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Archive 2019 · M43 - Handheld panos- focal length / exposure?

  
 
WanderNWonder
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p.1 #1 · p.1 #1 · M43 - Handheld panos- focal length / exposure?


Hello again to everyone,

I've received a ton of awesome advice about M43 equipment in my other thread.
I have a related but different request this time. Apologies for the lengthy post..

I often take Multi-row handheld panoramas (sometimes in cathedrals/churches) - so far I've done this using a DSLR (ff or APSC), by taking RAW files which I stitch in LR or PS. Typically I take up to 3 rows (center, top, bottom). Sometimes I also take single row front-to-back panos along the vertical axis.

For indoor panos, the toughest settings were with a handheld APSC - I used f/11, 1/20 s, ISO 2000, 50mm - and due to the crop FoV it required more images than an FF. Things were a bit easier when I use an FF (I have to hold my breath fewer times) to take fewer images, and can push the ISO higher.

I'm curious to know if there's any focal length / lens in the M43 space that works best for this workflow?

The two aspects I'm unsure about are

1. which focal length would have the least keystone / perspective distortion on the G9/EM1.2, so that the RAW images can be stitched better? Some of my previous sets have caused LR / PS to trip up due to distortion when I used short focal lengths.

A longer focal length requires more frames, and a shorter focal length would have more distortion when pointing up / down to take the frames for the top / bottom rows.

With M43 only the central portion of the FF FoV is used, and the camera is supposed to apply distortion correction, so I'm guessing there should be a focal length shorter than 50mm, which would have negligible center distortion.

2. For indoor panos, what should be the preferred exposure for such images on an M43 body such the G9 or the EM1.2?

Based on the worst-case example above and given the min 5.5 stops of IBIS on G9 & EM1.2, theoretically, I should be able to use: f/5.6, 1/125, ISO 800 for such cases.

I'm not sure if that's the right way to think about it? Any tips / advice would be great!

Thanks in advance,
Arun



Dec 14, 2019 at 08:04 AM
bobbytan
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p.1 #2 · p.1 #2 · M43 - Handheld panos- focal length / exposure?


I was given to understand that a 50mm lens (in FF terms) is best for stitching panos as there is less lens distortion. So I would think that the new PL 25/1.4 would be a good lens for that purpose ... or a zoom lens at that focal length?


Dec 14, 2019 at 03:08 PM
AJSJones
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p.1 #3 · p.1 #3 · M43 - Handheld panos- focal length / exposure?


Exactly the same considerations apply to M43 as to APS-C, when you adjust the "crop factor" from 1.6 to 2.0. You cannot avoid the perspective distortion (on any format) that comes from not having the sensor plane vertical: converging/diverging verticals etc. The stitching software can be configured to different geometries - I always use cylindrical in the Photoshop options, but I rarely do multi row. The main reason to do multi-row is to be able to use a longer FL and avoid the intrinsic geometric distortion that arises from the short FL. (Compare objects at the edge of a UWA lens image with the same objects in the centre of the FoV - that is not lens distortion, it is geometry) Also, the wider angle lens used, the more likely you are to have parallax/stitching problems, when there are significant objects at different distances, if the camera is not maintained on the lens nodal point for both axes. That problem gets worse as you use shorter focal lengths. The M43 system allows the software to remove the (usually quite small) geometric imperfections in the lens, but it's better, (but more $) to get a higher quality lens at any FL. I suggest following the advice above - use as long a FL as you can to get the stitched FoV using the number of rows/columns you need to get to the total MP in the final image. (I presume you are doing panos to increase the MP count.) A good 25mm M43 lens should do well for many/most situations, depending on your specific goals.


Dec 18, 2019 at 11:07 AM
jeffbuzz
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p.1 #4 · p.1 #4 · M43 - Handheld panos- focal length / exposure?


I absolutely agree with bobbytan and AJSJones. The less optical distortion in the lens the better. Typically, macro lenses offer the best "flat field" performance with the least distortion. I can vouch for the Olympus 60mm macro being incredibly good. According to dxomark the Pana-Leica 45mm macro actually shows zero distortion which is astonishing. I have not tried that lens yet but given its slightly wider angle of view it might work better for your purposes.


Dec 24, 2019 at 01:29 AM
WanderNWonder
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p.1 #5 · p.1 #5 · M43 - Handheld panos- focal length / exposure?


bobbytan wrote:
I was given to understand that a 50mm lens (in FF terms) is best for stitching panos as there is less lens distortion. So I would think that the new PL 25/1.4 would be a good lens for that purpose ... or a zoom lens at that focal length?


