Samyang / Rockinon 7.5 mm feedback + questions

I love my "Rokfish". I can't say I'm particularly expert with the lens, but a few things I've learned:

- If you keep the horizon dead in the centre, then on landscapes, you can often get a fairly regular-looking photo without defishing.

- Hugin does a good job of correcting bent horizons (when you don't put it on the centre-line) without defishing it. I forget exactly now how to do it, but it's a question of dragging the image in one of the preview screens.

- Focus ring calibration tends to vary from copy to copy. It's worth experimenting with yours to find exactly where the hyperfocal distance is for f5.6 and f8. Then mark the barrel with that setting and in future, there's no need for focusing when the light's good and you're not focussing close up.

- If you're a Lightroom user, there's a nice plugin called LensTagger that runs Exiftool as a batch job on selected photos. It's a quick way to tag all your images with the correct lens (but no aperture setting of course).

- If you see a rainbow, grab your Rokfish - you can get the entire arc in a single shot. Cool!

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Fishie Rainbow by Paul Kaye, on Flickr


Hope this helps!

 

My main comments would be to make sure that your fingers, feet, shadow and dogs are out of the photo. I have had way too many photos with these problems.

 

Someone in this forum posted defished lens profiles for LR a while back. You can do a search.

 

If you are using LR be sure to have it correct for chromatic aberration - this improves the corners quite a bit. You can see CA around the leaves in Paul's image even at web size, it is pretty significant CA but corrects automatically very nicely in LR. (BTW, very nice rainbow shot Paul!).

Ken

 

If you are using an Oly camera, don't forget to set the IS focal length manually (from the SCP, highlight the IS box and press the middle button, then INFO).

If you decide to use Hugin to defish, set the focal length to 7.66, not 7.5, you get more accurate results.

If you want to keep the image 'fishy', reproject to Stereographic. Still clearly fishy but somehow looks less odd.

Sort out CA and apply any noise reduction *before* reprojecting.


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It's a great lens...I usually focus it to just shy of infinity and forget about it. Every now and again I have to tweak it a bit, but for landscapes, etc, it works perfectly, regardless of the aperture.

 

I like to set it at 16:9 for "panorama mode"  

 

As a senior I love the "Rokfish" nickname! The're probably not a lot here who remember Issac Hayes on "The Rockford Files".
Bobby

 

As with any fisheye, horizon placement is key in determining how "fishy" the image is going to look. Put the horizon in the center of the frame if you want less distortion:

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Put it at the edge if you want more:

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And if you're into panos, consider getting a tripod, a Nodal Ninja, and learning to stitch 360x180s.

 

Rokinon 7.5 won't focus - options to fix this?

I bought a used Rokinon 7.5 fisheye lens, and suspect I have a bad copy. My problem is that images are extremely soft, while many reviews claim this to be a fairly sharp lens. I have tried all apertures with my GH4 and GH3 cameras, but the lens won't focus closer than 5 or 6 feet. Even at that distance, images are very soft. I have read posts about the infinity focus being uncalibrated with this lens, and that some brave souls have modified their lenses somehow. Is there a way to fine tune the lens myself, or do I need to send it back for repair?

 

Check the back side of the lens (the bayonet side). I have seen a few reports where the back element had been loose. Simply turn the metal ring to lock that last element again, if its loose.
The focus is not automatic of course, but most people get excellent results with the lens just short of infinity and f5.6 or 8. For closer work, make sure not to focus too closely, the lens can be turned to focus very close up.

 

The back element might be loose. Just screw it carefully clockwise so that it is tight. But try not to touch the glass surfaces.

 

Check the rear lens element - it comes loose on some copies of the fisheye, and can simply be screwed back into the lens body.

I supposed its also possible a lens element has been knocked out of place from a drop, but I would check the rear element first.

 

Thanks for all the replies. I removed the metal mount and checked the rear lens element, which appears to be snug.

 

Mine is tight as a drum. Make sure if you mount the lens on a body with IBIS that you set the focal length to 8mm. They don't have a 7.5mm focal length but the IBIS will ruin your shots if it's turned on and you haven't set the lens focal length to 8mm.