Stitching as opposed to shooting larger format, revisited

<p>Before I plunk $ for a pano head, I need to know whether I can completely eliminate warp in stitched architectural interior shots (e.g., a living room scene). I was told on another forum that you'll always get some residual warping, that can't be removed. Edward Ingold, in a thread here last Nov stated: "Distortion is removed by converting each image to a spherical projection, blending, then reverting the assembled results to a rectilinear image. That's pretty straightforward in PTGui, especially if you determine the nodal point accurately." This sounds to me that, doing it correctly, you actually may be able to remove all the warping. Is this true? Like the original poster, I want to stitch frames together to get higher res with this type of subject, but can't have any warping. (Assume rotating on NPP axis.)</p>

 

<p>While you might remove warping, you will not remove perspective shifts from moving the lens. So, if you want a more "true" looking image, you either need to use large format or use a stitching system based off of a large format. I started a thread on building a system based off of large format a few weeks ago. There was a bit of a lively debate about the whole perspective shit thing. Well worth the read.</p>

<p><a href="../large-format-photography-forum/00YOcm">http://www.photo.net/large-format-photography-forum/00YOcm</a></p>

<p>In the end, I am on hold until I come up with a system to move the camera around the back without moving the back itself. I may actually build it right into a field camera. Although, composing could become an issue.</p>

<p>What is the widest angle lens you have right now and what size camera format?</p>

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<p>the whole perspective shit thing</p>

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<p>No wonder the discussion was lively. I'm not familiar with this technique myself. JR</p>

<p>duplicate deleted.</p>

<p>I have had success using lenses with shift capability, particularly the Canon TS-E lenses. I shift the lens outward and make an exposure at click stop. Using PTGui (I recently upgraded to the most current version PTGui Pro) for sttchign the iamges to gether I export as a "Blended + Layers" PSD.</p>

<p>I then open the image in Photoshop and if there are any glitches find the best layer that addresses the issue, and edit that layer's mask by painting with white to resolve the problem. The photo accompanying this post is an example of that approach. There were two glitches in the lower right corner tha tneeded to be resolved.</p>

<p>I also have a full Really Right Stuff panoramic rig ( A PC-1 rotating clamp, CB-10 bar, PG-02VA and clamp, and MPR-192 "nodal slide") . When you start trying to take in an extremely wide angle of view ,defining extreme as over 110˚. of a three dimensional scene and reduce in down to a two dimensional form there are going to be distortions that result from the resulting geometry of rendering such an extremely wide view in 2D . You just have to decide which type of distortion works best or least offensively for the photo you are making.</p>

<p>I had not seen Edward's technique discussed before and will try it. Do you have a link to that discussion? </p><div></div>

<p>this is a view from a single frame that was used to create the above composite. Yes it renders perspective differently that the final composite, but keep in mind that it is a much narrower angle of view.</p><div></div>

<p>"I had not seen Edward's technique discussed before and will try it. Do you have a link to that discussion?"<br>

Ans.: ref post is last on this page:<br>

<a href="00Xb8I">http://www.photo.net/digital-darkroom-forum/00Xb8I</a></p>

 

<p>"What is the widest angle lens you have right now and what size camera format?"<br>

Ans: FF Dslr, 20mm lens.</p>

 

 

<p>PTgui will take out any warping and lens distortions. Once you have your photos to stitch you can choose what direction you want the image viewed from. You can get the same corrections that a view camera does when it shift the lens.<br>

So take this for a case<br>

<img src="http://sewcon.com/photos/stitched/photo1.jpg" alt="" width="700" height="353" /></p>

<p>That is an exterm wide angle view, but I can stitch it any number of ways, as follows<br>

<img src="http://sewcon.com/photos/stitched/photo2.jpg" alt="" width="700" height="587" /></p>

<p><img src="http://sewcon.com/photos/stitched/photo3.jpg" alt="" width="700" height="587" /><br>

<img src="http://sewcon.com/photos/stitched/photo4.jpg" alt="" width="700" height="587" /><br>

<img src="http://sewcon.com/photos/stitched/photo5.jpg" alt="" width="700" height="587" /></p>

<p>Those are all made up from the same soure images, just stitched pointing diferent angles</p>

<p>Would you guys still buy PTGui Pro over the built in CS5 ability?</p>

<p>PhotoMerge in Photoshop CS5 is very good. But primarily I use PTGui Pro. That doesn't mean you should or that PhotoMerge is inadequate for the stitching you will be doing. </p>

<p>Thanks, Ellis. I used to use third party but CS5 has been fantastic. So much so, that I haven't even used my kaidan head for sometime now.</p>

