Let's talk about lenses.

[Ben Rubinstein]

Got my little Pentax M 24mm f2.8. Lovely little lens, only done some very perfunctory testing but sharpness is not bad wide open, OOF areas are smooth and Pentax like. I haven't had a chance to test it stopped down but I have little doubt that it will be very nice. I also have the feeling that the corners will be impressive from how they look wide open. I'll update though and hopefully add pics. Selling the OM 21mm and the new OM-NEX Novoflex adaptor if anyone is interested.

 

[Ben Rubinstein]

Here we go. My first image with the new lens.

A7r, Pentax M 24mm f2.8 lens at f11 (I think). Far corners are better than the the mid corners which is just weird. It's not a lens for when you want everything resolved perfectly but it's sharp in the centre and a lot of fun. I can provide a link to the raw file if anyone is interested.

 

[Michael Nagel]

Hi Ben,

looks good - hope that the lens will continue to please.
For the sharpness - maybe the Petzval field curvature is not that flat and complex.

Best regards,
Michael

 

[Ben Rubinstein]

Thanks for that suggestion Michael. Would you mind looking at the raw file if I post a link?

 

[Ben Rubinstein]

The picture which has probably had me put on the Homeland Security List as a suspected terrorist. How was I to know that it was the back of the US Consulate? I was messing around in the back streets near King David Street in Jerusalem when I was suddenly surrounded by security people. They were very polite and courteous but called over police to make sure I allowed them to photograph my ID card. As I said, they were really polite, I just hope the computer systems they feed with my data are as friendly. A7r (the head security guard recognised it as a mirrorless camera which left me impressed!) with Super Tak 50mm @ f1.4

 

[Michael Nagel]

Thanks for that suggestion Michael. Would you mind looking at the raw file if I post a link?

Hi Ben,

if you don't expect a speedy answer and if you mind converting it to DNG - yes. I do not have a RAW converter that works for A7r files...

Best regards,
Michael

 

[Ben Rubinstein]

Here is the RAW file, got a bunch of edits done to it but feel free to play. You can see what I mean about the corners at the bottom on either side. The trees are soft but the grass is sharp.

 

[Michael Nagel]

Hi Ben,

I downloaded it and rawtherapee can open it. More later this week (sorry).

Best regards,
Michael

 

[Ben Rubinstein]

Thanks Michael. I just can't work out what I'm seeing. The lens seems to jump from about 2 meters to infinity (hard stop) almost immediately. That image was shot at infinity, f16. The tree trunk is sharp, the building behind it is sharp, the leaves seem sharp. Problem is that anything further away on either side is not sharp. Almost as if infinity is correct for the centre only but the edges and corners are closer to 2-5 meter focus length when at the infinity stop. That make sense at all? Using a Novoflex adaptor which is unlikely to be the problem.

 

[Jerome Marot]

I had a look at the dng. Probably, the lens has some field curvature. At the centre, focus is on the benches, so everything between the tree and the far field appears sharp. At the corners, focus is much closer, so the grass is sharp but the far trees aren't.

 

[Michael Nagel]

Hi Ben,

I am still trying to figure out, so here is just one observation of mine:
It seems to me that the bunch of trees to the left look less sharp to me than the bunch on the right side.

Best regards,
Michael

 

[Ben Rubinstein]

Been talking to Stefan Steib from Hartblei, apparently it's very noticeable astigmatism. He suggested filing down the adaptor to allow the lens to focus past its infinity stop to allow me to choose a mid point between the centre and corner infinities.

 

[Michael Nagel]

Hi Ben,

Did not expect this, but I am not an expert here. Not that good...

This review shows not so stellar results as well (and I am being kind).

Best regards,
Michael

 

[Ben Rubinstein]

Hey Michael, the lens cost me 100 Pounds, I bought it just for some fun which it is, not worrying about the problems so much. When I go for a real wide angle solution for commercial work I'm hoping to get the Zeiss 18mm in E mount when they finally get round to releasing it. Either that or wait for the sony 16-35mm f4 lens for E mount that is rumoured and hope it's good.

