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Messages - Grummbeerbauer

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16
Lenses / Re: Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 27, 2013, 06:27:30 PM »
To finish the story of my copy of the 18-35: I asked a colleague (semi-pro photographer with lots of experience, not a pixel-peeping gearhead ;) ) to bring his backup 60D for testing. We tried it on both bodies in the same light on different targets at different subject distances and this basically confirmed what I observed on my 7D and on my 450D: At 35mm it is OK at close subject distances, way of at longer subject distances, and off by a mile at 18mm.

BTW: He had his Canon 50 1.4 on the 60D instead of a lens cap, so I tried it on my 7D: Focus was spot on. So it is definitely not an iffy AF on my 7D body.

Since I am not willing to bet on being able to fix these issues with the Sigma dock & software (and spending several hours of my precious free time in the process), the lens is going back to Amazon tomorrow. Since I am not yet willing to totally give up on this lens model, I asked for a replacement. Maybe I have better luck this time.

17
Lenses / Re: Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 27, 2013, 06:16:26 PM »
The width of the confirmation range has no correlation to the accuracy of the VF confirmation since it's the midpoint of that range which is used for DotTune. The width of the range is intentionally padded by camera firmware to make it easier for those who rely on the VF confirmation for manual focusing - a narrower range would make it difficult if not impossible to quickly MF, particularly on lenses with short focus ring throws. Firmware applies padding in equal amounts to both sides of the tightest point of phase detection, thus the midpoint of that range is the apex of focus. On Canon bodies the amount of padding is the same for both AF and MF modes; on Nikon bodies the firmware pads the range by 2x when in MF to further assist those acquiring focus to the dot, which is why the video tells Nikon users to keep the lens in AF mode to assure that the confirmed range fits within the +/- 20 AF tuning range.

Interesting info, thanks for that.
It would be great if one could choose less padding for MF in some custom setting.
While I am spelling out wishes: It would be great if all lenses offered adjustment options like the new Sigma lenses and if it could be done on camera (maybe via USB connection to have the better UI of a desktop application).

And it would be even better if we could just set up camera and test target, type in the measures subject distance, and have the software trigger test shots (one done with CDAF for comparison), adjust AF settings in between, and figure out the optimal AF adjustment settings all by itself.  8)

Of course this can only be done by a camera system manufacturer, not for third party lenses... well, unless Sigma gets in contact with the MagicLantern guys to add their own Sigma auto-AF adjust plugin. If ML can more or less directly access the EF mount contacts to implement Sigma's protocol for doch-2-lens communication in software.


18
Lenses / Re: Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 25, 2013, 05:05:38 PM »
I have the same problem with mine on the 7D and Rebel XT.

Oddly, it's fine on the 5D Mark III.

I presume that with "same problem" you are referring to the general need for different AF adjustments settings?

Interestingly, Roger Cicala at lensrentals.com had a four-part series of articles on autofocus precision, starting with http://www.lensrentals.com/blog/2012/07/autofocus-reality-part-1-center-point-single-shot-accuracy (links to the subsequent articles are at the bottom). Very interesting read in general. In articles 3a and 3b he also found out that newer Canon bodies (from 5DIII onward) if combined with newer lenses focus considerably more accurately than older bodies (including the 7D).
That sort of confirms my own experience:I have never been too satisfied with the AF precision of my 7d anyway, it has always been hit and miss (could of course also be my technique, but what technique can be messed up when setting up the camera on a tripod and point it at a non-moving high contrast target?).

I think I will have to do some shots at daylight this week to see if the type of lighting also plays a role. Although a prime lens like this is of little use if it doesn't AF well in low or artificial resp. mixed light.

19
Lenses / Re: Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 25, 2013, 04:52:23 PM »
In particular, contrast detect AF on the 7D has been shown to lack precision, so as the basis got 'dot tune' I wouldn't rely on it.

Contrast detect AF is not the basis of DotTune. As described in the video, either CDAF or manual focusing can be used, whichever method the photographer finds more convenient and/or accurate.

I used CDAF for initial focus and did some manual fine tuning. In any case, the precision was excellent.

20
Lenses / Re: Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 25, 2013, 04:50:45 PM »
I don't fully believe the 'dot tune' method, I'd recommend FoCal or at least commercial tool like LensAlign.  In particular, contrast detect AF on the 7D has been shown to lack precision, so as the basis got 'dot tune' I wouldn't rely on it.

