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Thread: Creating Pano

  1. #21
    Moderator ziploc's Avatar
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    Default Re: Create

    Welcome and have fun playing.

  2. #22
    Moderator ziploc's Avatar
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    Default Re: Create

    Quote Originally Posted by Fragnatic View Post
    wow, u've overlapped a lot. that's like 60% overlapping. no wonder u've got 27 frames.
    Haha ya, it is better be more KS and have more overlapping, then to find out later that there is a break in between that the frames cannot connect. There is no harm in overlapping more, and extra frames can always be removed later if not needed. The 20-30% overlapping is just a rule of thumb.

  3. #23
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    Default Re: Create

    Haha ya, it is better be more KS and have more overlapping, then to find out later that there is a break in between that the frames cannot connect. There is no harm in overlapping more, and extra frames can always be removed later if not needed. The 20-30% overlapping is just a rule of thumb.
    oic. i thought overlap more will be more beautiful. hehe...
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  4. #24

    Default Re: Create

    Visit panoguide.com for panoramic photography tips.
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  5. #25
    Moderator ziploc's Avatar
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    Default Re: Create

    Well if you're taking a local scene then there is no need to have excessive overlapping since you can always go back and shoot again. Excessive overlapping will tend to increase the chance of a "roller coaster" pano if any of the frames are slightly off vertically (if one frame is slightly tilted, the next frame will continue with this slanting trend since it is stitched to the previous one). Luckily Hugin has built in features to correct this problem if it happens. I made more overlaps cos I don't think I will be going back there so it is better to be safe then sorry; any "roller coaster" problem can be corrected later.

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    Default Re: Create

    thanks megaweb! i will read up. =D
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    Default Re: Create

    I made more overlaps cos I don't think I will be going back there so it is better to be safe then sorry
    its true to be safe then sorry, that place seems to be so spectacular!!! woots~~
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  8. #28

    Default Re: Creating Pano

    Could someone pls enlighten me regarding "nodal points"? This is a more advanced topic that the pros emphasize is important. And using the normal tripod is not the right way to do panorama actually. But I notice no one here mentions it when they do panoramic shots. Is it important?

    Also, I don't understand one more thing... Every time I hear the advice about keeping exposure constant throughout the shoot by using a fixed value shutter speed and aperture so that the images do not appear brighter or darker which could cause stitching problems.

    But the scene's lighting is not fixed, ie some areas are brighter, eg where the sun is, and some are darker, eg in the shady area. Then if you use an exposure which is an average of the brightest and darkest areas, won't you get underexposure for the bright parts, and over exposure for the darker parts?

    I thought by allowing the camera to adjust the exposure itself for each image, you will get a middle grey tonality and hence you ensure a consistent exposure throughout? But apparently that's not the case.... ?

    Thanks guys...

  9. #29
    Moderator ziploc's Avatar
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    Default Re: Creating Pano

    Quote Originally Posted by Andreq View Post
    Could someone pls enlighten me regarding "nodal points"? This is a more advanced topic that the pros emphasize is important. And using the normal tripod is not the right way to do panorama actually. But I notice no one here mentions it when they do panoramic shots. Is it important?

    Also, I don't understand one more thing... Every time I hear the advice about keeping exposure constant throughout the shoot by using a fixed value shutter speed and aperture so that the images do not appear brighter or darker which could cause stitching problems.

    But the scene's lighting is not fixed, ie some areas are brighter, eg where the sun is, and some are darker, eg in the shady area. Then if you use an exposure which is an average of the brightest and darkest areas, won't you get underexposure for the bright parts, and over exposure for the darker parts?

    I thought by allowing the camera to adjust the exposure itself for each image, you will get a middle grey tonality and hence you ensure a consistent exposure throughout? But apparently that's not the case.... ?

    Thanks guys...
    Hi Andreq,

    The nodal point is actually on the lens and not at the tripod mounting place (focal plane), so that when you turn the camera it is centered on the lens and not the focal plane, to avoid parallax error which would need correction later. But for very far objects, this is not so critical.

    As for the exposure, the reason of locking exposure is that, without it the camera will expose the scene to 18% gray (mid tone). So for brighter area, it will end up darker (the camera will try to dim the brighter scene to 18% gray) while the darker area will end up lighter (the camera tries to brighten it). So you end up having mid tone frames for all frames, but in actual fact, you should have bright frames for the brighter areas, and darker frames for the darker areas. This will result in unmatching tone when the frames are stitched together. By locking exposure, yes some areas will be over exposed and some under, but that is what it is supposed to be. This is one area where the Fuji S5 pro will do better since it has more dynamic range to compensate for the difference.

