Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Started Jan 23, 2013 | Discussions
Anders W Forum Pro • Posts: 21,468
Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
32

Just having received the Samyang (aka Rokinon) 7.5/3.5 fisheye, I couldn't resist the temptation to give it a spin yesterday just to see how it would compare for various purposes with the Panasonic 7-14/4 that I am used to shooting.

Sometimes the fisheye distortion actually adds to rather than detracts from the composition. At other times, however, all you want is the extremely wide angle. The image below, from the main building of Uppsala University, is, to my mind, an example of an image where the fisheye effect is more undesirable than desirable. On the other hand, defishing to the rectilinear projection (the one used by any ordinary lens) wouldn't work well because of the extreme stretching of the corners and edges it implies. The lack of resolution as well as the extreme distortion ("fattening") of objects close to the left and right edge looks horrible to my eyes.

Samyang 7.5/3.5 at f/5.6

But here, and in many other cases, the Panini projection comes to rescue. This is a projection that cannot be natively accomplished by any lens since it is not "azimuthal", i.e., not symmetric in all directions from the center. It keeps vertical lines straight along with all radial lines (lines that pass through the center). However, horizontal lines that aren't radial are still more or less bent. By making that concession, it avoids the extreme stretching of the left and right edge that the rectilinear projection implies when the FoV becomes sufficiently wide.

Samyang 7.5/3.5 after (partial) defishing to Panini

The image below shows the same scene as captured by the Panasonic 7-14 at 7 mm. Although the horizontal FoV is less than that of the fisheye (102 versus 132 degrees), the "fattening" of things at the edges is already obvious, e.g., the girl and the door at the left edge.

Panasonic 7-14/4 at f/4 and 7 mm

But just as you can (partly) defish a fisheye image to Panini, you can of course "refish" a rectilinear image to Panini as well. Here's what the "refished" image produced by the 7-14 looks like. As you can see, the girl and the door to the right have now regained far more natural proportions.

Panasonic 7-14/4 at f/4 and 7 mm after (partial) "refishing" to Panini

As you can see, the "refishing" of the rectilinear image to Panini implies a loss of vertical FoV in the center of the image. This can, if we want, be avoided by modifying the Panini projection by stretching it vertically at the edges. The same operation simultaneously makes horizontal lines less strongly bent at the upper and lower edge. The concession we make (there must always be one) is that radial lines are no longer straight, as illustrated by the image below.

Panasonic 7-14/4 at f/4 and 7 mm after "refishing" to modified Panini projection

Comments and questions of all kinds about the utility of UWAs and various projections (more than about the images as such, which are just meant to serve as modest examples) are of course welcome.



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Dennis Arendt Regular Member • Posts: 207
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
1

Please tell the forum what software you are doing these conversions with.Very interesting results and I do have both lenses you worked with.TIA

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OP Anders W Forum Pro • Posts: 21,468
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
7

Dennis Arendt wrote:

Please tell the forum what software you are doing these conversions with.Very interesting results and I do have both lenses you worked with.TIA

These were done with Hugin, which is a very powerful program and, on top of that, free of charge. You find more info here.

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nathanhw
nathanhw Regular Member • Posts: 250
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Cool.  I never thought to turn a non -fisheye image into a fisheye image, but you make a good case for it.  I'm often shooting at the wide end of the Oly 9-18 and sometimes the fattening is annoying.  You have educated me about a solution.

Are you doing this PP in Lightroom?

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OP Anders W Forum Pro • Posts: 21,468
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

nathanhw wrote:

Cool. I never thought to turn a non -fisheye image into a fisheye image, but you make a good case for it. I'm often shooting at the wide end of the Oly 9-18 and sometimes the fattening is annoying. You have educated me about a solution.

Thanks. The Panini projection is already pretty well known as a defishing solution. But like you, I sometimes find the "fattening" at the edges when shooting with the 7-14 very disturbing. Everything works nicely when you have a fairly flat target more or less parallel to the sensor, as in the image below. But when you are shooting down a hall or room, you often run into trouble, especially when there are things whose proportions are known or guessable towards the edges.

