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Messages - neuroanatomist

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Lenses / Re: Teleconverter
« on: March 27, 2013, 10:34:30 AM »
every extra bit of glass will reduce iq

O.k. so I will put my eye glasses down ... asüdü aüfbis fiasbfsl lxc ... no, with eye glasses IQ is better and I see what I am typing!

LOL.  Ok, now put on two pair of glasses.  Is that better than one?

Lenses / Re: New 100-400 to Launch with EOS 7D Mark II [CR2]
« on: March 27, 2013, 09:06:21 AM »
Love my 100-400, would appreciate better IS, full sealing, and optical improvements. If it's as sharp as the 70-300L, awesome.  Hope they keep push-pull, but could learn to live with rotating extension.

Expensive, yes it will be.  But probably worth it.

100-400 F4 without 1.4 extender, Would be a good alternative to the 200-400 maybe half the cost?

Ha ha ha.  100-400mm f/4 means the same front element size as the 200/2, 400/4, 200-400/4, etc.  Would be a $7K lens easy.  Get off this, folks, it'll be f/5.6 at the long end, and likely close to $3K at that.

Lenses / Re: How Much do you use your Canon EF 16-35mm L ??
« on: March 27, 2013, 05:58:55 AM »
And how are you finding it?

Excellent.  :)  Wickedly sharp, great colors and contrast, blazing fast AF, solid build.

Did you sell your 24-105?

No, I didn't.  But if I don't use it, I will...

Lenses / Re: How Much do you use your Canon EF 16-35mm L ??
« on: March 27, 2013, 12:48:51 AM »
And how are you finding it?

Excellent.  :)  Wickedly sharp, great colors and contrast, blazing fast AF, solid build.

Lenses / Re: How Much do you use your Canon EF 16-35mm L ??
« on: March 26, 2013, 11:55:30 PM »
Congrats! Enjoy it when you get it... 

EOS Bodies / Re: 6D Autofocus not impressive
« on: March 26, 2013, 11:48:15 PM »
As you state, the 6D doesn't even have that.  Just sayin'.
As you're the expert on Canon gear: Are there any redeeming reasons for Canon implementing the 5d2 af in the first place and then copying it to the 6d (+2 non-cross points, +low light af)? Maybe designing an af array for ff is more complicated/expensive - even though the af spread on 5d2/6d isn't very large?

Well, first off there was no 'implemented AF' in the 5DII - Canon simply reused the AF sensor from the original 5D.  Many people compare it to the 20D/30D AF, but of course the sizes are different so the design is different. The theory of the assist points was nice - 6 'invisible' points to help with servo tracking. But in practice, it didn't work well, I suspect in part because of a slow AF chip and weak algorithms - and I bet they reused the whole system (AF chip and code) from the 5D in the 5DII, meaning a really old AF system. For sure it couldn't track well, and enabling the assist points (which are off by default) didn't seem to help.  As for why, reusing the 5D's AF saved development and production costs. Similarly, when the 40D got a new AF array, the 20D/30D's system went to the Rebel/xxxD line, and eventually the 40D/50D/60D's AF went to the T4i/650D (which I expect means we'll see something new in the 70D, my money is on 15 points, 9 crosses </speculation>).

The 6D got a similar system, looks like a modification of the basic 5D design. No more assist points (too bad, IMO, because with a modern AF chip and current algorithms, those tightly-clustered points may have been effective.  I'm not sure I buy the bit about needing 'elements of the AF system to be larger' to support -3 EV. AF point size and threshold determine micro lens size, low light is more about signal amplification, and given the density of the 5DIII/1D X AF sensor at -2 EV compared to other bodies at -0.5 EV, I don't see it. 

Why 11 points on the 6D?  I'd say pure marketing. The spread is no greater than the 5DII, just two extra points stuck in there.  But consider the 6D's market position - 'entry-level FF'. Targeted to Rebel/xxxD and xxD users looking to 'go FF'. So, the target upgrade audience all have bodies with 9 AF points (and 18 MP sensors).  So, give them 11 AF points (and 20 MP).  Canon's marketing department understands that for most consumers, quantity trumps quality - the former is a simple 'more is better' and can listed as a top-line spec and be printed on a display placard at Best Buy, the latter requires some technical understanding (e.g., why 9 cross-type points are better than 1 cross type plus 10 lines).  </cynicism>

Lenses / Re: Also chasing Tack Sharp
« on: March 26, 2013, 08:24:28 PM »
I used the 85/1.2 for a couple days once and was underwhelmed by both the focus speed and ca when wide open.