I am also not fully convinced of the dot tune method... after all, in my case I had a range 20 (from -3 to +16) in which I got a stable focus confirmation... that is half of the AF adjustment range! And that was at 35mm and f1.8, i.e., the narrowest possible DoF with that lens.

Regardless, it's certainly possible for a lens to require a different AFMA at the MFD vs. a reasonable distance away (although 20 units is a big difference!).  Then again, AF issues are Sigma's Achilles' heel. However, you might consider the Sigma Dock (which I'd assume is compatible with this lens, but I haven't checked). 

I am indeed about two clicks away from ordering the USB dock, because I would really want this lens to work for me. Seems that for this lens, the Sigma software allows adjustments at 18, 24, 28 and 35mm and for subject distances of 0.28m, 0.35m, 0.5m and infinity, see the screenshot in the DPReview here http://www.dpreview.com/articles/4406844237/sigma-usb-dock-quick-review/2.

21
Lenses / Frontfocusing Sigma 18-35 1.8 on 7D
« on: August 25, 2013, 01:30:01 PM »
Hi all,

I currently have an EOS 7D with a number of lenses, mainly Canon mid-range stuff (24-105L IS, 70-200L F4 IS, 17-55 2.8 IS, 100L 2.8 IS Macro, 85 1.8 ) and two Sigmas (30 1.4 EX (i.e., the old one), and the 10-20 3.5-5.6 EX).
I had always wanted a short FL prime lens which ended me up with the Sigma 30 1.4, but its lousy AF (both regarding precision and consistency) and soft images below f2.0 make me use it only on rare occasions where I can live with a low number of keepers.

I had been eying the new 18-35 1.8 since it was announced, even more so when the first rave reviews came in. Prime like quality and aperture in a zoom, simply amazing. Getting what basically seems to be a "variable FL prime lens" ;) I pulled the trigger when there was a good deal on Amazon recently (710€).

When it arrived, I was thrilled by the lens' haptics and feeling for quality, which is better than any of the Canon L lenses I own and just light years away from the Sigma 30 1.4 EX with its delicate "crinkle" finish and scratchy AF ring.

Focal-length-wise, while the 18-35 is definitely not an "always on lens", I found it to be very useful for a variety of situations.

I had no intentions to shoot any test charts, so I started testing it mainly indoors in mixed light with mainly static real-life subjects, which is my primary use case for such a lens. To my great disappointment, this particular copy on my particular body appears to exhibit a considerable frontfocus. So I printed an autofocus test chart (the one found at http://www.klein-bild.de/focus.htm ) and did some test shots at 35mm and varying subject distances. I always set focus back to MFD or infinity before autofocusing again and did three test shots at each distance and AF adjustment setting. For each subject distance, I concluded the series with a shot focused manually with live view for comparison. 
The good news is that different from my 30 1.4 EX, autofocus was very consistent. But that's where the good news ended already.

It turned out that both at around 1 meter and at 0.5 meter subject distance, I needed to dial in a whooping +20 to get about the same level of sharpness that I got from MF (see screenshots below, the legend is in German, "Motivabstand" meaning "subject distance"). While I would not like the idea of having to do such a huge adjustment, I guess I could live with that.
However, at 0.35 meter subject distance, I got the best results at an adjustment setting somewhere between 0 to 10. That meant that at the +20 setting that I would need for the longer subject distances, I would be in the "barely acceptable" range of sharpness. Anyway, at that point it became pretty clear that even for a single  focal length, the single adjustment value my body offers me would not suffice.
Being tired of test shots for the moment, I then did some additional research and found the "dot tune" focus adjustment method (check out this video: DotTune: Autofocus fine tuning in under 5 minutes ), which seemed to make a lot of sense and promises much faster adjustments and does not require taking hundreds of test shots.
I tried it out at 35mm and 1,75m subject distance (as recommended for dot tune, 50 times FL). I found the range where I got a stable focus confirm to be between -3 and +16, which would indicate a correction setting of +6 or +7.
The big surprise was at 18mm and 0,9m subject, the range of stable focus confirmation only started (!) at a correction value of +17.
I could visually confirm both correction values with actual test shots.
A quick test on my trusty 450D basically confirmed the results on the 7D: Considerable front focus at 35mm which gets better at shorter subject distance, and a plain massive front focus at 18mm.

tl;dr

I found that the Sigma's AF is consistent at a certain focal length and subject distance, but would require different correction values for different FL/SD combinations. This gives me some hope that I could fix it with the Sigma USB Dock and some patience, but I am just not sure if I am willing to accept this.