Tübingen, Stiftskirche

Are you doing this PP in Lightroom?

Only partly. In this case, the processing was done as follows:

1. Basic PP in LR, then export as full-size jpg (perhaps I should have used TIFF instead for best quality).

2. Import the jpg into Hugin, defish/refish, and export as TIFF.

3. Import the TIFF in LR, do final touch up of perspective distortion, export as jpg at final display size.

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Trevor Carpenter
Trevor Carpenter Forum Pro • Posts: 16,826
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
1

Good post with good explanation, thanks for posting. Personally I own a fish eye because i like the games I can play and no particular desire to defish

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OP Anders W Forum Pro • Posts: 21,468
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Trevor Carpenter wrote:

Good post with good explanation, thanks for posting. Personally I own a fish eye because i like the games I can play and no particular desire to defish

You are welcome Trevor. Personally, I like playing with the fisheye as a fisheye too. But sometimes the ability to defish it nevertheless comes in handy.

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RoelHendrickx
RoelHendrickx Forum Pro • Posts: 26,971
Interesting. View from a non-defisher. (IMGS)
1

For architecture indoor, I choose between the ZD7-14 and the ZD8mmFE depending on the circumstances.

That is because I generally don't de-fish (and certainly don't re-fish)

Buildings with many straight lines (like most modern buildings) are often served best with a rectilnear UWA (although not always, and there are possibiliteis of using FE as well).

Buildings with circular patterns (domes etc, often in older constructions, like churches and mosques), can IMHO actually be captured well with an non-de-fished fisheye.

Matter of taste also, probably.

Examples :

Istanbul (fisheye):

Courthouse (rectilinear):

The organic shapes of some post-modern buildings (like Gaudi's work or Hundertwasser) could probably be shot just as well with fisheye as rectilinear - who could tell the difference?

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OP Anders W Forum Pro • Posts: 21,468
Re: Interesting. View from a non-defisher. (IMGS)
1

RoelHendrickx wrote:

For architecture indoor, I choose between the ZD7-14 and the ZD8mmFE depending on the circumstances.

That is because I generally don't de-fish (and certainly don't re-fish)

Buildings with many straight lines (like most modern buildings) are often served best with a rectilnear UWA (although not always, and there are possibiliteis of using FE as well).

Buildings with circular patterns (domes etc, often in older constructions, like churches and mosques), can IMHO actually be captured well with an non-de-fished fisheye.

Matter of taste also, probably.

Examples :

Istanbul (fisheye):

Courthouse (rectilinear):

The organic shapes of some post-modern buildings (like Gaudi's work or Hundertwasser) could probably be shot just as well with fisheye as rectilinear - who could tell the difference?

No reason to disagree with anything you say about what usually goes best with what or with your illustrations of the points you make. What I say and show in my OP is that there are additional options besides the two you choose between: rectilinear projection and fisheye projection. The reason we have those particular two is that they are the only ones a lens a can natively produce and hence the only ones we could realistically use before the digital age. Now we have additional possibilites which for this or that scene might prove superior to the other two.

The general lesson here is that distortion (relative to the way our eyes see things) can never be avoided when we go wider than our eyes can in a single glance. But we can now choose between different kinds of distortion in a way that previously wasn't possible, and certain kinds of distortions can, in a specific case, be far less disturbing, or far more charming, than others.

Here's another illustration, a building with many straight lines (La Rocca in Spoleto, Umbria, Italy), caught with the Panasonic 7-14/4 at 7 mm. The rectilinear image looks like this ...

Panasonic 7-14/4 at f/5.6 and 7 mm

... and the "refished" (modified Panini) like this.



