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10-16-2021, 09:13 AM   #16
dms
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I have used the Cokin universal ring (P series) to mount filters on my FE lenses. (Not the 10-17mm.) The ring fits lens with outer diameter up to 78mm. It has 3 set screws that friction fit onto the lens barrel (the outside). Not very robust, so not something you carry attached. As mentioned you will see the ring at very wide FLs.

10-16-2021, 11:00 AM - 1 Like   #17
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QuoteOriginally posted by BigMackCam Quote
Out of curiosity, once you've de-fished an image, what pixel dimensions do you end up with - or does it stay the same?
That is a good question. It has been a long time since I've done one and I don't remember. I use PTLens.

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10-16-2021, 01:25 PM - 1 Like   #18
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IIRC, image size in PTLens stays the same, unless you crop smaller to remove the black bulges that appear when you de-fish.

And just to throw some chaos into the original discussion, the ridges on the inner surfaces of the DA 10-17's built-in hood are exactly the right size/spacing to grip 58mm filter threads. Vignetting will be a problem.
10-16-2021, 07:29 PM   #19
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I am a little confused by the "de-fishing" comments; if one is going to "de-fish" in post, then why use a fish-eye lens to begin with ?

As you say- back to filters; as said by others- the CP and ND are problematic, but a graduated filter- just needs to be "large"- I guess!

10-16-2021, 10:38 PM   #20
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QuoteOriginally posted by DonV Quote
A graduated filter- just needs to be "large"- I guess!
Actually, even an infinitely large flat filter will still vignette at 10mm
180º is very unforgiving
10-17-2021, 01:09 AM - 1 Like   #21
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QuoteOriginally posted by DonV Quote
I am a little confused by the "de-fishing" comments; if one is going to "de-fish" in post, then why use a fish-eye lens to begin with ?

As you say- back to filters; as said by others- the CP and ND are problematic, but a graduated filter- just needs to be "large"- I guess!
A wide rectilinear lens will have an apparent distortion at the edges, as the same angle moves thru a wider distance, and thus circles for example become oval shaped. A FE after a distortion adjustment, can actually remove this distortion (anyway Fish eye hemi is designed to do this), and thus look much more natural. And a FE after such adjustment still is likely to have a wider field of view (as the FE center horizontal is not narrowed at all, just the "wings").

I basically always use a FE rather than an extreme wide angle, although I find a FF FE on an APS-C crop sensor (and Fisheye Hemi) gives me the best results. In fact my Pentax 17mm f/2.8 wide open does quite well (on my K-5's).

I actually like them so much I have three FE lenses in Pentax K, one in Nikon F, and one Pentax Q--and the FE look is something I almost never go for.
10-17-2021, 06:10 AM   #22
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A defished fisheye image often is still much wider than a rectilinear image from a similar focal length. Sometimes this works very well, other times it can exaggerate features in the image.

10-17-2021, 09:54 AM   #23
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Thanks guys,
I just re-read the PF story on the 4 wide angle lenses- and it makes my head hurt!

I believe I have an innate prejudice against FE lenses- as I prefer my lines to be "straight"; though occasionally a FE perspective/projection does work well.

As to filters, that "large" filter must be "curved" too- or maybe hemispherical.
10-17-2021, 11:22 AM   #24
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QuoteOriginally posted by DonV Quote
Thanks guys,
I just re-read the PF story on the 4 wide angle lenses- and it makes my head hurt!

I believe I have an innate prejudice against FE lenses- as I prefer my lines to be "straight"; though occasionally a FE perspective/projection does work well.

As to filters, that "large" filter must be "curved" too- or maybe hemispherical.
I have attached an image taken with the K-5 and 17mm f/2.8 FE at f/4 defished w/ fisheye hemi. (This is a record of the scenery for a theater production.)

The fisheye hemi defishes basically in one direction to make people look right and hardly lose any of the image, you can see the edge of the stage is a curved line, so it is not truly rectilinear, and of course this image is all about straight lines so a tough test.
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10-17-2021, 12:02 PM   #25
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dms,
thanks for the picture- great illustration defishing; and good example of why I like the "rectilinear" lenses.

I don't do post processing, except for minimal crop/adjust; thus the use of a non FE lens for me.

Could you have taken nearly the same view with a 10 or 14 mm rectilinear lens?
10-17-2021, 01:52 PM - 1 Like   #26
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QuoteOriginally posted by DonV Quote
Could you have taken nearly the same view with a 10 or 14 mm rectilinear lens?
Not even close. The DA10-17 @ 10mm de-fished is still slightly wider than the Sigma 8-16 @ 8mm....

Sigma 8-16 @ 8mm (complete with native barrel distortion and flare)



10-17 @ 10mm de-fished (note the loss of resolution at the edges)



....and to show how much image you lose with distortion correction (and how much sharper the edges are) here it is uncorrected.

10-17-2021, 02:24 PM   #27
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QuoteOriginally posted by gofour3 Quote
Pentax used to have better options for filters for fish-eye or extreme wide angle lenses, like built-in rear-mount gel filter holders or built-in filter dials with a choice of three or four filters. Unfortunately those days are gone.

You'd have to pickup an old manual focus K or A Series lens to get these filter options.

Phil.
The Irix 15 does have a rear gel filter holder. It also accepts 95mm filters on the front.
10-17-2021, 02:27 PM - 1 Like   #28
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Sandy, your example is one reason I like fisheye hemi. I used hemi-2 plus extending the image 10% in Y axis--a quick guess to make the perspective correction better. (Presume you don't mind my using your image.)

The disadvantage of fisheye hemi (as seen here) is it does not make a true rectilinear image--some edges are still curved--for me I like what it does.
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10-17-2021, 02:30 PM   #29
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QuoteOriginally posted by dms Quote
Sandy, your example is one reason I like fisheye hemi. I used hemi-2 plus extending the image 10% in Y axis--a quick guess to make the perspective correction better. (Presume you don't mind my using your image.)
Not at all. That's quite impressive!
10-17-2021, 03:44 PM   #30
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QuoteOriginally posted by sarge Quote
I would like to pick up the 10-17mm Fisheye lens for my ultra wide option. I want to be able to use a filter holder on it for landscape shots though. Is there an adapter made for this?
I ran across these clip filters in another thread a while back. I've no experience with them, but they might be a possibility depending on what you want to do and the design of the lens. They have ND, IR, UV, and astro filters. They are expensive. There are other manufacturers of clip filters with different designs as well.
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