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p.1 #8 · p.1 #8 · M43 - Handheld panos- focal length / exposure? | |
WanderNWonder wrote:
Thanks a ton, for the tips, and the links, @AJSJones@
Photopills suggests, that at 25mm with f/5.6, if I focus at any distance beyond 7m, I should get infinite DoF (I understand that this means "reasonably good"). However I'm unsure about how to set the precise focusing distance to get infinite DoF. Does one use a laser measurement tool to find a spot to focus on? Or is it just a guesstimate?
The number from Photopills assumes you are making a print ~8" x 10" and view it from about 12". They have an "advanced" DoF calculator that requires you to enter your values for those pieces of information - that's why I was asking you those questions If you do a 2 row 3 panel pano (6 frame area) and print it to 8 x 9 proportions (from a 4:3 capture for each frame), how big do you expect to print that and how close will you (or your friends/clients) approach it to view the details? You can play around with those numbers and see how misleading the "traditional method can be if you enlarge the capture more than the old film based "8x10 from a foot or so" method. Hint : for a 24x33 print viewed from a foot, your number won't work very well
Rather than try to do it by "calculation", I suggest using/borrowing a tripod for a few experiments where you can simulate a typical subject and zoom in on the LiveView - set the aperture at various settings. At each setting, use the Dof preview button and zoom in (all the way) on the far point (the name for the furthest plane you want to be in focus (the stained glass window in the distance or the horizon in a landscape) and rotate the focus ring from "in focus" until you can see it begin to get less sharp and go back a little till it's just in focus again. Then, with the DoF button still pressed see what is the closest point that is in focus (the near point). If the pillars or foreground flowers are not in focus, you will need to stop down more and repeat. This gives you real-world experience in which aperture yields one where you desired near and far points are in focus.
Possibly a simpler approach is to ask "What is the maximum DoF I can ever get?" and a reasonable answer to that is "The one you get by setting the CoC to the size of a pixel." (That is because you will not be able to detect the "out of focus" blur if it is smaller than a pixel.) Then you can use a calculator (one that lets you input CoC) and derive the DoF. Note that you may need to stop down so far (to achieve the DoF you want) that you incur some (a lot) of diffraction blur penalty - however, the DoF will be correct, but the WHOLE image will be blurred a bit(a lot). That's just physics Once you decide/reveal how large you want to print, we can talk real numbers.
In the meantime, you can eyeball 7 meters (~20 ft), set the AF on that point and take a series of shots at f/2, f//2.8, f/4 etc and then review them when you zoom in to max zoom (or 100% pixel level on a computer) and estimate the distances of the near and far planes to get a feel for what is happening. If you keep going to f/8, f/11, f/16 you will see the effect of diffraction softening - and may be disappointed in the laws of physics You will soon appreciate the balance between maximum DoF with sharp as possible and maximum DoF with "acceptable sharpness". In extreme conditions, perfectionists will "focus stack" each frame (and some even exposure bracket those!!!) Have fun over the holiday season.
Edit: just noticed the title and the question on exposure: I will survey the scene I want to capture and find the brightest area where I want to keep the highlights from blowing and set the exposure for all the frames (on manual) so that part of the scene is exposed how I want (exposed to the right if appropriate to maximize dynamic arrange). So the required shutterspeed/aperture/ISO combination is fixed, and the same for each frame. If the DoF requires one particular apreture then the ISO/SS will be set by how well I can handhold (using the IS if available) - this part may be the most critical for maximum sharpness.... Tripods are extremely helpful here - I've paid modest fees to use them in cathedrals and a small one hiking for landscapes is also worth its weight in gold, or carbon fibre, or ... The limitation of "hand-held" is a huge negative for sharp panos Once you have determined (from tripod work) what the optimal aperture/ISO is at the shutterspeed you plan for handheld you can compare the handheld with the tripod to see how well you do, sharpness-wise. Some people will fire off several electronic shutter frames for each pano frame to increase the likelihood of one being sharper than the rest...
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