Blur near nadir

[Josip Posavec]

Any idea why images near nadir are sometimes blurred on some part? How to avoid this?

[UtahBob]

On Thursday, June 4, 2015 at 11:50:12 AM UTC-4, Josip Posavec wrote:

Any idea why images near nadir are sometimes blurred on some part? How to avoid this?

Josip,

This is generally the result of the difference in center verses edge sharpness of the lens.  For you horizon images - say four around, the nadir portion is captured with the edge of the lens while the nadir image is captured with the center of the lens.  I see this on almost every stitch but some it is more noticeable than others.

So to fix, one method is to capture more nadir with your horizon images.  I go -15 with 8mm lens.  So the transition between the horizon and nadir image will be less when stitched.   Better method is to mask the nadir in a way that the difference is less noticeable such as along a tile seam, carpet edge, etc.  This can be done in PTGui using the masks or in PS perhaps using layers (but playing with nadir is tricky).  Another way is to blur the nadir image a bit after having the stitch complete and then replacing the nadir image with the one blurred.

The more calibrated your head and the better your alignment of the nadir the easier it should be to fix.

In the image you posted (by the way, add images in the future using a hosting site such as ge.tt, rather than posting directly), it seems as if the nadir image as matched to another image that is at a 90 degree angle.  Texture is off by 90 degrees unless this is just an artifact in the image from the blur and compression.

[Josip Posavec]

Thank you for your explanation.

Next week I have to do 60 pano tour with real nadirs (its outdoor Floor Tiles showroom - for them nadir is the most important part of 360 image). 

I have Nodal nadir adapter.

So, all I can do is to crop images as much as possible to not use bottom edge of lens and use more nadir image?

--
--
You received this message because you are subscribed to the Google Groups "PTGui" group.
To post to this group, send email to pt...@googlegroups.com
To unsubscribe from this group, send email to ptgui+un...@googlegroups.com
Please do not add attachments to your posts; instead upload your files at a file sharing site (for example http://ge.tt/ ) and include a link in your message.
For more options, visit this group at http://groups.google.com/group/ptgui

---
You received this message because you are subscribed to the Google Groups "PTGui Support" group.
To unsubscribe from this group and stop receiving emails from it, send an email to ptgui+un...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[UtahBob]

On Thursday, June 4, 2015 at 2:08:37 PM UTC-4, Josip Posavec wrote:

Thank you for your explanation.

Next week I have to do 60 pano tour with real nadirs (its outdoor Floor Tiles showroom - for them nadir is the most important part of 360 image). 

I have Nodal nadir adapter.

So, all I can do is to crop images as much as possible to not use bottom edge of lens and use more nadir image?

Good that you have the nadir adapter to keep the height the same and get most out of viewpoint correction.

Because the nadir is very important in your next shoot, I would do some tests to see what is the optimal angle for the horizon shots in order for the lens clarity to match the nadir clarity.  There is no reason why you can not use more than one nadir and angle the nadir image above -90.  So you could take four nadir at some angle perhaps -55.  Viewpoint correction for all four as usually done for a nadir but also a lot of masking.    It will depend on how much sharpness falloff there is from the center as to where to set the angles.

Cropping as you suggest (masking) is one way but maybe adjusting capture images might be another.  Definitely figure it out ahead of time.  60 is a lot to fix.

One other option is to reduce the amount of zoom available in the final tour images so any differences are not as noticeable.

[Josip Posavec]

What about different blend option and interpolator? Can this make any difference in blending nadir?

[UtahBob]

On Thursday, June 4, 2015 at 3:14:46 PM UTC-4, Josip Posavec wrote:

What about different blend option and interpolator? Can this make any difference in blending nadir?

I just tried sharp verses soft on some grass nadir blur but that is different from tile.  The difference is very slight but it seemed as if sharp was less noticeable transition.  You'd have to try it with an image of yours.  I don't think the interpolator will make a difference since you'd be using one interpolator against all the images but I'm not sure.

Have you thought about using Smartblend to try and see if the seams orient better?

 

[John Houghton]

On Thursday, June 4, 2015 at 7:08:37 PM UTC+1, Josip Posavec wrote:

Thank you for your explanation.

