July 29, 2014, 12:44:42 AM

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Messages - 3kramd5

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106
To further add, my 1Ds3 and 1Dx never miss at f/1.4 on the outter points.  Never.  Always exact.  No variability.  Nails it everytime and that's even without AFMA.

it is physical impossibility because the AF  measurement angle accuracy in Canons AF is  F-2,8  ( eg.3,4)


That's not correct.

The specified precision is within the depth of focus at the max aperture of the lens for a standard precision AF point, and within 0.33 depth of focus (0.5 for some models) at the max aperture of the lens for a high precision AF point. 

I discussed this issue with Chuck Westfall (Canon USA's technical mouthpiece), and this is part of his response:

"The fact that the AF points are functional with apertures as small as f/5.6, f/4 or f/2.8 respectively depending on the camera model and AF point under discussion does not imply that their measuring precision is limited to the depth of focus at those apertures. The AF detection system has the capability of calculating depth of focus based on the maximum aperture of the lens, whatever it happens to be."


I've been doing some reading and came across a pertinent point. Your post above relates specifically to high-precision AF points. The outer points are not high-precision, unless I misunderstand him here: "...one of the consequences of the TTL-SIR AF system is that except for the center point, AF precision is not proportional to the maximum aperture of the lens in use."

Of course, that's a 70D-centric dialog. Maybe some of the outer 1Dx/5D3 cross points are included.

107
Narrow depth of field is relative to the distance. If you are taking a picture of a football field and have the centre line in focus with a depth of field of two metres; that's narrow.


Finding the exact plane of focus is the real trick. The problem with those images is it's impossible to see where that plane is because it's surrounded by so much volume of sharp focus. To me, it doesn't illustrate what you intended it to even if the camera focused dead nuts where you wanted it to.


Focus here is on his right eyelashes, and the photo would have been a reject had I been wider than f/2.8.




I love your panoramics, btw. Never had a chance to talk with you before on this forum. Kudos.

108
I've made them fit the page but have included a magnification in each one where you can see that the very narrow dof has been achieved over the focus point.

Not to be argumentative, but that isn't a particularly narrow dof. How far away is the dog?

Narrow to me means if you hit eyelashes, the retina is OOF.

edit: I have no idea why my post is nested in yours. Weird.

109
and I suspect if being able to AF at -3EV gave a significant practical benefit in many circumstances, it would have found its way into the 1Dx and 5D3 (although I suppose it's just possible it wasn't ready in time for those cameras but it was ready in time for the 6D).

Maybe the sensor needs to be physically larger to be that sensitive and doesn't lend itself to a dual cross type configuration. But I think practicality probably has more to do with it. Someone spending money for a sports/bird AF unit likely won't be impressed by the capability to AF in a situations where long exposures and tripods are required - just manually focus using LV at that point.

For all that though, I suspect the 6D's AF is probably "good enough" for many people much of the time. 

No doubt. There are thousands of great images taken with 5D2 AF, or older, or manual focus cameras. The 1Dx / D4 AF capabilities are nice-to-haves, not need-to-haves. They no doubt improve hit rate, but aren't strictly necessary.

110
Additionally, he adds in that the 1Dx and 5D3 would have never AF'd in a particular situation that the 6D did.  He also makes the accusation that we've never shot with the 6D so how can we comment?

1.  The 1Dx and 5D3 would have easily AF'd in that case, so that point right there is simply objectively WRONG.
2.  He hasn't shot with the 1Dx or 5D3, yet makes the above comment.  Talk about the pot calling the kettle black. 

Is he for real?  There's NO WAY any sane person could both make the arguments he's making and simultaneously believe in those arguments.

The AF system of the 1Dx is best = $6799
The AF system of the 5D3 is second best = $3399
The AF system of the 6D is the "least good" out of all 3 = $2000 ish

Hmm, surprising!

It's just silliness. The 6D is a nice, affordable 135 format DSLR. It has some nice features, but AF is hardly its selling point. -3LV autofocus, as has been pointed out, has some significant practicality issues.

Who the hell ever said the 6D's autofocus was a "selling point"?  Not me.  I'm calling b/s though, and that's now your color.

Wow. Relax, Carl. It's a turn of phrase. I intended it as synonymous with "strong point."

I don't even know what you mean by the bit about color... ?

111



Can someone please explain dumb me what does focus at "-3ev" actually mean? Thanking in advance.

Exposure values were initially used to merely compare exposure settings, and settings independent of film speed. EV0 was defined as 1sec at f/1. In this context, it is assumed to be at 100ISO (ISO100, aka light value). EV0 light would require f/1 at 100 for 1 second or equivalent to properly expose. EV-3 is three stops darker, or f/1 at 100 for 8 seconds, or f/0.7 at 200 for 2 seconds, etc. In other words, it's dark.

112
Animal Kingdom / Re: BIRD IN FLIGHT ONLY -- share your BIF photos here
« on: April 19, 2014, 06:00:08 PM »
Immature Rufous Hummingbird from Monday.



Superb.

Here's my only recent BIF (teehee):


113
Additionally, he adds in that the 1Dx and 5D3 would have never AF'd in a particular situation that the 6D did.  He also makes the accusation that we've never shot with the 6D so how can we comment?