CA's with the 85mm L are extremely low, focus is slower though.  It will be hard to beat the 85L for CA's.  0.14 pixel at f/1.2!  If that's too much for you, you are going to look far and long.

Yeah, but that's lateral CA.  Longitudnal CA is a different matter. Lots of magenta and green there.

Here's a test from a while back, focusing successively on each battery in the first composite, crops of the chrome ball in the second composite.  You can see LoCA showing up green in OOF specular highlights behind the focal plane, and magenta in front of the focal plane. Stopping down reduces the LoCA.  Watch out for those chrome bumpers and water reflections, people.  ;)

Lenses / Re: EF 16-35mm f/2.8L II USM vs EF 17-40mm f/4L USM
« on: March 26, 2013, 08:17:23 PM »
The conventional wisdom is that when stopped down to f/8 or so, there's not much difference between the IQ of the 17-40 and the 16-35 II, the latter costing twice as much. 

Neither lens is particularly good for architecture - both have significant distortion at the wider end. 

Instead, you might consider the TS-E 24mm II or the TS-E 17mm - both are excellent for architecture and landscape, the movements allow you to compensate for keystoning (keeps the vertical lines of buildings straight) and allow very deep DoF without stopping down so far that diffraction costs you sharpness.

I think you would be better off with the 7D, I prefer the AF on the 7D vs the one in the 1d mkiv.
Sounds outrageous but I'm open to surprises and learning ... so do tell us why.

Asked thrice.  Still no response...

EOS Bodies / Re: 6D Autofocus not impressive
« on: March 26, 2013, 07:48:24 PM »
I admit my annoyance with the 6d af means that I might be a bit simplistic - but in fact many people seem to think that the 6d has a xxd-style center cross point (extra sensitive for f2.8 lenses) while with the 6d the opposite is true (non-cross overlay). Then think of the 1dx/5d3 double-cross points - doh.

In fact, xxD bodies since the 40D have been 9 cross-type at f/5.6 with a dual-cross center point (f/2.8 'x' superimposed on the center f/5.6 '+').  Moreover, even the T4i/650D and T5i/700D now have that AF sensor.  The 1D X/ 5DIII have a vertical row of five of those dual-crosses, not just one in the center.  As you state, the 6D doesn't even have that.  Just sayin'.

Lighting / Re: Elinchroms and High Speed Sync
« on: March 26, 2013, 06:37:45 PM »
There are two issues at play here - the latency of your triggering system and the fact that your camera's shutter uses two curtains.  Up to the maximum sync speed, the entire sensor is exposed for the entire duration of the exposure.  Faster than that, the two shutter curtains form a "slit" which "travels" over the sensor - i.e. the entire area of the sensor is not exposed at once.  As a result, only a small area of the sensor will get exposed by a single burst of the flash.  Hence why HSS uses a burst of pulses.

True.  I missed that above, thinking 1/2000 s exposure.  But you're right, 1/2000 s is the instantaneous duration of the area between the curtains (the slit), and that slit takes much longer that 1/2000 s (and longer that 1/1000 s) to traverse the sensor.

The way monolights are used is taking advantage of the 'tail' of the flash duration.  The 'action mode' of the Einsteins purposefully extends that tail (at the cost of constant color temp).

Timing is still key.

Lighting / Re: Elinchroms and High Speed Sync
« on: March 26, 2013, 02:42:41 PM »
In theory, if the timing is optimal, then yes.  That's how the PocketWizard HyperSync works.  The timing will need to be tweaked for each camera/light combo, so your triggering system will need the capability to fine tune the timing.

EOS Bodies - For Stills / Re: 6D Micro adjusting lenses
« on: March 26, 2013, 02:37:06 PM »
It's in the manual, p.314.  It's not an automatic funciton, you have to test the lens+camera combo to determine the amount of AFMA needed, if any.

I'd recommend buying Reikan FoCal. 

Lenses / Re: Canon 24-105 F/4L
« on: March 26, 2013, 03:37:45 AM »
@ TrumpetPower - yes, me.  ;)

Low light shot with an f/4 lens:

EOS 1D X, EF 600mm f/4L IS II, 1/160 s, f/4, ISO 10000

HTP increases the DR if you shoot in JPG.  It underexposes by 1 stop of ISO, then lies about it in the metadata (that's why ISO 200 becomes the lowest setting - if you shoot at ISO 200 with HTP, the camera actually exposes at ISO 100). That 1-stop underexposure preserves a stop of highlights, the camera then applies a tone curve to boost everything but the highlights by 1 stop (meaning a stop more noise in the shadows).

If you shoot RAW, leave HTP off.  You then have latitude to preserve >1-stop of highlights, and can apply your own tone curve.

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