---------------------------------------------

AJSJones wrote:
Exactly the same considerations apply to M43 as to APS-C, when you adjust the "crop factor" from 1.6 to 2.0. You cannot avoid the perspective distortion (on any format) that comes from not having the sensor plane vertical: converging/diverging verticals etc. The stitching software can be configured to different geometries - I always use cylindrical in the Photoshop options, but I rarely do multi row. The main reason to do multi-row is to be able to use a longer FL and avoid the intrinsic geometric distortion that arises from the short FL. (Compare objects at the edge of a UWA
...Show more


Thank you, @bobbytan and @AJSJones,

There are 4 occasions when I use multi-row panoramas: indoor shots, exterior shots, some rare situations when I prefer to keep my composition squarish when shooting landscapes, and some cases when I want more of the foreground.

Below are some examples:





I can split my question into two parts:
1) Seeking guidance about focussing distance and aperture:
I'm struggling with what focussing distance and aperture I should be using for good front-to-back sharpness when shooting indoor panos. The indoor panos are tricky because they are side-to-side and top-to-bottom, and the distance varies a lot, especially when there are pillars in the scene. If I use the wrong focusing distance at f4 or f2.8, those shots won't be stitch-friendly.

There's been some debate about hyperfocal vs 2xclosest-object-in-frame for getting reasonable front to back focus. I'm not sure which of these is the preferred method for wide open apertures on MFT.

2) Multi-row with 25mm on MFT:
Is this even a good idea? Is the distortion caused by the "real" focal length (not effective fl) too great at 25mm for multi-row panos ?
If so, I may have to stick to using the Nifty-50 on FF for indoor multi row panos.



Dec 24, 2019 at 02:46 AM
AJSJones
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p.1 #6 · p.1 #6 · M43 - Handheld panos- focal length / exposure?


The issue of focusing is no different for panos than it is for single shots - except for making sure that the aperture is set to cover the near and far points if they are in different frames. I used to use a 4x5 view camera and used DoF tabes to set an initial aperture . Composition was done wide open but focus was checked with a loupe (in a range of positions) once the lens was stopped down to the taking aperture. Today this would be done by using Live View zoom and DoF preview ( a lot easier). I often use that for single shots as well as panos, especially with tilt-shift lenses. Your mention of "rules" for "how to do it" may be useful for starting point but I would advise NOT to rely on either of them. You seem (rightly) concerned with sharpness, so avoiding narrow apertures is a good goal (diffraction can be detected from f/8 or so if you make large prints) so "stopping down to f/16 or f/22 is a bad "routine". How large do you plan to print? However, with scenes having a large range of distances something has to give A full zoom in on Live View while holding the DoF preview (or take the shot and review with magnifier - probably easier if no tripod) and check the near an far points. If focus is not acceptable, stop down more, rinse and repeat. You might wish to check out the on-line depth of field calculators to get an idea of what's going on. If you print large, then you will have to set the CoC close to the size of the pixels. If you only make 8x10 sized prints, then you can use the CoC the calculator typically uses for your format.

As for the 25mm on M43 and 50mm on FF, the distortion issue is no different (assuming a lens with no significant optical distortion). The choice of 50 on FF is because it appears "normal" to the eye. (the FL is close to the diagonal of a 35mm frame). Same is true for 25mm FL on M43 frame. The M43 gives you some advantage in increased DoF for a given composition but print size also has a big role to play (as does viewing distance). For your church/cathedral indoor shots with near pillars and far windows, you will likely have to stop down a lot (increasing the possibility of diffraction softening the whole image a bit). Also, for max sharpness, most lenses need to be stopped down somewhat - check out Roger's article comparing several M43 25mm lenses here https://www.lensrentals.com/blog/2018/01/finally-some-m43-mtf-testing-25mm-prime-lens-comparison/ Sharpness increases as you stop down - at the edges of the frame the Pana/Leica 25 f/1.4 is sharpest at f/5.6, while the Olympus f/1.8 is sharpest at f/2.2 in the centre, while the edge performance is relatively constant out to f/5.6 (everything goes down once you reach f/8). (From opticallimits.com). If you are closer to a perfectionist and make large prints where you want to see maximum detail, you night consider focus stacking - not great for subjects with any motion but your subjects seem to be rather still And, of course, you will do better the closer you can get to keeping the lens in the same place as you change the angle of the camera - only really important if there is a lot of action very close to the camera



Dec 24, 2019 at 11:44 AM
WanderNWonder
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p.1 #7 · p.1 #7 · M43 - Handheld panos- focal length / exposure?


