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Tips & Tricks
Thread:
How to take a perfect Nadir - A Tutorial
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Re: How to take a perfect Nadir - A Tutorial
Posted: 20 Aug 2008 at 6:38 GMT
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This technique seems to work best on flat surfaces, and this begs the question - why not use a software solution?
PTGui Pro has viewpoint correction, which works excellently for this kind of nadir, with the added benefit of not only being much faster to create the nadir image, but also getting the camera out of the way if it is throwing a shadow on the nadir.
In many cases, smartblend kan avoid the bits of the 'slanted' nadir (the bits that stick out of the surface) that would otherwise be warped wrong, keeping the amount of post-processing work to a minimum.
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Forum:
Q & A
Thread:
Settings for Really Right Stuff Pano Head
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Re: Settings for Really Right Stuff Pano Head
Posted: 13 Jul 2008 at 19:15 GMT
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Oyvind Tryti said: Why do you need anything more stable than the NN5? The only reason I can think of, is to make panoramas using templates, which as far as I can see from the RRS site is impossible.
Hm... That didn't come across quite right.  I am of course in no way implying that the NN5 cannot be used for template stiching. But the RRS lacking rotator detents certainly prohibits it.
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Forum:
Q & A
Thread:
Settings for Really Right Stuff Pano Head
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Re: Settings for Really Right Stuff Pano Head
Posted: 13 Jul 2008 at 17:03 GMT
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Why do you need anything more stable than the NN5? The only reason I can think of, is to make panoramas using templates, which as far as I can see from the RRS site is impossible. The rotator does not seem to have any detents, which will make it impossible to get repeatable positioning which is mandatory for template stitching.
The RRStuff is expensive, and not very suitable for panoramas. There are plenty of other better alternatives.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 9 Apr 2008 at 19:52 GMT
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So, you didn't trust the distance scale, you tested. Good for you - I have been too trusting, and as a consequence having had to use it at 1 to 2 stops smaller than I could have if I had done the tests.
As I said - I really hope this is not a systematic fault of the Sigma, that only the ones with a bad copy (focus wise of course, sharpness seems to be good) are the ones responding to this thread.
On the other hand, the fact that several people have confirmed that the lens sets the focus correctly according to the distance markings, but that actual correct focus is at < 1 m might indicate a problem with the software in the lens. As such, there might well be a difference between the Nikon and Canon versions of the lens.
I will see if I can convince the store where I bought mine to let me test another one - they have more than 5 in stock at the moment. This can be done in a few minutes in the store.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 9 Apr 2008 at 18:35 GMT
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Hans, sorry about that. I was worried the discussion was heating up - I try to avoid that.
I saw that article before I bought my Sigma, and it was a contributing factor for me getting the Sigma instead of something else. By the way - the image is displayed correctly now.
I have been playing around a little with the depth of field calculator. I am making some assumptions here.
The maximum size panorama I can make with the Sigma 8/3.5 on a 40D is approximately 8000x4000 pixels. To keep maximum quality, the CoC can only be as large as a 2x2 pixel square, covering 1 red, 1 blue and 2 green pixels. Anything smaller will just get smeared by the anti-aliasing filter. That gives a CoC of 0.011 mm (22.2 mm / (3888/2)).
According to the calculator, the hyperfocal distance is
4.8 ft at f/4
3.4 ft at f/5.6
2.41 ft at f/8
1.56 ft at f/11
A smaller aperture than this will only lead to diffraction softening the image more than what is gained in depth of field. Even f/11 is iffy.
The markings on the lens seem to indicate that a CoC of 0.02 mm has been used for the calculations.
John, it seems that your lens behaves exactly like mine does - if anything, you have to set yours slightly closer than mine.
You say that this is where you tape it up in manual focus mode - is this because you know that this is the position for best focus at infinity, or are you setting it at the hyperfocal distance, and unintentionally focusing correctly for infinity?
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 9 Apr 2008 at 13:32 GMT
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Hans Nyberg said: I guess you do not know where the infinity is.
