April 25, 2014, 12:07:03 AM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - BLFPhoto

Pages: [1] 2 3 4
1

Regardless, the real issue is this is n=1 lens.

On this we are in 100% agreement.

Let me also be very clear that I'm not questioning his honesty or integrity.  Rather, in my line of work, I don't accept anyone's work without seeing the data to back up the conclusions.  Otherwise people get dead.  Now we're not risking bodily injury here, even though these new 50s aren't our dad's old compact, lightweight primes.   But we are talking about a serious knock on a new product that seems somewhat out of character with the current paradigm.  If I were Sigma,  and I was looking to build on my newly improving reputation, I would not let a lens anywhere near the street that was such a laggard in focus precision, especially on current flagship cameras of the big OEM players.  Certainly I would not release it with the fanfare this lens is getting.  I'd slap a Quantaray silkscreen on that puppy and let it die a death in kit lens hell. 

Me?  I'm just thinking I'd love to dig in on the at sample shoot and do some root cause analysis.  I guess that's the engineer and test geek in me, though. 

2
The best we lay testers can do is automated testing using products like FoCal.  The tool allows you to not only perform repeatable cycles of testing, but allows you to specify variables such as how the lens is de focused between shots.  Multiple test runs, altering the variables can help pinpoint possible performance limitations or at least give you further insight into the character of your copy of a particular lens.  Over time you can also compare results to note changes or anomalies in the performance that may indicate a need to travel back to the manufacturer for service.  One of the key parameter settings for Focal is for mirror lock up, probably alleviating your need for a wired release to control vibrations. 

I have no experience yet with the LensCal product.  Maybe someone has a comparison. 

3
Here's the thing, Neuro...I would call that 10 shot sample a REALLY shitty result for Sigma.  Worse than many of their older lens' results.  And you're buying that without questioning the validity of the test and data?  I have lurked longer than I've posted, and frankly, I've come to expect more rigor from your responses.  You've got a great academic take on things, and a lot of insight that the more casual Canon user doesn't have, so I'm a bit perplexed here.  Please spare us the harping on precision vs accuracy.  Clearly those of us carrying on the discussion have demonstrated that we are aware of the difference.  I once wrote a defense white paper on the different test methods and protocols required to measure accuracy vs precision.  I'm pretty read into the difference.  I'm also well versed in the absolute test control and statistical requirements to actually assess levels of precision.  I simply don't see that in this review or write up.  It certainly wouldn't stand up to peer review of the test results. 

Therefore, I'm not satisfied that this is a valid result, let alone indicative of the general quality of the lens.  I have followed TDP for a very long time and agree his reviews and methods are some of the most complete out there...the standard. Y which most are judged, as you note.  But here and on other reviews, I think there is a need for much further disclosure of the exact configurations under test, including all camera settings.  Clearly there is room for a lot of speculation on why he got this sequence of shots, and not all of it is to Sigma's detriment.  Incomplete data can be worse than no data if errors are induced in the analysis.

If the Sigma proves to be a lemon, so be it.  But I'm not hanging my hat on that appellation based on this review.  Let's not get too sold on the strong TDP review brand that were blind to gaping holes in the data.  Question everything.  Over on my triathlon forums where we debate aerodynamics and friction to the same degree we here on the canon forum disect lenses, I have a friend who often states, "In god we trust.  All others must bring data."  I'm not a god guy, but I understand what he's getting at. 

Meanwhile, I'm curious to watch the development of more Art series lenses like the 24..

4
No.  I don't think that.  I think there is not enough information to adequately assess the results and pronounce the lens inconsistent as a rule of thumb.

5
Exactly.  Without a reference point, it's hard to say what shots are more indicative of the specific sample's ability to focus.  And the delta could be a clue to some symptom or reason for the lack of consistency. 

One thing I didn't note yet was that few details are given of the specific setup of the AF, including all AF-related CF settings.   Without that information, interpreting the results effectively is problematic at best.

It could very well be the case that certain configurations of AF, for certain bodies or AF modules, give problematic results for these 3rd party lenses, for the well-noted reason that the AF algorithms are developed from reverse engineering.  The issue could be local to that specific configuration and not a global issue, and the lens could therefore otherwise perform admirably.  Should we throw out the baby with the bath water in that case? 






6
... I jumped the gun on dismissing the 6d... And in retrospect I have a good deal of esteem for the 6d...

I can attest that the 6D and it's AF got a mostly ill-deserved drubbing.  While it is true that it's AF sophistication lacks significantly relative to the 1DX/5DMkIII, it is really a better system than the 5DMk II's.  This last weekend I ended up shooting my 6D for a portion of triathlon coverage where I was shooting wide angle on the bikes, with flash.  I used both single shot and Ai Servo as well as both center and other AF points.  In the application I used it, the 6D was more than adequate to the task and I did not feel I would have done better on those particular shots with either the 1DIV or 5DMkIII, which were mounted w/telephotos. 

