October 30, 2014, 01:53:56 PM

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Messages - Sporgon

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527
Canon EF Zoom Lenses / Re: Canon EF 70-300 f/4-5.6L IS USM
« on: April 23, 2014, 04:14:55 AM »
Taken long after the sun had gone down, the mist rising from the river and meadows was filling the Stour Valley. The river can just be seen in the left of the picture, and the steeple of Dedham church is just right of centre.
Shot with the 6D and 70-300L @125 mil, ISO 1600, f5.6, 1/50th. A six frame hand held panoramic.

Lovely color palettes.  I find the color rendering out of the 70-300L to be excellent!

+1  I love panoramic shots and this is a brilliant piece of craftsmanship.

Thanks Peter & Dustin. I really like this one and it was good to capture such a serene, quiet part of the day.

528
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.

Are the corner pips really 100% crops? If so, the dof is indeed to wide to test the outer pt. performance. I don't doubt the outer af points focus *somewhere*, but they either tend to hunt (mostly on my 17-40L for some reason or another) or miss critical focus (indeed as speculated 70-300L @200-300mm, focus on the eyes).

What I was trying to show was that the AF accuracy at f1.6 was way more than f5.6. To this end the 2m dof was 'very narrow' compared with the 12m dof that f5.6 would have given.

The examples were in reply to the comments you made about this, and could be demonstrated by attaching the very small, but fast loading files.

The page has had around 1000 views overnight ( UK time) so hopefully some people have found it interesting, despite the ridicule of Mr Skirball.

The smallest dof that I can achieve with my gear is 6mm. This is with the 50mm at minimum focusing distance at f1.4. Please note: the 50mm f1.4 at minimum focus distance and f1.4 and off centre is crap.  I took three consecutive frames using the 2 o'clock outer point using the bottom of the eye as a target in low light; EV 3 to be precise. Each time, as before, I turned away focus manually so the camera had to re focus each time.

You will see that in each consecutive frame the camera has produced focus within the 6mm depth of field. There is perhaps a 1 or 2 mm variation, but the end result is the same: it's in focus. ( In fact at this distance this lens/body combo is back focusing a touch).

Now I would argue that for the vast majority of 6D owners ( and 5DII for that matter) this performance is absolutely acceptable.

The last frame is me attempting to manually focus using live view, but as you can see I have not succeeded; the manual focus on the 50 '1.4 just isn't good enough. I also tried live view contrast focusing but the focus zone is too big. 

I am not saying the 6D/5D AF is anything like the 1 series and 5DIII, but I am saying that people who state the outer points are 'useless', 'pointless' etc are talking out of their collective behinds.

The crops are 100% of full resolution. As I said, don't expect it to be razor with that lens at that aperture at that part of the frame.

There is one other thing to consider though: dust. I find that the single orientation points are highly susceptible to contamination by dust / pollen etc, and if you are struggling with your outer points on these cameras try using a rocket blower or even blower brush to get the dust off your AF module.




529
Consider that we are imaging three-dimensional space, and compare the XY dimension (FoV) to the Z dimension (DoF).  When magnification is low, the DoF is relatively large compared to the FoV.  For example, with a 50mm lens and 8 m distance, Z/X is ~0.4.  At higher mag, e.g., a close up of the dog with the 50mm lens at <2 m, Z/X is <0.1. 

Basically, misfocus is less obvious with a lower magnification.

Interesting, this explains why with longer lenses AF accuracy can be problematic even though there is a relatively large dof.

All I have tried to show is that the outer points on the 6D give infinitely more accuracy than an f5.6 dof - because there has been confusion in this thread about the meaning of an 'f5.6 precision' AF point, and that the outer points are perfectly useable in many circumstances whether near or far.

530
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.

+1

@ Sporgon, your 'very narrow DoF' looks to be over 2 m deep, distant subjects aren't as taxing for an AF system.

Even as a 6D owner I can laugh at the (unintended) sarcasm of posting pictures of “very narrow DoF” on the order of 2 meters.  See, the 6D can do f/1.6 as well!

If you look at the pictures of the bear at the top of the page you'll see a dof of 10mm with an outer point and it's accurate every time. ( The bear's nose is about 40mm long ). Some of the points being raised in this thread are based upon the accuracy of the 6D's outer point during movement and low light. Just how much movement and low light is anyone going to shoot with a depth of field of a few mm ?

Shooting at some distance with wide apertures requires AF accuarcy, despite the fact that real dof is much greater. Try shooting a moving target with the 135L at f2 at a distance of around fifteen metres with cameras that are not in the league of the 1D and see how you get on with a dof of 1.5m.

531
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.

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.

These pictures are intended to show that even at f1.6-8 on a 50mm focal length the focusing is accurate enough to drop the depth of field over the correct point of focus.

Where the two dogs are moving I was about two metres away, so dof would be about 18 cm. Where the individual ones are further away I would say eight metres, so a dof of 2.5m. However remember that at f5.6 you would have a dof of 12 metres with the 50mm lens, so 2.5 is 'narrow' in comparison with 12. 


532
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.

533
This whole subject of the 6D outer points has piqued my interest now. This afternoon I tried shooting moving and static subjects in both 'one shot' and 'servo' using just various of the outer points. Light was reasonable, EV 7 to  8, so not dark but not really bright either.

I put together a few shots, and you can see that the camera hits focus using a 50mm 1.4 at f1.6 - 1.8 very accurately with the outer points. I don't know what the engineering and physics are of the 'f5.6 sensitive points', but I can show you that these points nail focus on an appropriate target. "Appropriate' being the key word because you do have to be aware of the orientation you are using.

I would say one shot = 10/10 in reasonable light and appropriate target.  Servo on static subject = about 9/10. Servo on subject moving across your view = about 7/10. Remember this is f1.6 on a 50 mil. Servo on subject coming towards you fast = forget it.   