Panasonic 7-14/4 at f/5.6 and 7 mm, "refished" to modified Panini

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aimawayfromface Regular Member • Posts: 291
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Anders W wrote:

But here, and in many other cases, the Panini projection comes to rescue. This is a projection that cannot be natively accomplished by any lens since it is not "azimuthal", i.e., not symmetric in all directions from the center. It keeps vertical lines straight along with all radial lines (lines that pass through the center). However, horizontal lines that aren't radial are still more or less bent. By making that concession, it avoids the extreme stretching of the left and right edge that the rectilinear projection implies when the FoV becomes sufficiently wide.

I really like the Panini-processed 7.5 fisheye image much better than the 7mm. It makes me think about selling my 9-18 and getting the 7.5mm as my only wide angle lens, as I only use the 9-18 at 9mm and also don't like the "fattening" at the corners.

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OP Anders W Forum Pro • Posts: 21,468
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

aimawayfromface wrote:

Anders W wrote:

But here, and in many other cases, the Panini projection comes to rescue. This is a projection that cannot be natively accomplished by any lens since it is not "azimuthal", i.e., not symmetric in all directions from the center. It keeps vertical lines straight along with all radial lines (lines that pass through the center). However, horizontal lines that aren't radial are still more or less bent. By making that concession, it avoids the extreme stretching of the left and right edge that the rectilinear projection implies when the FoV becomes sufficiently wide.

I really like the Panini-processed 7.5 fisheye image much better than the 7mm. It makes me think about selling my 9-18 and getting the 7.5mm as my only wide angle lens, as I only use the 9-18 at 9mm and also don't like the "fattening" at the corners.

Well worth getting the Samyang/Rokinon 7.5. Very good lens for a very reasonable price. Not sure it's such a good idea to sell your 9-18 though. I have no plans of letting go of my 7-14. There are instances where the 7.5 may simply be too wide and where you'd have to crop (with loss of IQ) to get what you want. And as I exemplified, you can always Panini-process your 9-18 images too when you find the "fattening" at the corners disturbing.

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Keith Schmidt Veteran Member • Posts: 7,142
Great information! Thank you!
1

Looking forward to trying this out with my new 7.5mm rokinon.

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noirdesir Forum Pro • Posts: 13,732
A few questions on projections

Anders,

This reminds me of my trusty Horizon 202, a mechanical swing lens camera which quickly became my favourite camera when I got it in mid-nineties. The perspective was very unique and since it was in effect a small MF camera, it created, in the film era, a noticeable image quality gain (despite being fix-focus). I don't think the Panini projection quite matches it but it might be the closest I have seen so far in the digital age (its true digital equivalents are very expensive and rare), though stitching of large numbers of images should in principle be able to replicate it (as it is shown by the panorama mode of the iPhone).

The effect naturally varies a lot depending on the focal length used. My questions are:

- Do you know of a way to achieve the 'Horizon' projection digitally (I think the Panini projection gets there partly)?

- How does the Samyang 14 mm with its stereographic projection compare?

hifi
hifi Senior Member • Posts: 2,569
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
1

This is a great post - thanks for showing this!

I have the Pany fisheye and absolutely love it.  For most of my fisheye shots, I use the fisheye-hemi plugin.  It provides the most pleasing results to my eyes.  I also have PTLens but prefer the other plugin better.  I was originally going to get the Pany 7-14 but ended up with the fisheye instead (due to budget reasons), and glad I got the fisheye.

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Aleo Veuliah
MOD Aleo Veuliah Forum Pro • Posts: 14,758
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4
1

Good comparison. I still prefer the 7-14mm, but sometimes is nice to see the curves the fisheye lenses make.


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clengman
clengman Senior Member • Posts: 1,971
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Anders - Great examples! Thanks.

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OP Anders W Forum Pro • Posts: 21,468
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

hifi wrote:

This is a great post - thanks for showing this!

I have the Pany fisheye and absolutely love it. For most of my fisheye shots, I use the fisheye-hemi plugin. It provides the most pleasing results to my eyes. I also have PTLens but prefer the other plugin better. I was originally going to get the Pany 7-14 but ended up with the fisheye instead (due to budget reasons), and glad I got the fisheye.