  10. #30
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    Default Re: Creating Pano

    ziploc has already explain about "nodal point"

    if you have let camera decide exposure and WB for you when doing multiple images for panoramic.
    you may end up with different exposure (brightness) and WB (color) images which unable to merge them seamless together.

    anyway, you can do a layer mask to brighten or darken certain part of images once you have put all images together.
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  11. #31
    Moderator ziploc's Avatar
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    Default Re: Creating Pano

    See the pic below to have an idea how the pano would look like without locking exposure. This pano was taken with my Fuji F11, and there is no manual exposure nor AE lock, so I could not lock the exposure. I've actually spent a lot of time correcting the tone before stitching, but as you can see below there are still obvious tone transition between some frames (highlighted by the red lines).



    For an illustration of the parallax issue, check out the pics on SmartBlend webpage:

    http://wiki.panotools.org/SmartBlend
    Last edited by ziploc; 29th January 2008 at 12:53 AM.

  12. #32
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    Default Re: Creating Pano

    Quote Originally Posted by twinkleS View Post
    Hi,

    any CSers here care to share how to piece up pictures into a paranomic form in photoshop?

    i can't seemed to google it. i really appreciate if anyone can share it with me.

    Lotsa ,
    twinkles
    try this http://************/2t62nf

  13. #33

    Default Re: Creating Pano

    Thanks ziploc and catchlights for explaining... May I ask some more questions...

    About the exposure part... I'm still not quite sure. I don't mean use the Auto exposure in camera. We know how off the exposure could be since the camer turns everything it sees to 18% grey. That will indeed make all the shots come out with wrong and different exposures.

    But I also don't see how by keeping exposure fixed throughout, we won't get different exposure for every shot. Maybe if I give some numbers as eg it will be clearer. Suppose aperture is fixed, the shutter speed for a proper exposure would be for:

    The brightest part 1/400, darkest part 1/100. So I set an average shutter speed of 1/200 throughout my panoramic shoot.

    Most shots will appear ok, but the brightest part will be overexposed by 1 stop, while the darkest part will be underexposed by 1 stop. This method in itself will yield different exposures already! Wouldn't this cause problems during stitching?

    My question is: Why can't we change the exposures manually when we encounter bright or dark areas? For eg, when I encounter the bright area, I will manually change the shutter speed to 1/400 instead of letting it fixed at 1/200.

    I have tried using a fixed exposure all the way and I noticed some of the buildings under bright sunlight are overexposed simply bcos I stuck to a single exposure setting in all my images. I'm wondering, shouldn't I change the exposure manually for each image if necessary?

    I hope you all get what I'm trying to say....

    And for the nodal point thingy, oh, so it's only critical if the subject is close to the cam? How do we maintain rotation about the lens instead of the camera base? I understand there are special pano tripod heads to do this but seems like never seen them sold here. Also expensive?

    Thanks....

  14. #34
    Moderator ziploc's Avatar
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    Default Re: Creating Pano

    Ok let's use your example that the brightest part is 1/400s and darkest part 1/100s. Now let's say you're taking a 3 frames pano with a large boulder below a blue sky, with the sun to the right and a huge tree casting shadow on the left. Let's say the boulder is very large that it spans from edge to edge of this pano, and our main subject is at the center. Now when you pan your camera, you'll notice that the left frame is 1/100s since the shadow of the tree is dark. Similarly right frame is 1/400s since the sun is bright.

    Assume that we do not lock exposure, so the left frame is exposed with 1/100s while the right frame 1/400s. Let's assume the middle frame is 1/200s. But now what happened to the boulder? It is being exposed longer and hence brighter in the left frame, but shorter and darker on the right. When you stitch the 3 frames, the boulder will not blend well due to tonal difference.

    The actual case will be more complicated then this when the camera uses evaluative metering. The camera checks the entire scene and chooses an exposure according to the sensor array and the data from its database. Any subtle changes in the scene will cause the exposure to be different. So this will result not only the boulder having tonal difference but also the sky, etc.

    Now let's say we lock the exposure, and take the exposure from the middle frame, which is 1/200s. The middle frame will expose correctly and that's great, since our main subject is in this frame. The left frame is 1 stop under, but that is ok because the tree is supposed to be darker comparing to the main subject. Same thing for the right frame, which will be 1 stop brighter. In all these 3 frames, the boulder (and the sky) will have consistent tone, so when stitching they will blend well together.
    Last edited by ziploc; 30th January 2008 at 01:47 AM. Reason: correct typos

  15. #35

    Default Re: Creating Pano

    Thanks ziploc, for making the explanation clearer. I see your point.

