
Also I have to ask, you guys have contacts with Sony, why not just give them a ring and ask what has changed and what they can expect. Tell them you are thinking of just using the minolta and they might just send you a Sony version.
Octane
Veteran Member
Andrew Westlake
Veteran Member
Normally we request lenses from the manufacturers, and we can quite happily do so on this occasion too.
Actually, no decision has been made yet; I've simply suggested we may well use our in-house Minolta.
Again, to reiterate, it's not a final decision. But one point we are certainly interested in is establishing how much further manufacturers can push resolution before these 50/1.4 lenses become limiting in our camera tests, for which we'll continue to use the Minolta to maintain consistency, unless we can find a compelling reason not to.
(On this point, one of the outcomes of our Canon and Nikon 50/1.4 tests is that they clearly have plenty in reserve even with current 12Mp APS-C sensors at the apertures we use for camera tests; the Pentax and Minolta will undoubtably follow suit).
Fair point, and one which which will be factored into our final decision.
Obviously not. But the 50s are different; the optical designs most likely haven't changed, and we have our own reasons for testing the Minolta.
What we will actually do is take a perfectly reasoned approach to this, by establishing what differences there are, if any, and then understanding whether or not they'll affect our test results in any significant fashion.
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Andy Westlake
dpreview.com/lensreviews
Andrew Westlake
Veteran Member
Oh, that's because the correction is a direct result of your original post; please accept belated thanks for pointing it out.I stand corrected, I guess I noticed the infraction but not the
correction.
Fair enough, but we'll have to agree to differ on this one.
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Andy Westlake
dpreview.com/lensreviews
Andrew Westlake
Veteran Member
Interestingly it also states that the aperture setting is used, and I really struggle to understand how that can have any significant effect on IS. So at the moment I'm still counting this as marketing blurb, rather than genuine evidence that distance information has a significant positive impact on IS.
I guess the point here is that if distance info had a genuinely positive effect on IS, it would be really easy to demonstrate, but I've never seen any convincing practical evidence. That doesn't mean there's no effect, but as a professional sceptic (as anyone trained in scientific or technical testing has to be) I want to see experimental evidence, not just claims that it must be true because Minolta said so. If all marketing claims were true, then we could stop testing cameras altogether, as everyone currently shooting 10Mp SLRs could readily substitute them with 15Mp compacts and get better quality.
Again though, power zoom and SSM aren't relevant to this particular discussion.
Naturally we'll be talking to Sony, and may well request their version anyway. But we also want to test the Minolta sample we use in camera reviews, so there are two competing issues.
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Andy Westlake
dpreview.com/lensreviews
Thanks, I appreciate your work in digging this out.
is that it says it also uses the aperture. I can't see the compensation in
any way needing to change because of the aperture. They seem to just
throw anything in to impress on people.
This was from the same company (KM) that wanted us to believe that
antishake could stop the motion of dancers.
kind of shake whose compensation doesn't have any use of focus distance.
So there are no sensors found that seem to measure the translation
that, if known, would be able to use distance info.
why they start to perform worse at shorter ranges. If Sony,
or I should say Konica-Minolta, had solved this, why would they keep
silent about its superiority in this regard over competing systems?
Anyway, if the ADI was doing anything good for the SSS; it should be
possible to demonstrate as I wrote in my previous post.
Just my two oere
Erik from Sweden
Yes, I see it. What damages the credibility of that statement in my eyes
is that it says it also uses the aperture. I can't see the compensation in
any way needing to change because of the aperture. They seem to just
throw anything in to impress on people.
This was from the same company (KM) that wanted us to believe that
antishake could stop the motion of dancers.
That is also interesting. I wonder what the slant sensor measures?
I would interpret that as them measuring angular velocity, which is the
kind of shake whose compensation doesn't have any use of focus distance.
Can't that be an IR sensor for the remote control?
Sounds likely.
So there are no sensors found that seem to measure the translation
that, if known, would be able to use distance info.
Because all other systems seem to only consider angular shake, which is
why they start to perform worse at shorter ranges. If Sony,
or I should say Konica-Minolta, had solved this, why would they keep
silent about its superiority in this regard over competing systems?
Anyway, if the ADI was doing anything good for the SSS; it should be
possible to demonstrate as I wrote in my previous post.
Just my two oere
Erik from Sweden
Chad Marek
Senior Member
--
'Anyway, that’s my view. And it happens to be correct.'