Hans, your link to ephotozine is broken.
And yes, I do know how to set a lens to infinity. I have been using and focusing lenses manually for 40 years, and this Sigma is the first lens I have encountered to be far off at room temperature. And yes, I am also aware of focus changing with temperature - that is why lenses are able to focus past infinity.
The Sigma is the only autofocusing lens I have (of the ones I have tested so far) that consistently sets the focus distance more or less correctly (at infinity, the vertical white line is placed a fraction to this side of infinity), whereas manual refocusing placed it at slightly less than 1m.
I am planning to make a page similar to yours available on my own site, but I will include pictures of the actual setting of the distance scale along with the images, in order to show how large the discrepancy can be.
The 500/4 was very impressive - auto focus was dead on, any adjustment I made would make the image less sharp.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 9 Apr 2008 at 13:13 GMT
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mhc1 said: But I´ve seen so many panos that are just made by setting the focus with AF - switching to manual and the shoot.
And they were remakable sharp !
That's exactly my point! Focus correctly on far objects, and let the close ones be a little unsharp - the final result is a very sharp looking panorama.
I cannot use this method with my lens - in any case, the focus ring turns so easily that I tape it down to make sure that it is not moved accidentally while the camera is turned from one stop to the next.
Hopefully this is a rare problem that only affects a few of the Sigma lenses, but owners should test to make sure that their copy is good.
Matt Rogers said: If this is the case then why would you keep the lens ? If my 8mm was blurry at infinity I'd return it for a new one.
The thought has struck me. I will talk to the store, but I have had it for more than a year before discovering the fault. That might be a problem, even if we have two years guarantee here in Norway.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 9 Apr 2008 at 6:47 GMT
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John Houghton said: Hyperfocal focusing is as valid now as it was in the past.
Agreed - as long as one knows what one is doing. But just blindly following the field of depth markings on the lens, which normally are calculated for film use, will lead to a hyperfocal distance that is too close to the camera.
The new lenses for reduced frame digital cameras may have field of depth markings using a smaller CoC - do you know if this is the case, John?
In any case, I think panographers that focus at the hyperfocal distance owe it to them selves to try out focusing at infinity, and compare the result (see the link in my first post for the rationale behind this statement).
If this focus problem with my Sigma is generic, it may be that people focusing their Sigma at the hyperfocal distance engraved on the barrel are accidentally focusing closer to infinity, and for this reason are satisfied with the result.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Re: Focusing the Sigma 8/3.5
Posted: 8 Apr 2008 at 21:55 GMT
updated: 8 Apr 2008 at 22:17 GMT
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Mike (mhc1), I find the monitor to be plenty good enough for critical focusing at 10X magnification. It is just a case of moving focus back and forth, and you will quickly find the correct point for optimum sharpness. I tried this with several lenses up to 500/4, and it is always easy to see when optimum focus has been achieved.
See this article about using live view for critical focusing: www.naturephotographers.net/articles0408/dw0408-1...
Unless you are making panoramas with very close details, you might want to try making one where the lens is focused on whatever is farthest away. You will stop down to f4 or f5.6 in any case for best quality, and if the closest object is the ground the tripod is standing on, you might be surprised at the quality of the panorama.
Hyperfocal focusing is really an outdated idea that was useful for film, where the size of the Circle of Confusion was used to determine the depth of field, and thus also what the hyperfocal distance is. The size of the CoC was determined by the final magnification needed. Modern digital cameras require a smaller CoC, because the magnification is larger, and the corresponding calculated depth of field is smaller. So, by setting the lens to the hyperfocal distance calculated for film, objects at infinity will actually be outside the depth of field. And in a panorama (except 'claustro-panos') you want distant objects to be as sharp as possible.
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Forum:
Tips & Tricks
Thread:
Focusing the Sigma 8/3.5
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Focusing the Sigma 8/3.5
Posted: 6 Apr 2008 at 23:05 GMT
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I have used the Sigma 8/3.5 on an EOS 400D for a year or so, and been satisfied with it.
