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Messages - neuroanatomist

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6286
...if this 501 plate system is arca swiss compatible, it sounds like it would be the way to go..?


Sorry, but it's not.  The 501PL and 504PL plates used by the two B&H items you linked are interchangeable (the 504 is a longer version of the 501), but they're compatible only with certain Manfrotto heads.  If you want to convert Manfrotto 501-compatible heads to work with Arca-Swiss plates, you need the Kirk SQRC-501PL ($150).

6287
Reviews / Re: Review - Canon EF 70-200 f/2.8L IS II
« on: January 16, 2013, 12:30:13 PM »
I'm pretty torn between this and the new Tamron 60-200 with VC. True, not bi directional and 4 stop VC but it is black AND 700 dollars less. Haven't found too many articles and comments persuading me to go with Canon...


How about the difference in sharpness at 200mm? They're similar at the short end, but the Tamron 70-200 VC appears significantly worse at the long end.

6288
Speedlites, Printers, Accessories / Re: Depth of Field calculators
« on: January 16, 2013, 11:42:18 AM »
I use the free Field Tools app, works well.  I also use Photo Aide ($2), which does FoV calculations (and others) in addition to DoF. 

6289
Canon General / Re: Why buy from a bricks and mortar store?
« on: January 16, 2013, 10:59:31 AM »
I'm sure our government will close the tax loophole soon enough, but until then, I will do as I need to...

Sorry, but it's not a loophole.  In pretty much every state that charges Sales Tax, there's an equivalent Use Tax that applies to goods purchased out of state for use in the state where you reside.  The buyer is responsible for paying that tax to their state government.  A loophole is a technicality or ambiguity that allows you to avoid the spirit of a law while obeying the letter of that law.  Not paying Use Tax on internet purchases is flat out tax evasion.  Much like driving 10 mph over the posted speed limit, it's unlikely you'll ever be caught/penalized...but it's still against the law.

6290
Reviews / Re: Review - Canon EF 70-200 f/2.8L IS II
« on: January 16, 2013, 10:54:52 AM »
"(technically the front 77mm lens element requires a filter to be fully weather sealed)"

I have always wondered about this.  On this lens and others that make this statement, why make it in a way that needs a filter to make it weather tight?  It's like they worked really hard to make it weather tight until they got to the front and said, oh who cares, lets require a filter. 

How can I be sure my filter is weather tight? How can Canon?

To be honest, I put my gear away when it starts to rain, an I don't run my gear under he faucet to clean it.  I just wonder why they "require a filter".

That statement in the review is not correct.  There are only a few 'sealed' lenses that require a front filter to complete the sealing - the 16-35L I/II, 17-40L, and 50L.  Those lenses have a front group that retracts into the lens barrel with zooming/focusing, and for those lenses, the requirement for a front filter to complete the sealing is clearly stated in the manual for the lens. 

Chuck Westfall has recommended the use of a front filter with all sealed lenses that take one, but he didn't state that it was required.  Basically, a little extra insurance. 

6291
Lenses / Re: Tips needed for shooting in the cold
« on: January 16, 2013, 10:48:47 AM »
Regarding your Carbon Fiber tripod... that should be good down to about -4 degrees F (Induro specification).  Below that it can become more brittle and easier to damage and likely would not be covered under warranty.

I wonder about this - I've read statements like this posted several places, but CF tubing and plating is commonly used on the exterior of deep space vehicles which function near absolute zero (e.g. Voyager 1's main antenna dish is CF).  Maybe it's down to the resin used to bond the carbon fibers into shape?  Most resins are quite cold resistant, and constitute <30% of the tubing material (the rest being carbon).  So I wonder if the 'carbon fiber shatters when it gets too cold' is just an urban myth?

6292
Lenses / Re: Question about variable aperture
« on: January 16, 2013, 10:34:31 AM »
Basically, the virtual aperture for a telephoto lens design is right at (or very slightly behind) the front element.  The real aperture is smaller, but that doesn't matter in terms of element size - it's the virtual aperture that has to be filled with light (for other lens designs, e.g. retrofocus lenses like UWAs, the front elements are apparently much larger than they 'need' to be - it's a different design).  What Chuck is saying is the 70-200/2.8 has a real, physical aperture that approximates 70/2.8 (e.g. ~25mm), and that the elements in front of that physical aperture 'magnify' it to form the virtual aperture, which gets larger as you zoom to longer focal lengths. 

You get a sense of that from the block diagramL


When looking at one of these, though, it's not just the position of the iris diaphragm or the sizes of the elements relative to the approximated size of the iris diaphragm - you also need to consider the elements themselves, whether they're converging or diverging lenses.  Roger Cicala wrote a series on the basic lens designs a while back, on his lensrentals blog (and IIRC, CR reposted here with permission) - worth a read.

6293
Lenses / Re: Question about variable aperture
« on: January 16, 2013, 10:13:50 AM »
Thanks Neuro: Does it mean that the 70-200 mk.ii could possibly do 70mm @ f/0.98 ? (200/2.8 = 71.4, and 70/ 71.4 = 0.98) Since the lens element is large enough?  So the lens potentially could be a Variable 70-200 f/0.98 -2.8L ? If they so chose to build it with similar glass elements?