My point here is to show: A, that the outer points are quite useable in a number of situations, and:B, they are accurate to f1.6 on a 50mm focal length.

534
Lenses / Re: Will Sigma 50/1.4 Art push Canon to release a 50/1.2L II?
« on: April 21, 2014, 09:00:08 AM »
I don't think it will have much influence on the 50L as that lens is specifically bokeh before sharpness. The replacement for the 50 1.4 - well that's a different thing altogether. I wonder if the development of the 50 Art is what has delayed the Canon 50 IS ? Canon must have been aware of what Sigma were up to. I don't think Canon will reply with a mainstream retrofocal 50 design, but their own new 50 is going to have to compete. I think Canon will 'cheat' as they did with the 35 IS and produce a slightly slower traditional 50 design that has IS and is also really sharp at whatever aperture it is. I'm guessing f2, possibly f1.8/7, but almost certainly not 1.4 IMO.

535
If you go into the 6D's custom settings (Magic Lantern not required), you can set it up so you don't have to press the AF-point selection activation button (or whatever it's called - I assume you mean the button near the top right corner of the camera when you have you eye to the viewfinder) to select an AF point.  You can set it so you simply press the 8 way switch/dial to move the AF-point around.  It's still a very sad second best to having a joystick (like on a 7D/5D series/etc), but it's an awful lot better than having to press the AF-point selection button first every time you want to move an AF point.

Aaargh ! Why was this hidden in the 'Custom Button' function and not 'Custom AF' !?

Thanks jd7, that's a big improvement. I might have time to start complaining about the outer points now  ;)

As someone said' "CR is the manual" !

536
This really improves af w/ fast lenses? I don't have lenses faster than f2.8, but reading the specs the outer points only have f5.6 precision and are so near the f2.8 center point that my guess was that focus and recompose still is better than using the outer points? This is the reason I wouldn't buy a fast prime for the 6d with the intent to af, but I'm happy to stand corrected.

Yes indeed. I think f5.6 precision is misleading - it's requiring f5.6 to function. It will then not be as accurate ( in theory) as the f2.8 'precision' sensor.

Here are four consecutive shots taken with the 85 f1.8 at 1.8, three of which using some of the outer points. The contrast and lighting is good but it has got it bang on each time. As a comparison the last frame is with live view. These are 50% enlargement of a medium jpeg.

When using the single orientation outer points you must consider the detail orientation of the target. If this is done then I find the outer points very good in suitable conditions.

Don't let the outer points of the 6D stop you from getting a faster lens !

Just an addition: the distance here was 1 metre, so at f1.8 the dof was 10mm. At f5.6 the dof would have been 40mm, and f2.8 would have given 20mm. So you can see that this is concrete proof that the '5.6 precision' points give much greater precision than f5.6.

537
Which would be the point with the 6d: Is it better at anything, or is it really just a cheap version of the 5d3? It does have gps and wifi, that's obvious.

Yes it has gps and wifi. Personally these are of limited use to me but can be added to the 5DIII one way or another anyway.

But it does have other characteristics which set it apart from the 5D III. It is smaller and lighter, has interchangeable screens, and cost a lot less. We chose one for Building Panoramics and not only because it is cheaper.

Missing out the outer points altogether ? In the vast majority of static situations they work perfectly well when required for ultra shallow and close distance shots; ie. when 'focus and recompose' would give back focus.

The AF argument isn't really vs the 1D/5DIII system, it's against the cheaper cameras such as the 650D which have 'better' AF. I briefly had the 650D and didn't find it to be much difference.

As for the -3EV centre point, I have found that the 5DII will focus with the centre point in moonlight and I don't know what that's supposed to be rated at.

Funny isn't it that the 5DII was undoubtably 'crippled' by simple AF to keep it out of 1Ds III territory, yet the vast majority ( for a marketing point of view) still chose to use it over the 1DsIII, eventually resulting in the dropping of that line, and upgrading the 5D line to full professional status.

There are much more annoying things about the AF of the 6D than the points themselves; having to use the 'rebel' interface of first having to press an activation button before you can press the point moving button is much more of an issue.

538
Landscape / Re: Post Your Best Landscapes
« on: April 21, 2014, 02:09:28 AM »
First post on the forums, taken in Wellington, NZ

Really like this, I think you've got the HDR balance spot on.

539
Photography Technique / Re: Am I the only one this has happened to?
« on: April 20, 2014, 05:39:34 PM »
Sign of the times I'm afraid. The guy's out of order. He could have requested you don't take any pictures of his kids, but doesn't sound as if he had any there yet be was hanging around the park with the kids himself.

If you're going to take pictures in these kind of situations nowadays I suggested you get a CRB certificate or what ever is the equivalent in your country. I have one for the Building Panoramics work I do around the schools and colleges.

In that sort of situation you can have a copy and produce it for anyone who challenges you. Whether it would pacify the jerk you came across is unknown.

Unfortunately expect more of this kind of thing.

The real perverts are the ones who see everyone else as a potential pedophile all the time.

540
Canon EF Prime Lenses / Re: Canon EF 50mm f/1.4 USM
« on: April 20, 2014, 03:02:08 PM »
Playing about with my daughter's 1100D. I'm surprised by how much latitude there is in the RAW data. I can pull it around much more than I thought would be possible.

This is just one exposure, no flash, shot on the 50/1.4 @ about f2.8. ISO 200
Bokeh looks good. 2008 is when I first got introduced to dslr. 40d and 50mm f1.4

Thanks Dylan, I find the bokeh of the 1.4 lens can be quite good if the scene is right.

Here's one that I just couldn't resist; shot at f1.6

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