My brother in law recently came from Phoenix, Arizona to Oslo to attend to our silver wedding. Since his P&S really seemed to be a POS, he was asking for advice on what to replace it with. The only logical thing for me to do, was to give him the 400D.
This, of course, gave me a good reason to get a 40D.
The 40D has live view, and I decided to have a look at the focusing of the Sigma 8/3.5. I autofocused it on something far away (the barrel stopped almost at the infinity mark), switched the lens to manual focus and checked the live view at 10x magnification. It was somewhat sharp, but not as good as I had expected. Then I adjusted the focusing until it was as sharp as possible. I looked at the distance marking, and was flabbergasted. It was set at just this side of 1 m! The test was repeated several times - autofocus would set the lens at infinity, manual refocusing would set it at just under 1 m.
I tested several Canon lenses too, none of them had this problem. It is possible to get more exact focus by using live view, but none of them were consistently far off like the Sigma was.
I photograph panoramas with my lens set for infinity (it is actually taped down). I want everything at a far distance to be in focus - this way anything larger than 2 mm will be recognizable as long as the lens can resolve it. See luminous-landscape.com/tutorials/digital%20focusi... for an explanation.
So, for the last year I have been using my Sigma focused PAST infinity! ARGH! No wonder my tests showed that I needed to stop down to at least f5.6, preferrably f8!
New tests show that best image quality is obtained at F4-5.6.
Owners of Sigma 8/3.5 might want to do this test on their own copy - if you have a camera with live view, it is a matter of minutes checking it. If not, a series of test images, where focus is changed a little for each image will tell you if this is a problem.
I trusted the distance scale, and did not test for focusing accuracy. The field of depth is so large at 8 mm, that it is not possible to see in the viewfinder that it not exactly right.
The fact that my copy of the lens does not autofocus correctly, and that the distance scale is wrong is of little significance to me, as long as I know what setting I should tape the distance scale at to obtain infinity focus..
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Forum:
Q & A
Thread:
Sigma 8mm sweet spot?
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Q & A
Thread:
CP5000 or wait more fore D200?
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Re: CP5000 or wait more fore D200?
Posted: 10 Jun 2007 at 19:55 GMT
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If you can buy either a Canon 400D or a Nikon D80, perhaps you should consider the D80 with a Nikon 10.5 mm fisheye. This lens is reputed to be slightly sharper than the Sigma 8/3.5 (you would probably have to use very good technique to see any difference). It is also slightly cheaper.
Here are some panoramas taken with 400D + Sigma 8/3.5: mejiatryti.com/Panoramas/May17.html
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Forum:
Q & A
Thread:
NN3 detents with sigma 8 3.5
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Re: NN3 detents with sigma 8 3.5
Posted: 10 Jun 2007 at 16:25 GMT
updated: 10 Jun 2007 at 16:28 GMT
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Ah, yes.
This is an early pano, taken with a Canon 1DMkII and a EF 17-40/4.0 at 17mm. This setup required 3 rows of 8 pictures for a total of 24 shots, and no nadir shot - the camera is too heavy to hold reliably. This is the reason I aquired first the Sigma 8/3.5, and later on the Canon 400D.
The EF 17-40/4.0 seems to have more flare/reflections than the Sigma 8/3.5, which is exacerbated by having to take 4 times as many pictures.
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Thread:
NN3 detents with sigma 8 3.5
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Re: NN3 detents with sigma 8 3.5
Posted: 10 Jun 2007 at 9:48 GMT
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I use a Manfrotto 300N rotator. It has 4 and 6 stops around, but not 5.
I tried using 4 around, but the difficulty in finding enough control points in the meagre overlap (I use Sigma 8/3.5 on Canon 400D) convinced me to always use 6 around. Taking the 2 extra pictures takes only a few seconds extra, but saves lots of time at the computer. There will be lots of area to create control points in (PTGui will normally find enough automatically), and also to adjust for quite large objects that have moved across boudaries between pictures.
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