 

[Michael Nagel]

Hi Ben,

Still - I hoped for better. the Tokina seems quite OK (on APS-C).
Hope you continue to have fun with it nevertheless...

Best regards,
Michael

 

[Jerome Marot]

Been talking to Stefan Steib from Hartblei, apparently it's very noticeable astigmatism. He suggested filing down the adaptor to allow the lens to focus past its infinity stop to allow me to choose a mid point between the centre and corner infinities.

This is so wrong I don't know where to start. Let me see:

-astigmatism is something else
-you don't "file" an adaptor
-you don't want to "focus ad mid point between center and corner".

 

[Ben Rubinstein]

He actually suggested filing down the mount of the lens. When I was nervous about it he suggested filing down a cheap adaptor, in any case the idea is to allow focusing past infinity where the problem is occurring.

What is your explanation and how would you work around the problem Jerome? At infinity the corners are focused some 20-30 meters behind the centre.

 

[Jerome Marot]

He actually suggested filing down the mount of the lens. When I was nervous about it he suggested filing down a cheap adaptor, in any case the idea is to allow focusing past infinity where the problem is occurring.

What is your explanation and how would you work around the problem Jerome? At infinity the corners are focused some 20-30 meters behind the centre.

You probably mean "when the center of the lens is focussed to infinity, the corners have objects at 20-30 meters distance in focus". What you wrote is that the corners would be focussed 20-30m further away than infinity, which does not make sense.

The advice "file the mount" means that you would make the mount a bit shorter (I'll explain how shortening the mount register is done further below and it does not imply using a file at all). If the mount is made shorter, say enough so that the center and the corner misfocus are equal and opposite, then a ring zone midway between the center and the corner will be in focus. This is rarely desirable, but you can do that if you wish.

If you like to try to shorten the mount register, doing so is usually easy and not destructive. Unscrew the mount of your lens (make sure you have the right Phillips screwdriver, it is either 0 or 00, possibly 000 for the electronics contacts if your lens has them, and using the wrong driver will damage the screws). Under the lens mount, you will normally find shims. Mark their position (all of them) and take off one of them (if they are rings going under the whole mount) or one under each screw (if they are small rings piled under each screw). You'll need a felt pen which can write on metal to mark the positions.

If there are no shims in your lens, try the adapter (but in my experience, these Chinese adapters rarely have shims). If there are no shims anywhere, you'll need a machinist who has experience with fine mechanics. The mount of the lens (or adapter) normally rests on 3 rectified surfaces. They can be made shorter, but they need to be the same distance. Do you own a micrometer-screw caliper?

 

[Ben Rubinstein]

What I mean is that when the centre of the lens is correctly at infinity, at the infinity mark of the lens, the corners of the lens are focused about 2-3 meters away instead of at infinity.

 

[Jerome Marot]

What I mean is that when the centre of the lens is correctly at infinity, at the infinity mark of the lens, the corners of the lens are focused about 2-3 meters away instead of at infinity.

Then, for a 28mm lens, if you want to correct that error (3m to infinity), using Descartes formula, you will need to shorten your mount about 0.15mm. Can you measure that to an accuracy better than 0.01mm around your mount?

 

[Ben Rubinstein]

It's a 24mm lens. Stefan had suggested grinding off 0.1mm from the inside of the mount after removing it. I don't have the tools or knowledge however for a task like this.

 

[Doug Kerr]

Hi, Jerome,

Then, for a 28mm lens, if you want to correct that error (3m to infinity), using Descartes formula, you will need to shorten your mount about 0.15mm.

Perhaps about 0.26 mm (assuming initial focus at 3 m).

Best regards,

Doug

 

[Jerome Marot]

Perhaps about 0.26 mm (assuming initial focus at 3 m).

That is what Descartes formula gives, but one needs to correct half the error, so that the center and corners are equally mis-focussed.

 

[Doug Kerr]

Hi, Jerome,

That is what Descartes formula gives, but one needs to correct half the error, so that the center and corners are equally mis-focussed.

Oh, of course.

Thanks.

