Irix 15mm 2.4 with a shift adapter

[decca]

I've been testing the Irix 15mm with my Kipon Nik-FX Shift adapter.

 

This lens is great. very sharp, very low distortion. I have the firefly version, which is made of plastic, and the build quality is very good. One good feature is that it can focus beyond infinity, this is very useful if your adapter is not exactly of the right thickness. There is a click stop at infinity but you can go a little further.

 

One problem is that the lens doesn't have an aperture ring and my Kipon adapter doesn't control the aperture. (There is a Fotodiox shift adapter with aperture control). My solution was to insert a little bit of plastic next to the aperture tab in the lens mount. Now it's locked between f5.6 and f8. This is fine for my application but not ideal for general use.

 

I can shift up to 7mm, at 8mm there is a hard vignette. 

 

 

 

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[milandro]

Very interesting. It would also be nice to see the difference with a software perspective corrected file and one made with the shift of the optics.

 

It would be nice to see what happens with the 12mm Samyang ( which does have an aperture ring).

 

Another consideration that I make by watching this image is that when you have line perfectly perpendicular, they appear to be overcorrected ( it is an optical illusion) and that leaving 1º tilt uncorrected makes them look generally more natural.

 

I don’t know if you are familiar with this but some people talk about it here for example.

 

http://masteringphoto.com/lens-correction-in-photoshop-cca-standard-and-alternative-approach/

 

Note > There is a limit to the amount of correction that can be undertaken in some images before shapes at the edges appear excessively distorted. In some images where the verticals of a building are fully corrected, so that they run parallel to the edges of the frame, there is an optical illusion where the building appears to be growing wider. In these instances Upright may adjust the converging verticals so that they are not absolutely vertical.

[decca]

I've made comparisons with my xf14mm software corrected. The difference is small, you really have to pixel peep. But you lose resolution: with the 14mm, the same scene, from the same distance, perspective corrected has to be cropped and ends up roughly as a 3069 x 4603 px image vs 4000 x 6000 px with the 15mm shifted. (around 23% less linear resolution)

 

As regards to the perfect perpendicular correction I agree completely but this was a test, and I wanted to see the distortion of the lens, I find it's easier to see if aligned perfectly, you can then compare to the edge of the image. The image I posted has no distortion correction.

 

here is the same scene with the 14mm corrected in lightroom:

 

 

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[milandro]

well, I suppose it is a fine balance between loss of resolution because the result is challenged optically ( unlike film, sensors respond very poorly at images formed by slanted light rays) or because it is loss of resolution.

 

On my monitor I cannot tell the difference between the two.

[Aswald]

Nicely done.

[tommaso79]

decca thanks for this test, it is very helpful   now I'm sure I'll buy the IRIX 15mm with shift adapter. I'm using fujinon 10-24 and photoshop for architecture but it is very inconvenience to imagine all the time before take pictures. 

[tommaso79]

Hi Decca!

 

How can you inserted the plastic to the aperture tab? 

Thank you !

Edited October 7, 2017 by tommaso79