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shim
3/14
Shim
Updated on December 17, 2016

How to choose a lens to make a virtual tour?

Now that you know how many photos you want to shoot for what final quality, you only have to choose your ideal lens. Here are a few elements of choice...

Objectif Canon 8-15 mm fish-eyeWhen we start talking about the choice of lens, we think firstly and right away about its optical quality. It is of course very important, but it's also clear that other points need to be taken into account.
Some of them, like the quality and the "beauty" of the beams are completely subjective but others, like the quality and the stitching quality, a lot more "objective". But all lenses are not equal on this criteria. 10.5 mm Nikkor and 8-15 mm Canon fisheye are the best on this last criteria. And despite a widespread prejudice, 14 mm Canon and Nikkor are a lot more complicated to stitch correctly...
The cheap Samyang 8 mm here on the right for APS-C sensor can become an excellent and cheap alternative. Here is typically an unattractive lens if not for the price, unbeatable, but it stitches very well and its optical quality gets way better if you're working in RAW...

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Lens quality, optical distortions, etc...

One very surprising fact is that the panoramic photographer tries to stitch together the worst parts of the images: their edges! It is the basic principle of panorama by stitching, but it's indeed where all the defects of a lens are gathered:

  • Vignetting, sometimes a big defect;
  • Chromaticism;
  • Loss of sharpness in comparison with the center of the photo and above all...
  • Distortions, more complicated and even, in certain cases, impossible to fix, in addition to the fisheye distortion.

In addition to the shape of the beams created when you're shooting a light source directly...

Optical quality

Almost all lenses on the market are at least good nowadays. Some, of course, are excellent, and it's very important in panoramic photography. Regarding virtual tour creation, I wouldn't be so sure. A good lens is enough. Most of the time, you'll work with a very closed diaphragm to have a maximum depth of field and you'll then see appear diffraction effects, meaning a slight loss of sharpness. (It's not that bad because it can be fixed with an over-accentuation). Even the Samyang, once over-accentuated, is full of surprises but you need to accentuate it more than a Canon or Nikkor, it's true.

Here is the result of my tests in a recapitulative table...


Recapitulative table of fisheye lenses

 
Lenses
Distortions/Easiness of stitching Price
 
Nikkor 10.5 mm FE
******
$650
 
Nikkor 16 mm FE
*****
$750
 
Canon 15 mm FE
*****
SE
 
Canon 8-15 mm FE
******
$1,300
 
Sigma 4.5 mm FE
****
$900
   
Sigma 8 mm FE
****
$900
   
Sigma 15 mm FE
****
$600
   
Samyang 8 mm FE
*****
$300

 

 

 

 

 

 

Recapitulative table of short focal lenses

 
Lenses
Distortions/Easiness of stitching Price
 
Nikkor 10-24 mm DX
***
$1,000
 
Nikkor 14-24 mm
***
$2,000
 
Nikkor 14 mm
**
$1,400
 
Canon 14 mm II
**
$2,200
 
Sigma 10-20 mm DG
***
$650
   
Sigma 12-24 mm DG
***
$875
   
Tamron 10-24 mm Di II
***
$500
   
Samyang 14 mm
**
$400
         

 

 

 

 

 

 

 

 

Optical distortions

distorsions à l'assemblageAlmost all images distort the images. Except in architecture photography, it is seldom a problem. However, when you're stitching photos together, it can quickly become annoying because the stitching is not perfect then, as you can see in the example here. This defect of the lens materializes by an imperfect alignment of the two photos. Even if you might be tempted to blame it on the setting of the entrance pupil, it is in fact often due to another defect, viciously hidden in the lens formula: distortions. It is so important in panorama by stitching that I dedicated an entire page to it.
When the lens has lots of optical distortions, it often happens to see straight lines stitchings, especially, imperfect with most stitching software. Straight lines don't overlap perfectly. It is then necessary to perform edits in Photoshop after stitching. It is maybe even more essential in virtual tour creation because you're stitching photos taken in all directions. The less residual distortions your lens has (well-hidden behind the big distortion due to the optical formula of the fisheye lens!), the more perfect your stitching will be on first try, with no need for further edits.
You can imagine that all lenses aren't equal when it comes to distortions and there are lenses of all kinds! From very sharp and very distorted to very sharp and not so distorted, and even pretty good and not too distorted, etc.

My recommendation: I prefer a little bit less sharp lens but without distortions because I know that the stitching will be good on first try!


