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Messages - neuroanatomist

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Focal length itself does not mean anything.

Focal length combined with sensor size (diagonal) determines the angle of view. Angle of view determines "telephoto compression"

So, 135mm on APS-C (1.6x) and 216mm on FF will give you the exact same "telephoto compression".

'Telephoto compression' and 'wide angle distortion' are aspects of perspective – the apparent size and distance relationships between objects in 3D space when projected onto a 2D medium.  Perspective is determined solely by distance to subject – focal length, sensor size and AoV are irrelevant. 

So your example happens to be correct, but the reasoning is not. 

Animal Kingdom / Re: Red squirrels
« on: December 17, 2014, 10:12:12 PM »
...... you can't make a bird feeder flying squirrel proof....

Too true...

Animal Kingdom / Re: Red squirrels
« on: December 17, 2014, 08:48:52 PM »
those are really nice shots, the red squirrels we have here in the u.s. don't have those comical ears. they look more annoyed than suprised but they are still entertaining to shoot.

I had this ( posted last year. I was also guessing about the long tufts then in March, but in discussing it we came to the conclusion that it's part of the winter coat.

From the linked thread:

... a Red squirrel (Sciurus vulgaris)

The American red squirrel is a different genus and species: Tamiasciurus hudsonicus.  I haven't seen ear tufts like that here, in any season.

Animal Kingdom / Re: Red squirrels
« on: December 17, 2014, 08:32:30 PM »
"More Than I Can Chew"

EOS 7D, EF 100-400mm f/4.5-5.6L IS USM @ 400mm, 1/1000 s, f/6.3, ISO 3200

Lenses / Re: Canon lens firmware update.
« on: December 17, 2014, 12:25:31 PM »
Ineed, but unless I'm mistaken, Canon have not released user-downloadable firmware updates for any of their premium L lenses, whether they will in the future is another matter.

There's really not enough for a precedent.  Only 5 lens firmware updates have come out, one for a $150 consumer lens and the other four for supertele lenses >$7000.  But relatively speaking there aren't that many 300-600 MkII lenses out there, and there were even fewer at the time of the update (my 600 II came with the updated firmware, about a month after the advisory was issued).  OTOH, there are a lot of 24-70/2.8L II lenses out there, representing a major burden on the service centers and a substantial outlay for shipping costs – I highly doubt they'd require sending the lens in.

EOS Bodies / Re: High Megapixel Camera Coming in 2015 [CR3]
« on: December 17, 2014, 08:02:10 AM »
I bet on it being a Canon sensor.  My guess is it will have the 5DIII AF System, and probably less than 4 fps. 

Lenses / Re: Canon lens firmware update.
« on: December 17, 2014, 07:34:58 AM »
Similar thread:

It appears that if there was a firmware update, there'd be an abvisory note and you'd have to take it to a Canon service centre.

That thread precedes the user-downloadable update for the 40/2.8 STM pancake lens.  A camera released 2012 or later (including the most recent Rebel) can apply the update to the attached lens.  Even after that, there was a firmware update for some supertele lenses that required them to be sent in to a service center (but similarly, I can update the firmware on my 1D X myself, but a 1D C must be sent in).  I expect that if a firmware update for the 24-70 II is issued, users will be able to download and apply it themselves.

And the image which started yet another DRone debate could have easily been shot on a Canon.

That's really the point.  No one denies that with extreme exposure pushes, the Exmor sensors are better.  But the 'proof' is usually contrived examples, and in real-world shooting the difference between Canon and SoNikon sensors is often not evident (because scene DR is within Canon's range, exceeds Exmor's range, or the photographer actually wants – gasp! – some blown highlights or shadows that are actually dark in the image).

EOS Bodies - For Stills / Re: Vertical curtain velocity
« on: December 17, 2014, 06:37:18 AM »
The amount of light reaching the sensor is the same as shutter would have been fully opened for a very short time, e. g. 1/8000 s.

At fast shutter speeds with a focal plane shutter, the shutter is never 'fully opened'.  Instead, the second curtain starts moving before the first curtain completes its traverse, so in effect there's a 'moving window' between the curtains – that window gets narrower as shutter speeds get higher.  The fastest shutter speed at which the sensor is fully exposed (first curtain finishes before second curtain starts) is the camera's Xsync speed – the flash duration very short, so the whole sensor must be exposed when the flash fires.  From that, you can tell that the 6D (1/180 s Xsync) moves slower than the 5DIII (1/200 s) which is slower than the 1D X (1/250 s).  Crop sensor can cameras have higher Xsync because the distance the curtains travel is less (1/250 s for 7DII, 1/300 s for 1DIV).

Lenses / Re: 400mm DO II
« on: December 17, 2014, 12:15:51 AM »
Agreed - he had a couple of hands-on minutes with the lens at a trade show, I wouldn't say he 'reviewed a preproduction copy'.   Actually, the fact that he doesn't (get to) review prerelease Canon gear, but rather buys it retail, adds to his credibility.

Speedlites, Printers, Accessories / Re: Lighting setup for studio portraits
« on: December 17, 2014, 12:11:45 AM »
I find that a single 600EX struggles in a double-diffused modifier >600 in2.  They're fine in a 24" softbox, 48x12" stripbox, or 30" octabox.  I often use a single monolight (PCB Einstein) in a large modifier like a 4' octa as key, with 600's in softboxes as fill or kicker, or just with a Honl Speed Grid as a hair/rim light.  I started with PocketWizard triggers, but I've found that using an ST-E3 on camera to trigger the 600's and the optical slave capability of the monolight is quite reliable.

Lenses / Re: What the heck are Perceptual MegaPixels?
« on: December 16, 2014, 08:07:50 PM »
Their P-Mpix value is basically Subjective Quality Factor (hint: Google hook) normalized to the MP count of the sensor.

Besides RRS and Kirk, 4th Generation (they make the Mongoose line of gimbal heads) and Jobu are the other makers of high quality replacement feet that I'd trust.

EOS Bodies - For Stills / Re: Question about our new 7D please
« on: December 16, 2014, 05:47:28 PM »
If there's a (G) version, there's also an (N) version for sale in markets where GPS is prohibited.

EOS Bodies - For Stills / Re: Question about our new 7D please
« on: December 16, 2014, 06:43:35 AM »
G = GPS.  The 6D is WG (wifi + GPS).  Models with wireless/GPS features can't be sold in some places.

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