Rodenstock Alpagon 40mm HR diffraction limit on IQ4 150

[tashley]

My back is about to arrive and I wonder, given the difference in lens designs between Schneider and Rodenstock, what people consider to be the tightest aperture to shoot at before diffraction kicks in. On the IQ3-100 I'd often shoot at F11 for DOF though people in general had suggested F8 as the furthest one should go unless one wanted a little edge taken off for moire.

Any opinions?

Thanks!
Tim

 

[dougpeterson]

I kind of wish that we had all switched to discussing diffraction "gradients" or diffraction "curves" or diffraction "functions" instead of the diffraction "limit". This is a very important topic and a very important shooting consideration, but "limit" implies there is one number where you fall off a cliff. Instead, whether with 20mp or 150mp, diffraction kicks in over a range of apertures until it is unacceptable for a given kind of use. Where that "limit" for given equipment for a given user therefore depends on the user as much as the equipment.

Comparing the 100mp and 150mp... There are a few factors here: smaller pixels but the pixel design is quite different, the diffraction correction algorithm offsets some of the lowering of the diffraction point, etc. Based on our initial testing we have been advising the following easy rule of thumb:

Whatever you were happy with on the 100mp back... trim off a third of a stop.

So if you were happy at f/11 at 100mp then I'd suggest f/10 for 150mp. I think that's a practical view and falls in line with my personal preferences. If you were someone that was only happy with f/8 on the 100mp then I would suggest f/7 for 150mp.

I'm very eager for the feedback of 150mp users if they find the above rule of thumb matches their experience.

Needless to say this is all based on wanting to take full advantage of the new higher number of pixels in the context of either pixel peeping or large prints. You can shoot the IQ4 150mp at f/22 and it will make a beautiful print – but if you made 4-foot prints at f/22 and f/10 you'd find the f/10 carried far more micro-detail.

 

[dchew]

Hi Tim,
I agree with Doug; the practical shooting f-stop depends on several things (as I'm sure you know!), so "limit" is not really an answer. With the 3100, I would shoot my 60xl at f/13 because the edges would clean up more than the center would degrade. With the 90hr-sw, I would shoot at f/8 if I could get away with it, but the additional diffraction at f/11 was almost unnoticeable unless there was a direct comparison shot. Diffraction Correction in C1 plays a role in that; I think it is quite good.

During my recent test of the IQ4-150, I compared some images using the 90hr-sw. Really splitting hairs at the difference in diffraction, although I'm sure the math shows there to be one. I just believe we are in an area of resolution where everything comes into play on a shot by shot basis. Was there any wind at all? Did you tug on the cable release (even a little)? Did someone within 20 yards stomp their feet? Drive-by booming base? An 0.3 Earthquake?

I think from a lens rendering standpoint, the 40hr is somewhere between the 60xl and the 90hr-sw. My guess is you will see a difference between f/8 and f/11, certainly in the center. But, not if you aren't looking for it... :bugeyes:

Dave

 

[etrump]

Having used the IQ4150 for a couple of weeks now, I think you’ll find that any loss in resolving power of your glass will be offset by improvements in clarity. The difference is quite striking comparing similar output sizes.

You’ll have to adjust your sharpening techniques much the same way we had swiching to the 3100.

 

[tashley]

Thanks to all, very kind and helpful. I’m aware that there’s no ‘cliff’ but there is a area of crumbly land that starts to get more and more dangerous depending on other conditions! I’ll now regard that as being starting at f8 - f10 but will probably still shoot to f11 in order to get DOF unless a really large print is required and conditions allow stacking.

Thanks again!
Tim

 

[tashley]

A brief first test today using the 40HR and shooting a few test shots. The difference in fine detail between f8 and F11 is very clear. The question might be confused by the possibility of some focus shift, though that's not something the lens is known for so I suspect it really is diffraction.

Tomorrow I'll bracket a series from F5.6 thru F11 and make the appropriate comparisons but it looks to me as if milking this sensor for all it is worth is going to involve some very careful technique indeed....

 

[dougpeterson]

A brief first test today using the 40HR and shooting a few test shots. The difference in fine detail between f8 and F11 is very clear. The question might be confused by the possibility of some focus shift, though that's not something the lens is known for so I suspect it really is diffraction.

Tomorrow I'll bracket a series from F5.6 thru F11 and make the appropriate comparisons but it looks to me as if milking this sensor for all it is worth is going to involve some very careful technique indeed....

No meaningful focus shift on this lens between f/8 and f/11. You're seeing the diffraction.