Remarks about lenses distortions

Thanks to my experience of trainings which made me see numerous pairs camera/lens - Canon, Nikon, Sigma, Tamron, Samyang mostly -, I now know that it is impossible to evaluate a priori if a lens or zoom lens will stitch correctly. There are several cases, themselves depending a lot on the stitching software:

A - The lens doesn't have distortions or it has distortions, but they're easy to correct directly in the stitching software. There's no need to prepare the photos before stitching. The panorama is then often perfect without needing further edits.
B - The lens has distortions that don't stitch well directly but that do once corrected with Lens Correction of Camera Raw or Lightroom for instance, before stitching. The image stitched seldom requires edits in Photoshop or they're very easy to perform. Most common case...
Cassure de lignesC - The lens has moustache distortions, the most vicious, and whether they're corrected or not before stitching doesn't make much of a difference most of the time. The final stitching shows numerous stitching artefacts - in the form of breaks in the lines for instance, as shown in the illustration above -. Even with a multilayer rendering in Photoshop, it is sometimes very complicated to "fix" the panorama. In this last case, I "strongly" advise my trainees to change lens to make virtual tours often. (Caution: good news! There's change from version of Autopano Giga 3.7...)

Note! A very sharp lens, good for classic photography, can be very bad for image stitching.

Thanks to this same experience, I know that you should absolutely try the lens of your dreams before buying it if you want to use it to make panoramas by stitching regularly. No, there's no rule! No, fixed lenses are not always better than zoom lenses - about distortions, may I remind you -. No, lenses of big brands are not always better than multiclip ones, still regarding the only criteria that matters here: optical distortions.


I thus think that the nature of the distortions of a lens is the key point to watch when you want to make lors of panoramas by stitching. It is true that it becomes less of a problem from version of Autopano Giga 3.7. Indeed, not all photographers realize that it's the main cause of failure when stitching a panorama, unlike the entrance pupil, which in the case of no foreground, won't really matter. If your stitchings are not perfect, look into your lenses rather than the settings of your panoramic head!top

 

 


Beams on light sources

When shooting indoors, a detail often draws my attention: beams! That's what gives a starry aspect to our punctual light sources. Their shape depends on the number of blades into the diaphragm, of their thickness and their position in the lens. They're thus more or less numerous and aesthetic, according to me.



Number of blades, Bokeh and beams...

Nowadays, the engineer who needs to choose an optical formula and the construction of his new lens must face a dilemma - no more, no less! Either he puts lots of blades in his diaphragm (from 9) and the lens will offer a nice Bokeh which means a nice middle ground blur, even when the diaphragm is shut. (Bokeh in full opening is always more beautiful because the diaphragm is completely open, thus circular by definition.) Or he decreases this number to 7 or 8 and the lens will offer nice beams, not too numerous, on punctual light sources, but detrimental to a nice bokeh. Blurs or beams? Your call!

AigrettesBokeh

Read my article about beams on my blog (in french) suivre

Here are a few examples gathered during my training sessions...

All these photos have been shot with the same diaphragm, F11.0.



Aigrettes du Nikkor 10,5mm Fish Eye   Aigrettes du Nikkor 16mm Fish Eye
     
Aigrettes du Canon 15mm Fish Eye   Aigrettes du Canon 8-15mm Fish Eye
     
Aigrettes du Sigma 8mm Fish Eye   Aigrettes du Sigma 15mm Fish Eye
     
Aigrettes du Samyang 8mm Fish Eye  
     

pointilles

 

My recommendations to make a choice...

Very short orthoscopic focals (not fisheyes) are all very distorted nowadays because of aspheric lenses in the optical formulas and require to shoot at least two ranges of photos: I avoid them, even with PTGui or Autopano which can stitch them correctly.
fisheye lenses, as for themselves, stitch at least correctly and sometimes even perfectly. It's almost a challenge with images presenting such a level of deformation. Sure, but a deformation isn't a distortion!
As such, I'd like to mention the Nikkor 10.5mm DX for APS-C sensor, the 16 mm fisheye Nikkor for D800 or D610, the Canon 15 mm FE or the new 8-15 mm fisheye Canon for Canon 24 x 36 sensor. Those three lenses stand out regarding what's interesting us here, their distortions. Stitch a 180 x 360 ° panorama without stitching artefacts isn't exceptional with these lenses!

Two Fisheye lens very good and which assembles very well.

With other ones, there will be more or less stitching artefacts and sometimes really too many for someone who wants to make virtual tour regularly.
The last good surprise comes from the 8 mm Samyang for APS sensor. Indeed, for $300 (instead of 280 dollars now that it features a chip in order to save exposure automatisms), even if the optical quality doesn't reach the top, it is completely sufficient at F11 (accentuation really helps), the six beams on light sources are quite thin, the depth of field at F11 is real and the manual focusing is smooth, perfect to make our shot, for which we really don't need the autofocus. Its value for money is really unbelievable!
And finally, the D810 (or D4) + Nikkor 10.5 mm DX set, even if technically, it can be used, doesn't have any interest in practice, because the number of effective pixels is really very low, especially for the Nikon D4. Virtual tours are very small then...

 

In the next page, we'll detail my favorites lenses... Suivre


Next page 3bis/14 : my favorites lens suivre






     
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