-- Supreme Court Justice Antonin Scalia
(Relax - it's 'sarcasm')
'Anyway, that’s my view. And it happens to be correct.'
-- Supreme Court Justice Antonin Scalia
(Relax - it's 'sarcasm')
Two Truths
Veteran Member
I am not sure if it is relevant but it seems like it is difficult to produce image-stabilised lenses with larger apertures and/or shorter focal lengths.
E.g. Canon has only four lenses that are F2.8 and one that is F2.0, the rest of Canon's image stabilised lenses are all F4.0 or darker.
Only one of the F2.8 lens covers a focal range shorter than 70mm, which is the APS-C cropped 17-55mm F2.8 IS.
Maybe aperture does have something to do with in-lens stabilisation, possibly also in-body stabilisation?
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Stuart / the Two Truths
http://www.flickr.com/photos/two_truths/
http://two-truths.deviantart.com/gallery/
E.g. Canon has only four lenses that are F2.8 and one that is F2.0, the rest of Canon's image stabilised lenses are all F4.0 or darker.
Only one of the F2.8 lens covers a focal range shorter than 70mm, which is the APS-C cropped 17-55mm F2.8 IS.
Maybe aperture does have something to do with in-lens stabilisation, possibly also in-body stabilisation?
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Stuart / the Two Truths
http://www.flickr.com/photos/two_truths/
http://two-truths.deviantart.com/gallery/
Andrew Westlake
Veteran Member
Large apertures, yes; the issue here is that the lens groups which need to be moved can become very large and heavy on fast lenses. Short focal lengths, no; there are quite a few stabilised wideangle zooms on the market (e.g. Nikon 16-85, 18-55, 18-200, and Canon 17-85, 17-55, 18-55, 24-105). The driver here is simply the fact that IS is generally considered to be most useful on longer focal lengths.
Yes, but it's a mechanical design issue with the lens...
..and therefore doesn't apply here.
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Andy Westlake
dpreview.com/lensreviews
PhotoTraveler
Forum Pro
A further follow up, on the aperture stuff. In the A700 diagrams, there is a power diagram that is mostly all Anti-Shake bits (yes, the wiring/block diagrams for the A700 call it Anti-Shake, not SSS, so not much need to guess who was still designing the A700, maybe a few more generations and Sony might get the Minolta folks to think they work for Sony) in those diagrams it has AF rotation detect and Aperture rotation detect and they do link up with the Anti-Shake Control chips, so it very well is putting that stuff into the equation. That or the data is just getting put on a common bus shared by the 2 Anti-Shake control chips (analog chip and a sub-cpu) along with other controllers in the camera.
On the remote sensor, I now found where it shows the signals coming out as being IR_Remote, so yes, it probably is related to the IR control.
On the focus distance, not sure if it means much but see 1 at the bottom of this page.
http://support.sony-europe.com/dime/digistill/alpha/compatibility/lens.aspx?l=en&selBrand=Sony+Camera&selModel=D-SLR+A100&selLens=Sony
Bit cryptic, but if it's just trying to say AS works not as good the closer you get to the object then maybe they begin to use the ADI feature to do some form of correction there and that is where it comes into play.
Maybe if you get both the minolta and sony, you can test the AS on targets at different focus distances and see if things change. Even if some of use don't agree with the results of your current test, it's all relative if your using the same test on the "same" lens. So you very well will see a difference.
On the remote sensor, I now found where it shows the signals coming out as being IR_Remote, so yes, it probably is related to the IR control.
On the focus distance, not sure if it means much but see 1 at the bottom of this page.
http://support.sony-europe.com/dime/digistill/alpha/compatibility/lens.aspx?l=en&selBrand=Sony+Camera&selModel=D-SLR+A100&selLens=Sony
Bit cryptic, but if it's just trying to say AS works not as good the closer you get to the object then maybe they begin to use the ADI feature to do some form of correction there and that is where it comes into play.
Maybe if you get both the minolta and sony, you can test the AS on targets at different focus distances and see if things change. Even if some of use don't agree with the results of your current test, it's all relative if your using the same test on the "same" lens. So you very well will see a difference.
Although this thread ceased to talk about the Sigma lens review long ago, I just want to commend you guys on your ability to both receieve and implement feedback. Also, it's impressive to see that you can stick to your reasoning and justify why your reviews are how they are. And there's something to be said about the amount of tolerance you have for the cries of bias.
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