    Ok, to put it another way, and using the eg you've given about the 3 images, am I correct to say:

    Actually, on their own, the left image will not look good cos it is underexposed, and the right image is overexposed. (In other words, if you are not doing any panoramic shooting, you'll not set such exposures at all.) But RELATIVE to the center shot, the over and under exposure are acceptable cos we EXPECT the shadow to be darker anyway and the right side to be brighter.

    But I do foresee a slight problem.... What if the dynamic range of the scene is much larger?
    (And assume there is no huge expanse of boulder like the eg you mentioned earlier, ie every frame is important on its own.)

    The fake eg we've given is only +/- 1 stop diff either way, or 2 stops in TOTAL. What if there is a TOTAL diff of say 6 stops? Won't the bright areas be quite "burnt out" and the dark areas very much darker if we simply use an average exposure?

    I didn't do any panoramic shot on a particular overseas trip, but I remember I did notice the sky on one side looks a paler and brighter blue (where the sun was) while the side away from the sun looks more saturated. I thought that might be a little tricky for panoramas. Do we still choose an average exposure in this case between the darkest and brightest exposures?

    Sorry don't mean to complicate matters but just wish to be prepared the next time I encounter such a case.

    Thanks as usual.

  16. #36

    Default Re: Creating Pano

    Andreq,

    Taking panoramic photography is no different in exposure to normal photography. For better exposure, choose a situation when there is less exposure different e.g 1st and last light. Other time, try the mid tone technique so as to give you the best effect. Of couse, there is a great tool called photoshop to assist and help you to adjust the exposure.

    Try this photoshop tip
    Last edited by megaweb; 29th January 2008 at 09:57 PM.
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  17. #37
    Moderator ziploc's Avatar
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    Default Re: Creating Pano

    Quote Originally Posted by Andreq View Post
    Actually, on their own, the left image will not look good cos it is underexposed, and the right image is overexposed. (In other words, if you are not doing any panoramic shooting, you'll not set such exposures at all.) But RELATIVE to the center shot, the over and under exposure are acceptable cos we EXPECT the shadow to be darker anyway and the right side to be brighter.
    Let us recall that for most CCD sensors, the dynamic range is about 4 stops. So this gives you +2 stops over and -2 stops under the metered exposure (the camera shifts the mid point and that's why it is called "dynamic" range). As long as the darkest object in the darker frame or brightest object in the brighter frame are within this +/-2 stops range, they are not overexposed nor underexposed, and all details will be preserved.

    Quote Originally Posted by Andreq View Post
    But I do foresee a slight problem.... What if the dynamic range of the scene is much larger?
    (And assume there is no huge expanse of boulder like the eg you mentioned earlier, ie every frame is important on its own.)

    The fake eg we've given is only +/- 1 stop diff either way, or 2 stops in TOTAL. What if there is a TOTAL diff of say 6 stops? Won't the bright areas be quite "burnt out" and the dark areas very much darker if we simply use an average exposure?
    If the scene has an exposure range of more then 4 stops (or 6 stops for S5 pro), then yes clipping will occur. In this case there will be areas that are overexposed or underexposed. But as Megaweb already answered this will also occur when taking normal, non pano pics. The trick is to pick the right time when the exposure range is not that wide. If there's no choice (e.g. during travel), then we'll need to make a compromise by either taking the average exposure, or pick the exposure for the main subject as mentioned in the previous posts.

    One very simple way of understanding this is that the pano is simply one large shot, except that now it is so big that we need to split it into smaller pieces when shooting and stitch them back together later. Just as a single normal shot where there is only one exposure setting across the entire frame, the same applies to pano. This is the same for dynamic range as well.
    Last edited by ziploc; 30th January 2008 at 12:44 AM. Reason: add explanations

  18. #38
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    Default Re: Creating Pano

    wa.... this is getting so chim chim chim... @_@
    :heart: passion for photography!

  19. #39
    Senior Member AxeLa's Avatar
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    Default Re: Creating Pano

    Quote Originally Posted by twinkleS View Post
    wa.... this is getting so chim chim chim... @_@
    No sample pics??
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  20. #40
    Moderator ziploc's Avatar
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    Default Re: Creating Pano

    Quote Originally Posted by twinkleS View Post
    wa.... this is getting so chim chim chim... @_@
    Just ignore the technical discussions, those details are good to know but not needed.

    Btw, someone posted your portrait here.

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