So what should I do?
Keep it and get the USB dock? I have a week before my "no questions asked" return period expires.
Or send it back for good?
Any comments or similar experiences welcome.

Regards

Grummbeerbauer


22
EOS-M / Re: Some EOS M Information [CR1]
« on: August 20, 2013, 10:46:50 AM »
I think if Canon put the 70D sensor into the next EOS M camera (a quite obvious move, wouldn't it?) that could quickly turn the M system from the being the EVIL system with the worst AF speed (although the recent firmware upgrade seems to have mitigated that issue at least to some degree...) to becoming market leader - in particular for tracking moving objects, where a purely contrast-detection based AF system has a serious conceptual disadvantage.
If they get this to market, I might seriously consider adding an EOS M2 (or whatever the call it) as a backup body to my 7D.

23
Sigma has definitely stepped up their game recently.
I am currently on the fence to buy the 18-35 1.8, what holds me back is the hope for some further price drops when the early adopters have been fed.

The 120-300 2.8 OS is definitely something I would love to have, both for focal length (my longest serious lens is the 70-200 F4 IS, not counting the Tamron 28-300 VC, which has been setting on the shelf for a while now... ;)) and for speed, but unfortunately at 3+kg it is a tad too heavy and at 3k€ also too pricey for a hobbyist.

What really is missing is a serious contender for the Canon 100-400, i.e., a moderate zoom-range, only a f5.6 aperture at the long end, but weight < 1500 grams and price <1500€. And of course this lens should continue the trend of Sigma's latest offerings - awesome image quality already wide open. :)
Neither the old 120-400 OS, the 150-500 OS, nor the 50-500 OS are good enough in my book to seriously challenge the ancient Canon 100-400. If Canon finally announces a successor, it will probably be 20% better and cost twice as much, which finally moves it out of my hobbyist budget. That will definitely leave a huge gap for Sigma to fill.

24
EOS Bodies / Re: EOS 7D Mark II Test Camera [CR1]
« on: March 29, 2013, 08:39:13 AM »
I hope the new APS-C sensors are good. Loved everything about the 7D apart form the IQ was very disappointed. Even if you look on DXO compare it to a 40D there is barely any difference.
I am personally not even that happy with the 7D's AF (after all the praise it received, I had just expected more precision and better tracking), but I fully agree that the high ISO performance of the sensor was not too hot even 3+ years ago. ISO 1600 is barely acceptable, ISO 3200 for emergencies at best.
With the 5DIII being to expensive for an amateur, the 6D being underwhelming, I was really hoping for the 7DII although I had preferred to go FF, but at the added cost of replacing at least 3 lenses, I guess I can live with APS-C.
So if the 7DII turns out to be about that, I might finally sell my two Canon bodies, 6 Canon lenses, 3 third party lenses, and accessories and get a D600 with 24-70 (the Tamron looks great, BTW), 70-200 2.8, a third party macro and WA lens, and take the rest of the revenue and put it into some other hobby.

25
EOS Bodies / Re: EOS 7D Mark II Test Camera [CR1]
« on: March 29, 2013, 08:30:04 AM »
"Viewfinder LCD Higher Resolution Than 7D"

That and the 19-point AF give this away as being purely fictional...
Absolutely agree, that line caught my eye and it simply makes no sense for that type of "fixed-shape", non-pixel-based LCDs.

26
EOS Bodies / Re: EOS 7D Mark II Test Camera [CR1]
« on: March 29, 2013, 08:27:14 AM »
I agree with what many already posted, that would be disappointing for a 7DII -- no dual card slots, no better AF (I have a 7D, and I am not satisfied with its AF for fast moving action, but that could also be a lack of skill on my side  ;)).

At the same time, it is way overspeced for a 70D (10fps, weather sealing etc.)

So if this really to be the 7DII, the only reason that could make me buy it is that is has a significant improvement in sensor performance (RAW!, not JPEG... I do not need better in-camera NR, LR will always be better at that), and that it stays in a reasonable price range (i.e., a good deal below the 6D, 1500€ at most).

But neither do I think that Canon made some miraculous leap in sensor technology, that somehow didn't make it in their recent FF offerings, but now happens to be available for some APS-C camera, nor do I believe that Canon will suddenly return to reason in terms of their pricing policy.