1.  The 1Dx and 5D3 would have easily AF'd in that case, so that point right there is simply objectively WRONG.
2.  He hasn't shot with the 1Dx or 5D3, yet makes the above comment.  Talk about the pot calling the kettle black. 

Is he for real?  There's NO WAY any sane person could both make the arguments he's making and simultaneously believe in those arguments.

The AF system of the 1Dx is best = $6799
The AF system of the 5D3 is second best = $3399
The AF system of the 6D is the "least good" out of all 3 = $2000 ish

Hmm, surprising!

It's just silliness. The 6D is a nice, affordable 135 format DSLR. It has some nice features, but AF is hardly its selling point. -3LV autofocus, as has been pointed out, has some significant practicality issues.

114
ken rockwell says the 6d af is better than the 5diii which is too complicated. the 6d af doesn't get in the way, it just works baby!

After all, you can AF at LV-3 with the center point, then recompose on your tripod, and get a nice, steady image of an OOF subject. Can't possibly do that with a 5D.

115
the focus plane is the same in every picture at F 1,4

Bold statement implying that the only way to focus a prime f/1.4 lens is to move it (which is demonstrably false). Again, what is the explanation for how AF f/>2.8 images were achieved using canon bodies? Did the camera stop down to focus?

116
show proof that I am wrong,  the AF  measurement angle accuracy in Canons AF is  F-2,8
I know Im right
it will be interesting!!!!

So you're suggesting that the sensor pair is too narrow to see beams from lenses wider than f/2.8? If that's the case, how do you believe any number of images online shot using canon AF at apertures in the f/<2.8 range were focused? Does the camera actually stop down to focus (as opposed to the normal practice of focusing wide open)?

117
Its not really comparing apples with oranges because the Eg-S allows you to see in the viewfinder more accurate DOF - even when autofocusing - than the 5D3's stock screen which is not user replaceable.  5D3's fixed focus screen only shows about f/2.8 DOF while the Eg-S on the 6D will come close to the DOF of f/1.2.

So, the fact that the 6D allows the user to swap to Eg-S means that what you see in the viewfinder when both AF *and* MF will more accurately represent the end product.  If you do choose to MF to that end product, it is worlds easier on the 6D using Eg-S vs the 5D3's fixed screen.

Yes, the 5D3 will likely allow to set up your shots faster, but that does not make the 6D AF useless.

Indeed. The lack of replaceable focus screens is one of the annoyances of the 5D3 (cost being the primary annoyance). I can live with it, however. When I have the luxury of setting up my shot, I generally manually focus with live view.

I don't think anyone has said the 6D AF is useless. Thousands of photographers have used it for years with the 5D2 (no, they aren't identical, but for all intents and purposes one uses them the same way).

No, it's not useless. But it isn't even remotely like the 1Dx unit, or the almost 1Dx unit in the 5D3. Even in one-shot (which I use exclusively with my 5D2 and much of the time with my 5D3), having reasonably accurate points covering about 2/3 of the width of the frame allows for thin DOF AF with a much higher hit rate. And when you consider tracking, it's apples and paperclips.



I feel like the back button focusing isn't as reliable -or maybe I'm doing it wrong. Are you supposed to be holding the backbutton(what I've been doing) or just press it once? I'm shooting in AI Servo.

It's exactly as reliable. Whether you engage AF with the shutter release or the AF-ON button, what follows is identical.

If you're in Servo, you're doing it right: hold it down, including when you release the shutter.

118

The lateral points are vertical line sensors, meaning they detect horizontal lines

Ah yes, pardon the brain fart.

119
I thought you were discussing side AF points.  Those eyes look pretty centered in the FOV to me, unless this is heavily cropped...which I doubt.

Did you read the description? There is no crop. Her right eye is near the center of the frame, and because she is nearly parallel to the sensor plane it is in focus. But AF was on her left eye.

"1st photo SOOC, untouch: 5D III + 85L II, 1/160 @ f1.2, outer AF point, was focus on her left eye"

I get that kind of performance from my 5D3 outer cross-type points too (in one shot, I disable non-cross type AF), at least as best I can tell with shallow DOF from say 200mm/2.8.

5D2? Not so much. The 6D outer points are vertical line sensors like the 5D2, right? In landscape orientation it will just hunt on the outlying points if there is no vertical contrast. The 1Dx unit is sensitive in two directions widely across the frame. That's a significant improvement over the 5D2/6D.

I don't know of anyone who wanted a 5D3 at 6D prices.  Rather, I suspect there are plenty who would pay $4500 for a 5D3. 

Willingness to pay and a desire to pay are two different things. I certainly would have wanted a 5D3 at 6D prices. However, that's unrealistic.

As for there being plenty who would pay $4,500... I don't know. There may be some, but at that point, many may look elsewhere or decide to save a little bit more for the 1Dx.

120
EOS Bodies / Re: Canon 5D MarkIII & 1Dx - 1080p/60fps???
« on: April 14, 2014, 02:34:07 PM »
the 5diii was a very small improvement (leaving AF aside) over the 5dii.

Sorry, i find that exceedingly funny. Leaving aside the paramount major upgrade, it's a small improvement. That's like complaining that setting aside the hybrid engine, the hybrid version of a car is a minor upgrade over the gas one.

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