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Topics - 3kramd5

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Third Party Manufacturers / Sigma and Tamron OS/VC quirks
« on: August 22, 2014, 09:35:02 AM »
I now own two third party stabilized lenses, the sigma 70-200 2.8 EX (there are a lot of letters and I always forget them) and the tamron 150-600. I've noticed a quirk they both exhibit that none of my canon IS lenses do: when the stabilizer engages, the frame tilts down what visually feels like about 5-10°. With the 70-200, it's not that bad, but at 600mm with the tamron, 10° is a lot.

Has anyone else noticed that kind of this happening? What's the explanation? Misalignment in the stabilizing optic? Maybe I'll shoot a video if nobody can picture what I'm seeing.

Does anyone know if it's possible to back up personal settings for non 1D-series cameras?

EOS Bodies / dual pixel tech going forward
« on: April 24, 2014, 09:41:13 AM »
On the 70D, canon has two photo-diodes per pixel almost across the entire sensor. The fact that they can get useable phase information from them suggests that they can read them independently.

So, could they change the bayer filter out and double resolution rather than get sensor level phase detection? Perhaps being co-located they couldn't use a traditional bayer design, but could they for example have green AND either red or blue at every pixel?

If so, that could be a cost-effective way forward to producing 1DmkV and 1DmkVs cameras once DPAF is perfected to the point that it equals or betters SIR AF. The former could have a traditional bayer filter with the second processor dedicated to amazing autofocus; the latter could have double the resolution and use a simpler last-gen SIR AF unit.

I am probably fundamentally misunderstanding the implications of having two photo-diodes per pixel, though. More likely DPAF is their way into high end mirrorless.

EOS Bodies - For Video / Understanding Video Autofocus
« on: March 15, 2014, 02:22:03 PM »
I rarely shoot video, but was messing around with it today (5D3). I noticed that, if I try to autofocus in video (and probably live view stills too, but I haven't verified), it gets significantly brighter while achieving focus, even if I'm already shooting wide open. What causes that to happen? Does it momentarily drop the frame rate? Can it be avoided? It looks extremely jarring.


EOS Bodies - For Stills / 5D mk II AF problem
« on: May 30, 2012, 07:37:56 PM »
I think one of my sensors is bad/broken, specifically the lower left. Every other sensor grabs focus pretty quickly in good light. Almost exclusively, the lower left will go to infinity and back before stopping, sometimes in focus, sometimes not.

This is a recent thing; I've used the sensor in the past. Any ideas what could cause it and how to go about fixing it?

EOS Bodies - For Stills / Calculating Dynamic Range
« on: March 12, 2012, 09:52:15 AM »
Rather than hijack any of the existing threads on DR, I thought I'd start a new one.

I'm still struggling a little with the concept by which a few people (LetTheRightLensIn and maybe a couple others) are computing Dynamic Range.

Maybe my understanding of DR itself is faulty.

Is not DR the total range between brightest bright detail and darkest dark detail that a camera is capable of recording in a single exposure?

If so, how does having two separate exposures, one completely underexposed (body cap on stopped down fast shutter) and one completely overexposed (bright, slow shutter) aid in computing maximum potential DR?

Wouldn't you instead need a to meter at the median brightness point in a scene containing a fairly slow transition to complete dark and a fairly slow transition to complete bright (i.e. overexposed white and underexposed black existing together in a single exposure with smooth gradients towards the center) in order to determine useful DR?

I have a technical background, but I'm looking more for conceptual understanding than anything.


So, per the DP review description,

"The 5D Mark III loses out to the Nikon D4 and D800 when it comes to use with slower lenses or long lens/teleconverter combinations, in that its cross-type points can only be used with lenses that are F4 or brighter (and the double-crosses with F2.8 and brighter lenses). Canon says there's a trade-off to be made and that its approach allows the sensor to be more accurate with the large aperture lenses it expects its customers to use, and allows the F4 cross-type sensors to be placed further towards the edge of the frame."

So, the middle AF point (and indeed much of the center column) is double cross type. All points in the center three columns are either cross or double-cross points.

Does that mean that, if I'm using an f/5.6 lens (say 100-400 at max focal length), I would only be able to use points from columns 1, 4, 8 and 11? Or will the higher accuracy points function with less fidelity? Can I not use the center point with my 25-105?

Seems kinda foolish to force focus off center for slower lenses.

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