AJSJones wrote:
The issue of focusing is no different for panos than it is for single shots - except for making sure that the aperture is set to cover the near and far points if they are in different frames. I used to use a 4x5 view camera and used DoF tabes to set an initial aperture . Composition was done wide open but focus was checked with a loupe (in a range of positions) once the lens was stopped down to the taking aperture. Today this would be done by using Live View zoom and DoF preview ( a lot easier).
...Show more
Interesting! Thanks for the tip

AJSJones wrote:
Your mention of "rules" for "how to do it" may be useful for starting point but I would advise NOT to rely on either of them. You seem (rightly) concerned with sharpness, so avoiding narrow apertures is a good goal (diffraction can be detected from f/8 or so if you make large prints) so "stopping down to f/16 or f/22 is a bad "routine". How large do you plan to print? However, with scenes having a large range of distances something has to give A full zoom in on Live View while holding the DoF preview (or take the
...Show more

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?



Dec 25, 2019 at 01:02 AM
AJSJones
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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...



Dec 25, 2019 at 11:54 AM
WanderNWonder
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p.1 #9 · p.1 #9 · M43 - Handheld panos- focal length / exposure?


Thanks, @AJSJonea for the fantastic detailed explanation!
Much appreciated, thank you for taking the time to respond with extensive details.

I learnt a lot, to say the least In terms of viewing, my purpose is to print 12-18” on the shorter edge of the pano. But a large fraction of my panoramas may not get printed due to the limitation of space to display them at home

So the viewing experience will mostly be online, with the longest edge being at 3000px.

The technique you mentioned, for finding the right focusing distance is interesting. I will give it a try at home to get some practice.

AJSJones wrote:
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
...Show more



Dec 25, 2019 at 08:48 PM
AJSJones
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p.1 #10 · p.1 #10 · M43 - Handheld panos- focal length / exposure?


I have the sane problem of not enough wall space
With your dimensions, I don't think the issue will be problematic. Stitching 4 frames of 20 MP (OK 6 with overlap resulting in 80MP final and using 300 ppi for printing (9,000 x 9,000 pixels = 81 MP), you will have enough for ~30" x 30". I often print at 240 ppi and still have detail distinct with my nose close to the print! This means you won't be geometrically enlarging any blur as much, whether it is from diffraction, too slow shutterspeed or beginning to get OOF (the edge of the DoF. Those all get worse the bigger you print. So you can stop down a bit more, have a little handshake or more DoF (but probably not all three!) It's still a good idea to go through the learning exercises above (in case you ever do want to make a big print if a project succeeds beyond your vision). With a little experimentation, you will get the hang of it and won't need to check many shots on site, to confirm near and far are acceptable (I always check one shot - or use the DoF button - at the taking conditions to check before doing any multishot, but after a while your initial guess will be good enough. Have fun - your shots above are already encouraging -



Dec 25, 2019 at 09:43 PM
WanderNWonder
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p.1 #11 · p.1 #11 · M43 - Handheld panos- focal length / exposure?


AJSJones wrote:
I have the sane problem of not enough wall space
With your dimensions, I don't think the issue will be problematic. Stitching 4 frames of 20 MP (OK 6 with overlap resulting in 80MP final and using 300 ppi for printing (9,000 x 9,000 pixels = 81 MP), you will have enough for ~30" x 30". I often print at 240 ppi and still have detail distinct with my nose close to the print! This means you won't be geometrically enlarging any blur as much, whether it is from diffraction, too slow shutterspeed or beginning to get OOF (the edge
...Show more

Thank you for the encouragement and advice, @AJSJones
I played around with the 25mm prime, and was able to get some semblance of hyperfocal, with the help of focus peaking. That got me an "almost sharp" interior pano, except for the corners.

I don't think I would have the desire to mix any kind of bracketing or stacking with panoramas though as I think I'm shooting a large number of frames. For the basilica interior, I used 62 images across 6 rows. For the Basilica exterior, I used 70 images in 4 rows. Maybe I need to stand further back.. A challenge I do face with the 25mm is detecting whether the focus is sharp at the far end, on the LCD. I'm hoping that with more practice it will eventually get easier.