<p>What type of subjects and what kind of light ( dim, mid day, etc.)?</p>

<p>I find that the more spatially elaborate the subject is in term s of near far relationships, the greater depth of field , the greater the depth of field required, the more stringent the need for keeping things level, and the larger the ultimate usage might be, the heavier duty the tools (cameras, lenses, hardware and software) are required. There are some pansI'll make with the camera handheld as well but for most of the work I am doing I am glad to have a good kit of tools at hand.</p>

<p>Is anyone using the Gigapan system? If so how does it rate with other pano-stitching methods and software.</p>

<p>I have access to one but unfortunately the weather has prevented me from testing with it.</p>

<p>FWIW, I will be using a Canon G10 but the DSLR Gigapan models also interest me.</p>

<p>Ellis, nothing specific these days and usually always while I'm just out snapping for snaps sake and finding myself making a pano or two in hand-held light. I'm really pleased with the results just from spinning on my heals so to speak. But years ago, we used to make vrml's and also used autostitch (i think it was called?) and PTGui. I still have the head but haven't used it in ages, since like CS3 era.</p>

<p>To echo donald, I'm looking at getting panopro giga also. Does anyone have any insight into how it stacks up?</p>

 

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<p>Is anyone using the Gigapan system? If so how does it rate with other pano-stitching methods and software.</p>

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<p>I've been using a Gigapan for a few years now (I enrolled in their beta program early on.) I can say only good things about the robotics approach. It enables a far, far superior image capture workflow than what is practical with any manual pano head.</p>

<p>At each slew position, I usually set the camera to take around 12 exposures spaced 1/2 or 2/3 stops apart. The pano circuit often is set for greater than 180deg (sometimes a full 360deg) field of view. </p>

<p>The point is to enable maximum freedom in choice of exposure and composition by deferring those decisions all the way to post. The typical print for me thus usually arises out of a subset of the slew circuit, and blends of a portion of each exposure stack.</p>

<p>The ideal camera for the Gigapan is actually a high pixel count compact digicam, not a DSLR. Exposure blending makes non-issues of the noisier and narrower dynamic range handicaps inherent of the smaller digicam imager. The gain of a smaller, lighter, more portable photography kit is a significant advantage.</p>

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<p>No wonder the discussion was lively. I'm not familiar with this technique myself. JR</p>

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<p>Jeez Jeremy, so I missed an "F" key somewhere.....</p>

<p>Scott, I think Pano heads+ ptgui works great on single rows, but as soon as you start multi rows you start to see perspective shifts. There is just no way around it because the source images are collecting a different perspective.</p>

<p>That all said, Single row + WA would probably work just fine for the OP. Sounds like he is going for illustrative and wide rather than massive print.</p>

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<p>... but as soon as you start multi rows you start to see perspective shifts.</p>

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<p>Perspective shift? Do you mean perspective distortion, the kind commonly compensated for with movements with a large format camera?</p>

<p>In general, this compensation is really easy to replicate in post (via essentially the same transforms actually.) However, a side-effect of the digital domain warping operation is that it spatially compresses and expands local areas of the image. The potential problem then with single frame captures is running out of pixels, i.e., lose too much detail in sections of aggressive expansion.</p>

<p>This highlights a key advantage of working with high resolution composites (and by implication, the robotic mounts that make the workflow practical.) If for example you have enough pixels to place 1200 real dpi onto a 16x20 print, what it really says then is that you can afford to lose up to 900 of those dpi to filtering operations, and still get a tack sharp super-detailed print.</p>

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<p>Now here's the perspective "corrected" version.</p><div></div>

 

<p>Nope, I am talking about actual perspective shifts that happen from the movement of the front element. Take a window, for instance. From one angle, you can see the left side of it's casing, but not the right. As you move your lens, you can now see both the left and right, and then finally just the right. The severity of this increases with the wider of an arc you make. 90% of people, I would guess, would never notice this, but it bugs me to a degree.</p>

 

<p>Zach, the camera is rotated around its entrance pupil, so there is no shift of perspective as you describe it. </p>

<p>I do multi row stitching all the time, typically 3 row x 8 to 10 columns, there is no problem with perspective at all. </p>

<p>Scott, it would be impossible not to have it. You are using a curved field of capture (akin to a fisheye and some ultrawides) vs a flat plane of capture. Not to mention the total size of the arc is going to determine how much you see the effect. a 3x8 with a 200mm will show it much less than a 3x8 with a 14mm. If it didn't have this effect, it would be 100% impossible to do a 360 panorama, or even a 180.</p>

<p>Zach, you really don't konw what you are talking about here, sorry.</p>

<p>Scott, It is elementary physics. Sorry, but if you were looking straight forward, with a single plane, you can't see what is to your side. You have to turn to see that. You are changing your entire viewpoint. Even if your entrance pupil is constant, you are changing where/how you interact with that pupil. To not have this distortion, both the entrance pupil and the front element would have to stay constant since they control the projection to the film plane.</p>

<p>Maybe perspective is the wrong term, but is still a distortion.</p>