[TerryL]

Hello,
I have an Irix 15mm, and need some help. My infinity indicator where you feel the slight stop is right on the spot. Although, the focus ring will continue past it. That's the issue where Irix gives you instructions to calibrate it yourself. Has anyone ever attempted to do this calibration? Can I leave it as is as long as I don't go past the indicator spot? Does this issue affect the lens even though I stop at the indicator? I'm struggling to get fine focus, and trying to rule out issues with the lens, and my methods of focusing. Your help is appreciated.
Terry

[pentageek]

That's the issue where Irix gives you instructions to calibrate it yourself

Actually the manual describes the calibration when infinity focus is not spot-on, what has nothing to do with the situation you described. Many lenses go past infinity mark, in fact it is pretty common. My Irix also exhibits this behaviour, but it does not affect image quality in any way.

[Jens Lyn IV]

This is normal. The focus ring turns past infinity to accommodate infrared photography - the small 'R' on the DOF scale indicates focus in the infrared spectrum.

[TerryL]

Actually the manual describes the calibration when infinity focus is not spot-on, what has nothing to do with the situation you described. Many lenses go past infinity mark, in fact it is pretty common. My Irix also exhibits this behaviour, but it does not affect image quality in any way.

Thank you. Actually, that's good to know. Mine must be normal, then. I must just need to learn to focus it. Colors are great, I'm just not getting sharp images.
Terry

---------- Post added 06-09-18 at 10:22 AM ----------

This is normal. The focus ring turns past infinity to accommodate infrared photography - the small 'R' on the DOF scale indicates focus in the infrared spectrum.

Thank you, Sir. I guess I have to learn. I'll just keep working with it. Beautiful lens.
Terry

[LensBeginner]

Actually the manual describes the calibration when infinity focus is not spot-on, what has nothing to do with the situation you described. Many lenses go past infinity mark, in fact it is pretty common. My Irix also exhibits this behaviour, but it does not affect image quality in any way.

Not only it's common, it's also desirable, since if the lens gets too heated up the barrel can expand and this can result in the inability to attain infinity focus.
Not deal-breaking on a UWA, but on a tele...

[pentageek]

Colors are great, I'm just not getting sharp images.

Focusing of UWA lens can be tricky - try to use hyperfocal setting under good lighting conditions to verify whether it is a problem with the lens, or rather technique.

[TerryL]

Focusing of UWA lens can be tricky - try to use hyperfocal setting under good lighting conditions to verify whether it is a problem with the lens, or rather technique.

That's exactly what I'm going to do, tomorrow. I've been shooting at f/11, and can't find a sharp part of the image. Frustrating. I bought it from Irix USA. Their website says that if you experience a problem, that there are people there to help you. Good luck! I can't even get a reply. Not even all week, and about 5 times.
Terry

---------- Post added 06-09-18 at 02:42 PM ----------

Not only it's common, it's also desirable, since if the lens gets too heated up the barrel can expand and this can result in the inability to attain infinity focus.
Not deal-breaking on a UWA, but on a tele...

LensBeginner,
I looked at your images. You are certainly talented!
Terry

---

Last edited by TerryL; 06-09-2018 at 02:00 PM. Reason: spelling

[LensBeginner]

LensBeginner,
I looked at your images. You are certainly talented!
Terry

Hahaha no I'm not!
Since I took up photography I worked on my technique, and got it down ok-ish... but I still lack imagination and that playful craziness that makes up great pictures. Gotta work on that. Plus, my gallery on this forum is kinda old-ish apart from a couple of recent additions, and never got around to make a proper Flickr profile... just using it as utility hosting.
Thanks anyway for your generous compliment

[TerryL]

Actually the manual describes the calibration when infinity focus is not spot-on, what has nothing to do with the situation you described. Many lenses go past infinity mark, in fact it is pretty common. My Irix also exhibits this behaviour, but it does not affect image quality in any way.

Pentageek,
I am new to this type of focusing with manual focus lenses, especially using the hyperfocal scale. Can you recommend give me an easy method to shoot, on tripod, to test for sharpness? I want to verify that my lens is a keeper, and will work on using it later. I really hope it is, and look forward to using it, and using filters.
Thank you very much.
Terry

[LensBeginner]

I have tested my Sigma 10-20mm this way:
Take a close target, an infinity target and another one roughly in the middle of the scale. It's best if they are flat: for instance you could use the usual brick wall for the near focus test.

Set the lens wide open, camera on a tripod, with the sensor exactly parallel to the target.