There are some well noted limitations of the 6D AF due to AF point spacing, and the sensitivity, orientation, and number of non-center points.  Not everyone has multiple bodies to address different shooting conditions and needs and might find a 6D just that little bit short for their needs.  But after a couple of months of shooting and studying the 6D's AF, I have no issues with it when used in appropriate applications, including some that other forum pundits would swear are outside it's service mission.

But if Canon wants to step up the AF in a follow-on model, I won't argue! 

7
What does AFMA have to do with it?  It has to do with controlling variables in a test environment to ensure the results you are receiving.  And despite your protestations, there is an element of accuracy from AFMA related to the precision.  We have no way of knowing which of the sample 10 photos is most representative of the most optimum focus his particular camera and lens combination is capable of producing.  I can also provide you with test results .pdfs where a non or mis-calibrated lens performed more poorly on the focus consistency tests than it did once properly calibrated (AFMA).  That is contrary to the idea that accuracy is unconnected to precision in this application. 

I don't know the algorithms involved, so I cannot hypothesize to any degree of accuracy why that might happen.  But it does...often enough to convince me there is something to it.

And I have to wonder if you read my post completely.  I mentioned my experience in your vaunted "real world" conditions that not only refutes, at least in the 35mm's case, any sort of worrisome AF consistency issues, but that also corroborates what I saw in much more controlled test conditions shooting those pesky test charts. 

What you're calling "real world scenarios" is what we call in my line of work "operational testing".  Beware that all "real world scenarios" or "operational testing" is not equal for purposes of drawing conclusions from them.  Test design and controls have a lot to do with the fidelity of data produced.   And I'm saying given the paucity of information regarding test controls on TDP's "real world" shooting, we cannot faithfully put much stock in an idea that this 50mm indeed has any AF issues worth worrying about. 

I'm not trying to defend Sigma, per se.   I'll dump the Sigmas in a heart beat if the evidence gives me reason to doubt their performance.  But I'm similarly not going to simply buy some anecdotal "evidence" as proof without ensuring the evidence is properly controlled to produce the results noted.  In this case, the most glaring control missing is sample size.  I believe TDP did some fairly exhaustive shooting, probably using fairly common tools, including tripod when necessary.  But the results are based on a sample size of 1 lens, which is not adequate to properly draw conclusions from.  It's not good enough to dress up a review and AF performance test with accounts of how much and how varied the conditions were that produced the results, even if I grant you 2 test configurations based on his mention of testing both 1DX and 5DMkIII bodies with the lens.  Not for me, anyway.  I need more data.

8
While not knowing your financial situation, I can recommend keeping the 40mm.  It works well as compact body cap that still has your camera in a ready-condition.  Additionally, you may always find situations where you don't want to risk your nice 35mm to the elements you're shooting in.  Far better to risk a $150 lens in those instances.  Not to mention that it is relatively similar to the 35 and 50 focal lengths to serve as a useful backup in case the unthinkable happens to your primary lenses.  Similar to why I kept my Mk I 50mm f/1.8 loooooong after I got the 50mm f/1.4, and still keep it despite also owning the 40mm.  They were cheap investments and easy to justify keeping around for those "oh crap" situations.   I got my 40mm for $130 open-box from Best Buy when I wandered past their photo cabinet on my way to get a TV.  I instantly loved it, despite the fact that I really prefer the 35mm focal length as a matter of choice in shooting.

I have a whole litter of lenses, but the one that is on the camera I always have near me "just-in-case" is the 40mm.  Small, unobtrusive, and more than capable of capturing fleeting moments in most documentary situations.  The 40mm, a 6D, and a 580EX II now form the cornerstone of my lightweight running photography pack.  Sometimes I go out with nothing but that setup and the 135L in my bag when I'm cycling or running with a group or for long treks away from roads during ultra marathons, etc..  Carrying the 24-70 zoom or even one of my 35 1.4s would significantly impact my range given pack space, weight, and food considerations. 

Your situations may not be similar, but consider those situations in your own photography where being light, small, and unobtrusive would be a plus.  Not every situation requires IS or the best IQ you have available in your kit at or near a given focal length. 

It's a cheap investment that you've already made.   

9
I don't know how TDP conducted the test other than the layman's description that he posted, but I'm highly skeptical that there are serious issues with the AF.  First, we know nothing of the pre-configuration of the lens and/or camera system.  Was it properly calibrated for AFMA?  Was it calibrated and checked with the Sigma dock?  I would not draw any conclusion about any lens, OEM or otherwise, for which I didn't do some basic configuration and calibration with my equipment that it is interfacing with. 