Best regards,

Doug

 

[Ben Rubinstein]

My daughters birthday tomorrow, my wife bought her a balloon to keep her going.

A7r, 50mm Tak Super. I shot this at f1.8 rather than my usual f1.4. Shooting into the light with an already soft and dreamy aperture would not have worked when the subject is in the shadow, it would have flared too much to see details. I find f1.8 a very good 'working' rather than 'special use' aperture on this lens. Like with my Canon 50mm 1.4, wide open is dreamy and you can do wonderful things if you know how to use it but once you get to f1.8 it's sharp and contrasty. The Pentax less than the canon of course but f1.8 is a very workeable aperture. Amazing the difference that 1/3 of a stop makes on these fast 50mm's. My 50L was the same. f1.2 was special and unique, stop it down to f1.4 and it becomes a jack of all trades working aperture.

 

[Ben Rubinstein]

A7r 50mm Tak Super @f5.6. Vignetting in post, this lens from f4 can equal most modern normal lenses for clarity and sharpness.

First decent rain this year started yesterday here in Jerusalem. This is from the balcony outside one of our studios. I got caught up in a heavier downpour than this yesterday while biking home, biking 4.5 miles in half a foot of rushing water, visibility zero, eyes blinded by driving rain, expecting the electric motor of my bike to cut out at any second, honestly, don't think I've had so much fun in years! Rain here in Jerusalem or indeed the entire country is a blessing and a joy. Wonderful way to feel about rain having grown up in Manchester, UK where rain is a constant non stop dreary reminder of the fact that we don't live anywhere more exotic.

Starting to really like the Tri-X preset in Nik Silver Efex Pro 2. It's a gorgeous film and look. It's not the same with digital but it's a nice place to start from.

 

[Asher Kelman]

My daughters birthday tomorrow, my wife bought her a balloon to keep her going.

A7r, 50mm Tak Super. I shot this at f1.8 rather than my usual f1.4. Shooting into the light with an already soft and dreamy aperture would not have worked when the subject is in the shadow, it would have flared too much to see details. I find f1.8 a very good 'working' rather than 'special use' aperture on this lens. Like with my Canon 50mm 1.4, wide open is dreamy and you can do wonderful things if you know how to use it but once you get to f1.8 it's sharp and contrasty. The Pentax less than the canon of course but f1.8 is a very workeable aperture. Amazing the difference that 1/3 of a stop makes on these fast 50mm's. My 50L was the same. f1.2 was special and unique, stop it down to f1.4 and it becomes a jack of all trades working aperture.

Well, Ben,

This is so impressive! Reminds me of the look of the best large format lenses like the Cooke PS945. Shooting into the light at that aperture sends angels from the periphery with wands to paint an extra, but so delicate spray of glowing light at the highlights all over the field. I will do a side by side comparison with film one day.

Asher

 

[Ben Rubinstein]

Thanks Asher. Stopped down rather more than that for this shot...

A7r, Pentax 50mm Tak Super @ f8

Biking home in the freezing cold there was a very ominous cloud overhead, I could have raced it and almost made it when I saw this scene over the Ein Kerem valley. I was just one minute from home but I couldn't leave light like that. I stopped and got my camera out as the hailstones started, hard and fast. Got the shot and biked home. Riding into a hailstorm is really painful! Worth it for the shot though. A rare colour shot for me and a nice return to the 6X12 ratio I love so much. The detail from this lens and camera combination is unbelievable. I just can't believe how much is being resolved!

 

[Ben Rubinstein]

While on a colour theme, here's one from a 'sleeper' lens, the Pentax Takumar Super 35mm f2, shot here at f11 on the A7r.

Complex shoot, 6 lights, fog machine, sound trigger, etc. Rather pushing the envelope of this wedding photographers skills but fun. Had to be careful with light placement as it's a single coat lens and I had a lot of light happening in the shot.

 

[jake klein]

I've been really enjoying this Nikkor 28mm f2.8 ais. I'm not sure if it's the fact that I didn't shoot with a FOV wider than a 50mm for almsot 5 years or not but I'm enjoying it quite a bit.