One line somewhat caught my eye, though:

"Viewfinder LCD Higher Resolution Than 7D"
The 7D's viewfinder LCD consists of discretely etched, "shaped" elements. The grid lines, AF points, digits etc. are not created of pixels, but are more comparable to the display of, e.g., an LCD wrist watch. So a statement like "higher resolution" IMO makes little sense - so little, that it could easily discredit this entire CR1 rumor to be utter BS.
The only reason (aside from a 7DII getting a EVF instead of an OVF) that this could make some sense is that they now have a pixel matrix in some areas of the viewfinder to be more flexible with regards to the info they display.

27
Third Party Manufacturers / Re: Sigma Announces New 30mm f/1.4 for APS-C
« on: January 30, 2013, 02:46:15 AM »
I have the current Sigma 30 1.4. Bokeh is nice, however, it is a bit "dreamy" wide open, but gets quite sharp in the center at around f1.8. What bugs me the most though, and is the reason why I don't use it that much is the crappy AF... its more like a lottery.
When Sigma announced the FF 35 1.4, and everyone started raving about the great IQ and AF accuracy,
I decided for me that I will sell the 30mm on medium-term and get the 35 once the latter's price goes down a bit more. While this would probably cost me ~500€, it would hopefully give me a lens that I actually use and at the same time make my lens collection just a bit more FF capable, in case I ever pick up a 5DIII, 6D etc.

Now Sigma announces the revised APS-C-only 30mm... aside from fearing for the resale value of my old sample (which probably ain't too great anyway  ;), but which I hoped would ease the pain of buying the 35mm at least somewhat), I think I will still stick with my original plan: Unless the new 30mm turns out to be at least as good or even better than the 35 regarding both AF and IQ and is significantly cheaper, I see no reason to not go for the 35.
What do you think?

28
At first, I was skeptical about the possible quality of such a solution. But so was Roger, the Lensrentals guy.
Read his take on the Metabones adapter:

http://www.lensrentals.com/blog/2013/01/metabones-magic

Looks pretty damned good to me. :-)

29
Lenses / Re: Canon 85mm f/1.8 vs Other L and non-L Canon Primes
« on: January 14, 2013, 03:44:09 AM »
I have the 85 1.8 and the 100L on a 7D. I found that on crop, 100mm is definitely too long for indoor portraits, while 85mm fits quite nicely (although you will still get problems in tight places). So for me on crop, it was never the question to get the 100 2.0 over the 85 1.8, despite the 100 being better (I heard the 100 2.0 has much less purple fringing than the 85 1.8 on high contrast edges, which is IMO the most critical issue with this lens, but I can live with it since the images are just astonishing in virtually every other aspect).
So on crop: 85 1.8 for portraits, 100L for macros, but the latter -- at least for me -- does NOT double as a portrait lens.
I think on FF, the game is a different one. If you are interested in macro, you might be able to do with only the 100L, although 2.8 max. aperture could be a bit limiting. If you don't need macro anyway, I would probably prefer the 100 2.0 over the 85 1.8 due to the latter's aforementioned PF issue.

About the 85L: A colleague of mine recently got one, and I had the opportunity to play around with it, too. Impressive piece of glass, but extremely sluggish AF (and -- being warned that its AF is slow, I didn't expect much, but I still got a negative surprise here). I guess my hit rate wide open would not be good enough, and if I have to stop down anyway, why should one deal with the extra expense and weight?
We both concluded that it is more of a "show off" lens, and back to the store it went.

30
I' also a happy owner of both the 100L and the 24-105L, and I, too, was thinking "What the ..." when Canon announced the new 24-70 f4 L IS. Way too expensive for little gain.
lensrentals.com has an interesting comparison of 24-70 2.8 I, 24-70 2.8 II, Tamron 24-70 2.8 VC, 24-70 f4 IS, and 24-105 f4 IS, and that averaged over many samples. Here the new 24-70 f4 IS beats the 24-105 by a small margin in sharpness (and by a large margin in distortion ;)), and the Tamron lies in between the Canon 2.8s.

See for yourself:

http://www.lensrentals.com/blog/2013/01/canon-24-70-f4-is-resolution-tests

Still, not only based on that numbers, I don't think that I would ever "upgrade" to the 24-70 f4. I would rather spent that money on the Tamron, which seems to be excellent, given the price.

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