Jan 01, 2020 at 01:08 PM
AJSJones
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p.1 #12 · p.1 #12 · M43 - Handheld panos- focal length / exposure?


Zooming in as far as possible and looking in the corners will tell you whether you have focused it correctly. My hat's off to you for taking 60 images for a single pano. Can you tell me what the pixel dimensions of the final pano were, right after stitching? I would only ever dream of attempting/needing so many shots if I knew I was going to print HUGE (Google GigaPixel!). In my opinion, you are wasting effort if your output is only ever as small as you noted above! How are you doing with the experiments I suggested - they are the best way to find what works for you and your equipment. For any new lens, one thing I do is use a tripod to take a series of shots of the same scene at different apertures and review sharpness across the whole image - to see how well it does. As you stop down, you will notice general improvement for most lenses, but especially at the edges. However, the more you stop down to gain DoF, the more you will lose sharpness due to diffraction - only you can tell where the best balance of DoF vs sharpnss is concerned - and then you should only critically evaluate it in the final print, if you never intend to print larger.


Jan 01, 2020 at 05:04 PM
Fjhleger
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p.1 #13 · p.1 #13 · M43 - Handheld panos- focal length / exposure?


60 is a lot, but i did some large panos about this size (48+) as i had the opportunity to use a not too bad tele lens on a large building, or montain pass face while being quite close. This compensated for the relatively low number of pixels of my camera while providing huge details. Of course, this end up being too large to print, but this is inexpensive to take and allows to crop…
Using the (now defunct) Kolor autopano to join the photos is easy, rapid and effortless.



Jan 02, 2020 at 03:40 AM
WanderNWonder
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p.1 #14 · p.1 #14 · M43 - Handheld panos- focal length / exposure?


AJSJones wrote:
My hat's off to you for taking 60 images for a single pano. Can you tell me what the pixel dimensions of the final pano were, right after stitching? I would only ever dream of attempting/needing so many shots if I knew I was going to print HUGE (Google GigaPixel!). In my opinion, you are wasting effort if your output is only ever as small as you noted above!


Very true, I realized I had overdone it after LR and PS both were unable to process the panorama Then I had to export 1000px downsized TIFFs and stitch them in PS, I believe that too were into the 30000px on the long side. I downsized that to 6000px before saving.
There were three reasons I ended up shooting so many: (a) I used 50mm on an APSC body and (b) I was not standing far back enough. (c) as a result of [a] and , I covered almost 160 degrees left to my right, and top to bottom. A big chunk of that got lopped off in the pano stitch at the edges. If I had used a shorter focal length or stood further back I think I would have gotten away with a narrower angle/field of view.

AJSJones wrote:
How are you doing with the experiments I suggested - they are the best way to find what works for you and your equipment. For any new lens, one thing I do is use a tripod to take a series of shots of the same scene at different apertures and review sharpness across the whole image - to see how well it does. As you stop down, you will notice general improvement for most lenses, but especially at the edges. However, the more you stop down to gain DoF, the more you will lose sharpness due to diffraction - only
...Show more
Thanks a bunch again for the advice, @AJSJones
I have been playing with trial m43 equipment, and will be finalizing a purchase hopefully soon. The learning and experimentation will commence in earnest after that. The 25mm f1.8 is going to be part of that kit for sure.



Jan 02, 2020 at 12:15 PM
WanderNWonder
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p.1 #15 · p.1 #15 · M43 - Handheld panos- focal length / exposure?


Fjhleger wrote:
60 is a lot, but i did some large panos about this size (48+) as i had the opportunity to use a not too bad tele lens on a large building, or montain pass face while being quite close. This compensated for the relatively low number of pixels of my camera while providing huge details. Of course, this end up being too large to print, but this is inexpensive to take and allows to crop…
Using the (now defunct) Kolor autopano to join the photos is easy, rapid and effortless.


I used to try these close up "get everything in frame" shots with UWA, and found that it wasn't to my taste. I didn't want to put money into a tilt-shift lens so I just took the cheaper way out by taking a hand held panos


Among the various softwares I tried, I found PS and LR doing the job the best for my handheld panos. I believe some folks are using PtGui, ICE and Hugin, but I haven't given those a serious try yet.

My hope is that some day, TV screen & monitor resolutions will be high enough to warrant these mega size stitched panos. And hopefully storage will continue to get cheaper, to store all these raw files



Jan 02, 2020 at 12:23 PM





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