You are welcome. Fisheye Hemi uses the Panini projection (though they don't mention that) so the defishing results I got for the first image in the OP would be practically the same as you would get. If you already have Photoshop, it is perhaps also the most expedient solution if it's just standard Panini you want. Just open the image in Photoshop, apply the projection "filter" and save the modified file. However, it is not as flexible as Hugin, which gives you a lot of control over exactly how to defish. Hugin also allows you to "refish" images show with a rectilinear lens, which may not be important to you since you decided to go with fisheye only, but may be to others.

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OP Anders W Forum Pro • Posts: 21,468
Re: A few questions on projections
1

noirdesir wrote:

Anders,

This reminds me of my trusty Horizon 202, a mechanical swing lens camera which quickly became my favourite camera when I got it in mid-nineties. The perspective was very unique and since it was in effect a small MF camera, it created, in the film era, a noticeable image quality gain (despite being fix-focus).

Hey, that's an interesting example. I hardly knew that such cameras existed. In-camera panorama stitching with film. That's something.

You of course know how the Horizon 202 works but here's a link for those who don't.

http://en.wikipedia.org/wiki/Panoramic_photography

You find a general description of the method under "Panoramic cameras and methods" including a link to Horizon that will tell you more about that particular camera.

I don't think the Panini projection quite matches it but it might be the closest I have seen so far in the digital age (its true digital equivalents are very expensive and rare), though stitching of large numbers of images should in principle be able to replicate it (as it is shown by the panorama mode of the iPhone).

I can't tell for sure either if it quite matches Panini but it's certainly close. What would you think might be the difference? And what would be the true digital equivalents that we could buy these days if we had a lot of money to spend?

The effect naturally varies a lot depending on the focal length used. My questions are:

- Do you know of a way to achieve the 'Horizon' projection digitally (I think the Panini projection gets there partly)?

I would guess that Panini for all practical purposes gets there. What I can see in your sample (and other samples I found for Horizon) is that it keeps vertical lines straight but bends horizontal lines unless they run through the center. My guess is that it also keeps radial lines straight, just like Panini.

- How does the Samyang 14 mm with its stereographic projection compare?

The only Samyang 14 mm I know about is a rectilinear WA (but with a barrel distortion of some five percent).

I think the lens you might have in mind is the Samyang 8 mm FE for APS-C DSLRs (which I know uses the stereographic projection) and/or the Samyang 8 mm FE for Sony NEX and Samsung NX (which I think uses it as well, although I am not perfectly sure).

The Samyang/Rokinon 7.5/3.5 for MFT, by contrast, uses the equal-area (also known as equisolid) projection, which is the projection used by most fisheye lenses. Stereographic projection is said to offer a slight advantage as long as you don't defish since its edge distortion is not quite as severe. On the other hand, defishing software usually assumes equal-area projection which presumably makes results from stereographic input less satisfying.

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mfj197
mfj197 Contributing Member • Posts: 525
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

Anders, very interesting and thanks for this.  I remember kenw's thread on defishing the Samyang a year ago or so (he created Lightroom lens profiles, although there were some limitations with that approach).  Would you be able to post edge and corner crops from the Panini projection please?  I'd like to see how much blurring takes place by stretching the corners so much - of course the Samyang is very sharp before the image manipulation.

I thoroughly enjoyed using the 7-14 whilst I had it but it was just rather big, which meant sometimes I didn't have it with me when out and about.  The Samyang is wonderfully small and is looking increasingly interesting to me!

Michael

duartix Veteran Member • Posts: 3,605
Re: Defishing and Refishing with the Samyang 7.5/3.5 and the Panasonic 7-14/4

I have the Samyang 7.5mm too.

I love it too.

I defish most of my photos to Panini too because I feel it's a lot more natural.

I use Hugin for that too.
I do it to video too.

http://vimeo.com/56397162 (See it in HD)

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