[MJKoski]

Irix 15mm looks good on K-1. It goes well with the bulk of the camera body - joy to use with large hands. But the lens has severe issues like skewed near-field focus plane (look like W).

[Erictator]

Irix 15mm looks good on K-1. It goes well with the bulk of the camera body - joy to use with large hands. But the lens has severe issues like skewed near-field focus plane (look like W).

My Irix 15 doesn't do that, and I've shot plenty of flat horizons and architecture to test it. It is not perfect, but doesnt suffer from the moustache effect you describe.

Are you sure you are not thinking of the Samyang 14mm which is well known for the moustache effect? There are plenty of samples of that effect and reviews, and one of the main reasons i went for the Irix. I don't normally like to correct people publicly (and feel free to correct me if you found something I missed), but I'd hate to see people put off on a great little lens like the Irix by mistake.
Eric

[Tan68]

My Irix 15 doesn't do that, ... I'd hate to see people put off on a great little lens like the Irix by mistake.
Eric

I agree
Whether you be more or less right or wrong you are on target to caution people to look to other reviews and infos for the IRIX. Hopefully, anyone reading the MJKloski comment would do so with a grain of salt.

[wizofoz]

Each to his own. Don't trust a review that can't get the test shots in focus.

Precisely...or, in reference to DPR tests, not very precisely

[BigMackCam]

But the lens has severe issues like skewed near-field focus plane (look like W).

As with your views on characteristics and issues with other equipment, I think folks would do well to understand your use of the term "severe" compared to others. I don't doubt you've noticed some W-shaped field curvature, but armed with that knowledge, most people should be able to work with that characteristic...

[MJKoski]

Excuse me, it is as bad as it gets. Just read lenstip review which notes poor performance with near field focusing. Soon it becomes clear why when using the lens...

Here: Irix 15 mm f/2.4 Blackstone review - Image resolution - LensTip.com

"A very significant resolution decrease can be observed on the very border of the frame. It would be difficult to talk about sharp images in that place near the maximum relative aperture; only after employing apertures near f/4.0–5.6 the sharpness level becomes acceptable. The results of the Samyang were a tiny little bit better near the maximum relative aperture but on stopping down the Irix manages to defeat it.

Usually we end our resolution performance review in this place because the results between particular testing charts don’t differ by more than 10-15%. In means that the lens fares similarly at different distances so we can average out all the results and present them in a form of one graph.r

In the case of the Irix, though, the situation is completely different. The lens is clearly designed to work at longer distances; when you position it close to the target it performs much worse. A graph below show differences in resolution for the frame centre between the smallest (close) and the biggest (far away) testing chart."

All it takes is two frames to see the problem - when focused near the edges and borders are far away from image center's plane of focus. When focused to very edges they can be recorded sharp but then center fails immediately.

[BigMackCam]

Excuse me, it is as bad as it gets. Just read lenstip review which notes poor performance with near field focusing.

Oh, I'm familiar with the review. I'm also aware that in real-world use, lenses often perform far better than bench tests would suggest (and sometimes, of course, it's the opposite).

I guess the difference is, you see these as "severe issues" and "problems". I see them as characteristics of a lens, which - when used to its strengths - can produce outstanding images. I've cupboards stacked with lenses of all focal lengths... Some are superb, others average, and still others, unimpressive. Most of them, however, can produce nice images when used to their strengths. Some are more challenging than others in that respect.

As is quite often the case, it's not the basic facts that you and I disagree on, but the extent to which we perceive them as serious or consequential...

[texandrews]

Excuse me, it is as bad as it gets. Just read lenstip review which notes poor performance with near field focusing. Soon it becomes clear why when using the lens...

Here: Irix 15 mm f/2.4 Blackstone review - Image resolution - LensTip.com

"A very significant resolution decrease can be observed on the very border of the frame. It would be difficult to talk about sharp images in that place near the maximum relative aperture; only after employing apertures near f/4.0–5.6 the sharpness level becomes acceptable. The results of the Samyang were a tiny little bit better near the maximum relative aperture but on stopping down the Irix manages to defeat it.