Before you judge the f/11 performance too closely I'd suggest 1) playing with diffraction correction 2) comparing them at your desired print size. On very large prints the difference you see on screen is applicable, but even for A0 prints (~30x40") the difference is much less pronounced.

 

[tashley]

No meaningful focus shift on this lens between f/8 and f/11. You're seeing the diffraction.

Before you judge the f/11 performance too closely I'd suggest 1) playing with diffraction correction 2) comparing them at your desired print size. On very large prints the difference you see on screen is applicable, but even for A0 prints (~30x40") the difference is much less pronounced.

My last sold gallery print was 1640 x 1230mm which works out, for the 150mp back, at almost exactly MacBook Pro retina resolution. And I can see it plain as day on that screen... so now to find my cutoff point. I hate third stops - they make shutter speed calculations a mindfck!

 

[tashley]

So today I did some tests and have determined that a fussy eye will see the difference between F11 and F8 at resolutions of approx 220DPI and coarser, and that a very fussy eye will see the difference between F10 and F8 but that F9 and F8 seem very hard to distinguish. Also, frankly, a touch extra sharpening, contrast and clarity (really just a touch) can make the F11 so close to F8 that I think it's worth it for the extra DOF where required. Real best practice would be to tilt or focus bracket, but I'm just gonna go with the maxim of F11 where needed and deal with it in post.

 

[dougpeterson]

So today I did some tests and have determined that a fussy eye will see the difference between F11 and F8 at resolutions of approx 220DPI and coarser, and that a very fussy eye will see the difference between F10 and F8 but that F9 and F8 seem very hard to distinguish. Also, frankly, a touch extra sharpening, contrast and clarity (really just a touch) can make the F11 so close to F8 that I think it's worth it for the extra DOF where required. Real best practice would be to tilt or focus bracket, but I'm just gonna go with the maxim of F11 where needed and deal with it in post.

This comports with our experience.

In short: use f/8 when you don't need more DOF, use f/11 without hesitation or regret when you do.

 

[eisbaer]

I noticed the same behavior.

F8 is sharper then F11. Using F9 is great, and using F11 is not as sharp as F8, but as you have 150MP versus 100MP... you still have a lot more resolving power at F11 with the IQ4 then with the IQ1/3 100.. Even if its not ideal for the IQ4 150...
It's always the same game. A Nikon D3 with 12 MP... Diffraction kicks in at F13, Nikon D850, diffraction kicks in at F7.1. But even if diffraction kicks in with the D850 at 7.1, with F13 the D850 resolves 2-3 times of what the D700 did.

Same goes with the IQ4 150... Diffraction kicked in with the IQ3 100 at F9 to F10... with the IQ4 150 at F7.1 to F9... but the IQ4 resolves much better then the IQ3...

So have fun.. If you need max quality and you do not worry about DOF, go with F 7.1 to 9 with the IQ4 150. If you need more DOF, go with 11 to 13 as you still have more resolving power as with the IQ3 100.
I am so eager to see what they really will do with the IQ4 150 in terms of ETTR and ISO Invariance. Came back from a shoot two weeks ago and had about 16F-Stops of Dynamic Range... at the Zugspitze, early morning, just cool... Never seen this before... But when do you release a cable and a capture solution for Alpa or Tech Cameras...
Great job you did for the back, I am really blown away, but how about let us have to use your stuff to the fullest? Since 6 weeks I am sure the handbrake on my IQ4 150 is always on... at least with my Alpa...

Frank

This comports with our experience.

In short: use f/8 when you don't need more DOF, use f/11 without hesitation or regret when you do.

 

[narikin]

... But when do you release a cable and a capture solution for Alpa or Tech Cameras...
Great job you did for the back, I am really blown away, but how about let us have to use your stuff to the fullest? Since 6 weeks I am sure the handbrake on my IQ4 150 is always on... at least with my Alpa...

Alpa announced it today. Small pre-production numbers, but they are shipping. check their website & contact your dealer.

Phase just need to speed up the wake-up sync of IQ4 - its 8 times longer than IQ3 according to Alpa!

 

[eisbaer]

Alpa announced it today. Small pre-production numbers, but they are shipping. check their website & contact your dealer.

Phase just need to speed up the wake-up sync of IQ4 - its 8 times longer than IQ3 according to Alpa!

#Was at the phone today with Alpa as we are dealers for Alpa... Sadly no solution for Alpa Copal Lenses...Solutions are there for silex shutters.. in small quantities. but not for copal lenses. Still waiting for Phase here ... Not only for wake up, but for having a solution at all..