We also know little of the lighting conditions under which the photos were taken. 

I'm not doubting a reasonable effort to see what would happen when the lens was mounted on a camera body.  He does decent work.  But these results are more anecdotal than any serious evidence of a focusing issue.  The 35 1.4 was initially reported to have issues as well.  But those simply aren't bearing out in reality.  I can report having run my own Sigma 35 1.4 as well as two from local friends through the full gamut of Reikan FoCal calibration and performance tests.  These were run on multiple bodies, both my own and others.  Focus consistency for all three of these Sigma 35 1.4 copies always measured in the 97-98% range for all bodies which had AFMA available and which was performed.  For reference, all three of the Sigmas tested more consistent than my own Canon 35mm 1.4.  Aperture sharpness curve was superior to my Canon on all three copies.  Focal point consistency was equivalent between the Sigmas and my Canon.  In short, I see no evidence of a shortfall in AF performance on the Sigma 35 1.4 compared to my Canon version based on empirical evidence on fairly well-controlled tests given the sample community I have access to test.  And my experience in shooting my Sigma 35 1.4 in the real world bears these "lab" tests out.    I have had zero focusing issues in any conditions that were notably different from anything I experience with the Canon version on a given body. 

Part of my day job is engineering developmental and operational test and evaluation design and execution.  There is far more involved in properly testing an item than most people give credit for.  I trust what Roger at LensRentals says about lenses more than most any others out there.  He has a vested, financial interest in establishing a watertight, repeatable test protocol for the thousands of lenses they own.  They have invested in the right kinds of equipment and established clearly repeatable conditions under which to evaluate lenses.  If Roger, at some point, comes out with an AF performance delta between the Sigmas and their Canon counterparts, I would be inclined to then hang my hat on that.  Certainly it will be based upon a test sample far larger than anything we, TDP, DPReview, or others might have access to. 

I am not hesitating one bit to invest in this new Sigma 50mm 1.4. 

My only concern with these new Sigmas is longevity.  Will they still maintain their performance after a decade or more of service?  My Canon 35 1.4 is far more than a decade old in my hands and has given not a single hiccup.  It has been cleaned and serviced by Canon once during that period.  Are these Sigmas constructed and capable of the same level of reliability?  I don't know.  But I'm going to invest in the opportunity to find out.  At these prices, both the 35 and 50 Sigmas together cost about the same as a new Canon 35 1.4 alone.  Seems like a reasonable risk proposition to me.  And I'm known in my day job as risk-averse!


Edit:  Oh, and when they come out with this 24 1.4...sign me up. 

And, full disclosure, I did own Sigma's newest 70-200 f/2.8 OS briefly as a replacement to my aging old Canon 80-200 f/2.8L.  I quickly rejected it after a few months specifically for sub-par focus consistency and distracting bokeh, particularly with a 1.4x teleconverter.  The Canon 70-200 f/2.8L IS II I have now is so much better as to be in a completely different league.  All of which is to say that I'm not unfamiliar with Sigma products AF issues and unfavorable performance relative to similar Canon products.  I am simply astounded on what I've found with the 35 1.4 so far.  So much so that it has right of way in my bag at the moment.


10
Lenses / Re: Wait for Sigma 50mm Art or purchase Canon 135 f2L.
« on: April 08, 2014, 10:09:40 PM »
I've had my Canon 50mm f/1.4 for nearly as long as I've had EOS cameras...19 or 20 years.  The only lens I've had longer is the original 50mm f/1.8 mk I with the metal mount.  I loved it(the 1.4)...until I didn't.  And that was starting about with the 40D.  It was still good on the 5Dc, though mine probably suffered from the lack of AFMA on early digital bodies.  Now I mainly use it for detail shots and street shooting from f/4-f/8.  It still shines in that mode.  But I love the focal length for composition and really want a great 50 1.4.  I never liked the focus shift on Canon's 50 L, so that lens is not on my list. 

Hoping the 50 Art is as good as anticipated and as good as the 35 Art that I already have. 


11
Lenses / Re: Wait for Sigma 50mm Art or purchase Canon 135 f2L.
« on: April 08, 2014, 03:00:37 PM »
For my $, you already have the 50mm range covered with the 24-70 f/2.8 and even the 35 f/1.4.  But the 70-200 f/4 leaves you with a slower medium telephoto.  So I would go with the 135 f/2L.  I have had mine for nearly as long as it has existed and would not give it up.   