Chuck Westfall answers that in the link above (the answer is 'no', BTW).

6294
Canon General / Re: Why buy from a bricks and mortar store?
« on: January 16, 2013, 09:54:18 AM »
Sounds like a nice incentive to increase business. 

As we've seen lately, brick-and-mortar stores are suffering - both large chains and small independents.  For the small stores, some of the problem is actually Canon's fault.  According to the owner of a local store (not a chain) I was talking to a few weeks ago, in addition to Canon's recent MAP policy, they also cut margins (i.e., raised wholesale prices), adding back via 'discounts' for volume and for pre-payment, both of which are hard for an independent shop to meet. He said that was pretty much the last straw for him. In fact, that was what brought me in. He was liquidating much of his photo gear and shutting down his print lab, leaving just the broadcast side of his business - essentially B2B with no effort on the consumer end. He said he'll still sell Canon video-oriented dSLR gear (5DIII and up, fast lenses), and he's not expecting a significant profit from those sales.  (He also sells field lenses like the one you posted a partial picture of, and sells the cameras they must be used with...ok, I'm all done beating that horse now  ;) ).   

6295
Lenses / Re: Tips needed for shooting in the cold
« on: January 16, 2013, 09:41:41 AM »
As stated above, batteries don't last long in the cold - have at least two, keep one insude your coat close to your body where it will stay warm.  When you swap them, put the 'drained' one inside your coat - when it warms up, it can be used again.  (Also as stated, I've used a 1D X battery all day in the low 20's, no problem.)

I do put the gear in a plastic bag before going into a heated environment.  I just keep a couple of Space Bags® in the car (big enough for a 600/4), put the gear in there, then take them inside.  After they equilibrate (a couple of hours), I do put them in a Storm hard case with fresh desiccant packs.

Your tripod will be fine, just wipe it dry when you go inside.

6296
Canon General / Re: More Canon Store Information
« on: January 16, 2013, 09:28:06 AM »
Why do you guys keep calling it a store? You can't buy anything from it, and that's why Canon don't call it a store. It seems also to be very hard to "experience" a 1D-X or a 5D3 in one of them. Oh sorry, they're only for CPS guys, they're too expensive for eager beaver amateurs to get their mitts on.

I'd call it a store, because "Experience" sounds pompous and silly.   :P

6297
Reviews / Re: Review - Canon EF 70-200 f/2.8L IS II
« on: January 16, 2013, 09:23:09 AM »
Do you care about IQ?
70-200 II is not able to replace 85/135/200Ls in many situations...

IQ?  The 70-200 II is equal to or better than most of the primes in it's focal range in terms of IQ - basically, the differences are so minor as to be marginal in rigorous testing (charts/Imatest) and practically irrelevant in real-world shots.  The reason for the fast primes used to be IQ, shallower DoF, more light, and smaller/lighter (for a single lens, not the set).  At this point, for all practical purposes, it's down to shallower DoF, more light (debatable with a newer FF body and the excellent high-ISO performance) and smaller/lighter. 

6298
Lenses / Re: Question about variable aperture
« on: January 16, 2013, 09:14:58 AM »
A variable aperture zoom lens costs less fixed aperture zoom lens because it means the glass elements can be smaller.  Minimally, a lens elements must be sized to fill the iris diaphragm with light.  The diameter of the iris diaphragm is (focal length / f-number), e.g. a 200mm f/2.8 lens has an iris diaphragm of 200 ÷ 2.8 = 71.4mm...and thus, a 70-200mm f/2.8 zoom must also have an iris diaphragm diameter of 71.4mm at the long end, although a smaller diameter is needed at the 70mm end of the zoom.

An easy example to see this is the 100-400mm f/4.5-5.6L IS zoom - at the long end, the diameter of the iris diaphragm (and thus, the glass elements needed to fill it with light) is 71.4mm (same as 200/2.8 - twice the focal length, 2-stop narrower aperture).  If that lens were to be a 100-400mm f/4.5 lens, the diameter would need to be 88.9mm to support 400mm f/4.5.  That's closer to a 400/4 or 200/2 in element sizes than the current lens, so figure probably ~$5K for such a lens.  Not exactly a consumer-friendly price like the current 100-400...

6299
Software & Accessories / Re: Tripod, legs and ballhead grease - cleaning
« on: January 15, 2013, 08:49:59 PM »
I'd just give RRS a call...

6300
Canon General / Re: DxOMark vs. Reality
« on: January 15, 2013, 04:42:33 PM »
I suspect Neuro will tell me that I wasted 1 or 2 possible stops worth of DR on some of the shots by some of the method I used.

Highly unlikely.  Thanks for working toward sharing real-world examples, though (I don't consider a scenario intentionally chosen and designed to make a point to be 'real-world'). 

I've taken several thousand shots with a 5DII in the ISO 100-400 range, and guess how many I've rejected due to 'horrible low ISO FPN'?  Zero.

I should add, by way of maintaining objectivity and putting things in perspective: I've taken several thousand shots with a 5DII in the ISO 100-400 range, and guess how many I've rejected due to misfocusing by the less than stellar AF system of the 5DII?  Hundreds at least, likely thousands. 

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