Usually we end our resolution performance review in this place because the results between particular testing charts don’t differ by more than 10-15%. In means that the lens fares similarly at different distances so we can average out all the results and present them in a form of one graph.r

In the case of the Irix, though, the situation is completely different. The lens is clearly designed to work at longer distances; when you position it close to the target it performs much worse. A graph below show differences in resolution for the frame centre between the smallest (close) and the biggest (far away) testing chart."

All it takes is two frames to see the problem - when focused near the edges and borders are far away from image center's plane of focus. When focused to very edges they can be recorded sharp but then center fails immediately.

Yes, well, you left out this part of the review: " I do not hesitate to say that, at working distances typical for this kind of instrument, the lens is able to generate outstanding resolution values."


This is my experience. I don't shoot UWA lenses at close distances, and I doubt any lens designer is thinking that that is how they should be optimized.

[BigMackCam]

Excuse me, it is as bad as it gets. Just read lenstip review which notes poor performance with near field focusing.

Yes, well, you left out this part of the review: " I do not hesitate to say that, at working distances typical for this kind of instrument, the lens is able to generate outstanding resolution values."

It's around this point in such conversations that I like to remember the "Optimist's Creed":

As you ramble on thru life, brother,
Whatever be your goal,
Keep your eye upon the doughnut
And not upon the hole.

[texandrews]

It's around this point in such conversations that I like to remember the "Optimist's Creed":

As you ramble on thru life, brother,
Whatever be your goal,
Keep your eye upon the doughnut
And not upon the hole.

That's good. But I live by my own pessimists' paradigm: A pessimist is never disappointed, but can be pleasantly surprised. But in this case, I surely take your point.

[Kunzite]

A true pessimist cannot possibly be pleasantly surprised. He will manage to find the negative even in the most positive news.

[BigMackCam]

That's good. But I live by my own pessimists' paradigm: A pessimist is never disappointed, but can be pleasantly surprised. But in this case, I surely take your point.

Honestly, I probably inhabit a middle ground... at least where photography gear and consumer goods are concerned. I'm fairly optimistic in my outlook, but very realistic in my expectations, and I tend to look for the good in things. It serves me pretty well

EDIT: Now I think about it, I'm pretty much that way about life in general

[Erictator]

Honestly, I probably inhabit a middle ground... at least where photography gear and consumer goods are concerned. I'm fairly optimistic in my outlook, but very realistic in my expectations, and I tend to look for the good in things. It serves me pretty well

EDIT: Now I think about it, I'm pretty much that way about life in general

I have never been accused of being a "chirpy optimist" but I'm not Marvin the paranoid android either. I try to occupy middle ground, and only let Marvin out for special occasions.

If someone has stuck around through the many years of "When is a Pentax FF coming?!!!" and is still hanging around here, they have to be either an optimist or a masochist!!
Eric

[photoptimist]

Excuse me, it is as bad as it gets. .

Well, I am a photo optimist by name and temperament but I'm realist enough to know that no lens is perfect especially wide open, especially at the extremes of it's range, and especially for lenses at the extremes of focal length.

Honestly, anyone who thinks the Irix minimum focus distance performance is "as bad as it gets" really must be new to photography. There's plenty of lenses out there with worse wide-open sharpness at all focus distances. And if stopping-down fixes the problem, then stop down the damn lens. I don't know of any lenses other than those in the military or professional astronomy that produce diffraction limited sharpness wide open and at all distances.

And, these days, a bit of clever post processing can sharpen a low-ISO image without hideous noise.

[MJKoski]

I meant that field curvature is bad at MFD. No stopping down fixes it, just masks it a bit. Thus, Irix is not a good candidate for super near-to-far focus stacking. Focus plane changes so much from MFD to Infinity.

Pentax 15-30 is better in such case. Or, Nikkor 14-24, Samyang 14mm, Samyang 10/2.8 CS or Zeiss 15mm. Those are UWA lenses I have used for similar purpose.