As you can see in my signature, I have the Canon prime trinity of 35 f/1.4L, 85 f/1.2L II and 135 f/2L.  I replaced my 85 f/1.8 with the L series only in the last couple of years, so can speak about having used that 1.8 lens with the 35 and 135 Ls for nearly a decade.  I can almost always cover any shoot with those three lenses. 

I had the original 70-200 f/4 non-IS for a while when it first came out, but I found it was often too slow for the more active shooting I do.  I always prefered the 135L when I could get away with that focal length. 

Even now that I also cover that range with the 24-70/70-200 f/2.8 duo, I more often use the primes in most non-sports situations. 

That's a disjointed way of saying go for the 135L now.  You won't regret it, even on APS-C.  It makes a great ~189mm focal length equivalent and the f/2 keeps the shutter speeds up without jacking the ISO. 


12
EOS Bodies / Re: Patent: EF 85mm f/1.2L III and Others
« on: March 31, 2014, 01:21:09 PM »
I love, love, love my 85II for all reasons stated above, but seriously, this lens has really bad LOCA that's difficult to fix in post.

If they found a way to reduce the green/magenta bokeh CA, I would upgrade in a heartbeat (assuming that's even possible on 1.2 lenses)

It is correctable to some degree through use of APO lens designs.  As always, though, there are varying degrees of effectivity even among respective APO designs, and if we REALLY demand the goods...we're probably in Leica territory for price. 

The third party makers (Sigma!) often designate APO on lenses, but while the design may be APO, their particular realization of the design usually leaves much to be desired.  This can be due to any number of design constraints. 

Canon's L-series Flourite coatings are part of their APO equations where used.  However, to the best of my knowledge, the 85mm f/1.2L is not an APO design.  Maybe someone has more or better information than I have, though.

Leica made a 90mm APO lens that will show you what REAL APO can achieve in shorter lenses in the portrait range.  It sold for almost $4k, though.  How badly do you want rid of that LOCA on the Canon 85?  I'm pretty ok with mine! ;-)

13
Correct....the reason Ai-Servo is not guaranteed sharp is that it never stops focusing as long as the AF on is engaged, whether at the shutter button or on the camera back.  If you're shooting motion...you're focused on maintaining your focus point on the subject.  If, on the other hand, you're shooting static, with Ai Servo, you're really trying to use it like One-Shot AF...and but while you held the AF-on engaged, you may have moved off the intended subject point slightly.  And there is the additional confounding factor that Ai Servo is apparently less light sensitive in practice than One-Shot.  More sensitivity to light means more sensitivity to the point of intended focus. 

Nevertheless, Ai Servo works exceedingly well across all of the newest Canon upper range, and is pretty darn good going back to the 7D, 1D Mk III and 1Ds III. 

Reading across many, many photography forums, it becomes plainly evident that many, if not most focusing problems are more related to operator error in misusing or mis-understanding the focus system of their camera and setting it up correctly for the type of shooting being done. 

Two things were clarified to me in the OP, the light sensitivity difference and the logical accuracy difference due to time to acquire focus between the two modes.  I certainly am a bit more informed by this thread. 

14
I own both.  I've written elsewhere of some specific instances where I definitely prefer the 135L to the 70-200L IS II.  Indoor sports is a given to gain back a stop and be able to increase your shutter speed.  If you're using strobe(s) indoors, that advantage is essentially nullified and I'd lean toward the zoom's flexibility. 

One use for which I have a significant preference is when I shoot ultrarunning, mountain biking, or other outdoor sports in close, cluttered background quarters such as tree-lined trails, etc.  The f/2 of the 135L really helps to drop out the background even when it is tough to put distance between the subject and background.  Images between the two lenses, shot both at 135L will clearly show the difference.  I think I posted some examples in a 135L thread.  I prefer the 135L anytime I can get close enough and want to isolate a single athlete or subject.  (The 200 f/2 IS is on my short list and would be even better, but probably not this year).

Shooting wide open, the 135L really does a better job on creating separation.  Of course the 70-200 images are crazy good anyway.  But "everyone" has a 70-200 f/2.8.  If you want to give your images that little extra, the 135L will do it. 

Will you use it a lot?  I can't answer for you because I don't know what your style and subjects are.  For me, they get about equal billing in the sports that I shoot.  For weddings I prefer my 35/85/135 prime trinity almost always.  For general purpose shooting across all types of images you would probably prefer the flexibility of zooms.


15
The antidote for saccharine photography...

http://www.smogranch.com/

http://www.aphotoeditor.com/

Check back when you've meandered through them.  You'll thank me.

Then again, this is a gear rumors site, so back to the pursuit of mechano-electrical photographic perfection...

Pages: [1] 2 3 4