Focus by hand in magnified Live View in the centre of the frame.
Check each side and each corner of each picture: if they are sharp on one side but soft on the other, you could have a problem.

If you don't like what you see, check again but this time stopping the lens down progressively.
If you still get a soft side by f/8, the lens is probably decentered, otherwise you're fine.

[TerryL]

I have tested my Sigma 10-20mm this way:
Take a close target, an infinity target and another one roughly in the middle of the scale. It's best if they are flat: for instance you could use the usual brick wall for the near focus test.

Set the lens wide open, camera on a tripod, with the sensor exactly parallel to the target.

Focus by hand in magnified Live View in the centre of the frame.
Check each side and each corner of each picture: if they are sharp on one side but soft on the other, you could have a problem.

If you don't like what you see, check again but this time stopping the lens down progressively.
If you still get a soft side by f/8, the lens is probably decentered, otherwise you're fine.

Ok, I will try that. Today, I tested this way: my tractor was out in front of my sidewalk, then my deck, then my house. I wanted everything from the tractor to infinity to be in focus. I focused slightly in front of the tractor, reframed, shot on a tripod, at f/11 and f/16. I fully expected for the tractor, deck, and house to be in focus. It looked terrible. Is your Sigma for a cropped sensor?
Thank you for your help,
Terry

[LensBeginner]

Ok, I will try that. Today, I tested this way: my tractor was out in front of my sidewalk, then my deck, then my house. I wanted everything from the tractor to infinity to be in focus. I focused slightly in front of the tractor, reframed, shot on a tripod, at f/11 and f/16. I fully expected for the tractor, deck, and house to be in focus. It looked terrible. Is your Sigma for a cropped sensor?
Thank you for your help,
Terry

Yes it is:
Sigma 10-20mm F3.5 EX DC HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database

[pentageek]

There is special 'hyperfocal' scale on the barrel of your Irix. Align its '11' mark with focus mark - infinity mark should align with '11' mark on depth of field scale. On the other end of scale you will see that '11' indicates 1.5m / 5 ft. It means that everything between 1.5 m and infinity will be in focus as long as f-number is 11 or higher. Now lock the focus using the ring in front the lens, and go out to take photos. The scene you described seems to be good candidate - as long as you use f/11 and do not get too close (remember, 1.5 m), everything should be in focus. Post the results, please, so we can take a look and see if they are really terrible. If you are interested in more detailed description of the hyperfocal distance, there is a lot of material available online, including calculators and mobile apps. There is one caveat: results provided by calculators may vary, as they depend on input parameters - for instance, I use Hyperfocal Pro app, and for given f-number it shows greater depth of field than the scale on Irix barrel.

[TerryL]

There is special 'hyperfocal' scale on the barrel of your Irix. Align its '11' mark with focus mark - infinity mark should align with '11' mark on depth of field scale. On the other end of scale you will see that '11' indicates 1.5m / 5 ft. It means that everything between 1.5 m and infinity will be in focus as long as f-number is 11 or higher. Now lock the focus using the ring in front the lens, and go out to take photos. The scene you described seems to be good candidate - as long as you use f/11 and do not get too close (remember, 1.5 m), everything should be in focus. Post the results, please, so we can take a look and see if they are really terrible. If you are interested in more detailed description of the hyperfocal distance, there is a lot of material available online, including calculators and mobile apps. There is one caveat: results provided by calculators may vary, as they depend on input parameters - for instance, I use Hyperfocal Pro app, and for given f-number it shows greater depth of field than the scale on Irix barrel.

Thank you so much. This will be very helpful.
Terry

[TerryL]

There is special 'hyperfocal' scale on the barrel of your Irix. Align its '11' mark with focus mark - infinity mark should align with '11' mark on depth of field scale. On the other end of scale you will see that '11' indicates 1.5m / 5 ft. It means that everything between 1.5 m and infinity will be in focus as long as f-number is 11 or higher. Now lock the focus using the ring in front the lens, and go out to take photos. The scene you described seems to be good candidate - as long as you use f/11 and do not get too close (remember, 1.5 m), everything should be in focus. Post the results, please, so we can take a look and see if they are really terrible. If you are interested in more detailed description of the hyperfocal distance, there is a lot of material available online, including calculators and mobile apps. There is one caveat: results provided by calculators may vary, as they depend on input parameters - for instance, I use Hyperfocal Pro app, and for given f-number it shows greater depth of field than the scale on Irix barrel.

I have the shot using the hyperlocal scale, but I can't figure out how to download here. Shucks.
Terry