Next week I have to do 60 pano tour with real nadirs (its outdoor Floor Tiles showroom - for them nadir is the most important part of 360 image).

Josip, For maximum quality at the nadir, you can take two nadir shots with the camera pointing down (pitch -90), rotating the head around through 90 degrees between them.  The viewpoint nadir will then blend in perfectly, and the two nadir shots should also blend in with the horizontal row very well too.

John

[Josip Posavec]

John, can you explain more about this two nadir shots (or just send me picture)?

If I have 2 nadir shots, how to combine them in PTgui?

I feel that this can be solution for my problem, but I don't understand it completely.

THANK YOU!

--

[PTGui Support]

Hi Josip,

You can add as many nadir (or other) images as you want, just load
everything in PTGui and it should figure out how things overlap.

You can use Masking in PTGui Pro to tell the blender which parts of
which images you want to keep. Use Viewpoint Correction on the nadir
images if they haven't been taken from exactly the same viewpoint.

Lastly, don't crop your images as you suggested earlier; this changes
the effective focal length. Instead use masking, or make unwanted parts
transparent.

Kind regards,

New House Internet Services BV
Joost Nieuwenhuijse

-----------------------------------------------
PTGui - Photo Stitching Software

www.ptgui.com
For support see: http://www.ptgui.com/faq/
-----------------------------------------------

> <mailto:pt...@googlegroups.com>

> To unsubscribe from this group, send email to
> ptgui+un...@googlegroups.com

> <mailto:ptgui%2Bunsu...@googlegroups.com>

> Please do not add attachments to your posts; instead upload your
> files at a file sharing site (for example http://ge.tt/ ) and
> include a link in your message.
> For more options, visit this group at
> http://groups.google.com/group/ptgui
>
> ---
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it,
> send an email to ptgui+un...@googlegroups.com

> <mailto:ptgui+un...@googlegroups.com>.

> For more options, visit https://groups.google.com/d/optout.
>
>

> --
> --
> You received this message because you are subscribed to the Google
> Groups "PTGui" group.
> To post to this group, send email to pt...@googlegroups.com
> To unsubscribe from this group, send email to
> ptgui+un...@googlegroups.com
> Please do not add attachments to your posts; instead upload your files
> at a file sharing site (for example http://ge.tt/ ) and include a link
> in your message.
> For more options, visit this group at http://groups.google.com/group/ptgui
>
> ---
> You received this message because you are subscribed to the Google
> Groups "PTGui Support" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to ptgui+un...@googlegroups.com

> <mailto:ptgui+un...@googlegroups.com>.

[Josip Posavec]

It will be long testing weekend...

Thank you Joost!

[John Houghton]

On Friday, June 5, 2015 at 10:38:33 AM UTC+1, Josip Posavec wrote:

John, can you explain more about this two nadir shots (or just send me picture)?

Here are two nadir shots from a panorama, taken with the camera pointing directly down with the head rotated around through 90 degrees between them. 

http://ge.tt/2dQj8mH2

The image on the right shows the two shots overlaid with the tripod and head masked from each of the shots.  The net result is maximum coverage of the nadir area using the centre part of the images and therefore best quality.  Masking is also needed to cope with tripod shadows, but that's another story.  BTW, for consistency it is best to turn off the auto rotate feature in the camera as the orientation sensor gives random values when the camera is pointed straight up or down.  The images need to be in the same orientation as supplied to PTGui so that they all have the same angle of view.

If I have 2 nadir shots, how to combine them in PTgui?

As Joost says, just add them to the project along with the rest of the images and ensure that there are control points between them.  The masks should prevent control points being generated on parts of the tripod and head, which would otherwise cause alignment problems.  If you want to help the optimizer, you can initialise the pitch of the nadir images to -90 on the Image Parameters tab.

John

[Josip Posavec]

Thank you John. Now I understand, but I can not do it on this way because I have Ultimate R10 Head + nodal adapter.

Tomorrow I will get tripod with horizontal pole option and will test it.

But now I know what is goal. Just will have to find the way my HW can do it.

Thank you!

--