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Firstly, please be kind I'm no expert and relatively new to tech topics but I do need some guidance.  I've owned an A7rii for two years plus and use CV50 f2 Apo, CV 65 f2 Apo and Batis 135 f2.8 Apo.  All apochromatic because I would like optimum IQ and I'm not prepared to sacrifice swathes of an image in order to remove fringing.  All well and good, then I realise diffraction will rob me of the front to back sharpness I yearn if I don't use the sweet spot of these sweet lenses that appears to be f4-f5.6.  I may be being a little pedantic here but having aquired Xerene and spent many a happy hour learning how to edit a landscape stack shot at the above apertures I begin to lose the will to live.

At 42 mpx the dof problem as I see it is only just beginning and will only become more of a problem on the 61mpx (the current focus of my gas).  Has anyone else wrestled with this or am I avoiding f16 for no good reason.  My other pet hate is lumping a tripod around with me, can anyone offer any tripophobia remedies?  One last thing occurs to me that I don't posses a WA lens, would this be helpful?  I hear rumours of a CV 35 Apo.

Thanks for reading, hope you can help.

Best wishes to one and all.

Edited by Funkiinnit
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  • Funkiinnit changed the title to A7Riv and diffraction limited dof.
  • 2 weeks later...

Diffraction does no rob you of DOF or sharpness.  It robs you of resolution.  No one here has the time to explain all this stuff to you.  I'd suggest a college level class in optics and/or photography -- or spend time at the library reading books by REAL photographers like "Photographic Materials and Processes" by Stroebel, et.al.  (P.S., half of the stuff on "The Web" is WRONG).

Then, once you learn about "circle of confusion" you can make some meaningful decisions.

All lenses suffer from lower resolution when open all the way.  This is where they have the greatest amount of spherical and chromatic aberration.  Stopping down reduces this, but as you stop down diffraction increases.  So you win and you lose.  Even with APO (whatever that means) lenses, you  have to decide what you want and what you  don't want -- DOF, aberrations, resolution, or diffraction.  Most lenses have their best results in the middle -- usually 2-3 stops down.  The only way you can know is to test -- WITH A TRIPOD, of course.

Auto-everything cameras and lenses make some things easier for shutterbugs, but it does not mean they will automatically end up with better results.

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13 hours ago, XKAES said:

Diffraction does no rob you of DOF or sharpness.  It robs you of resolution.  No one here has the time to explain all this stuff to you.

There's no need to be so condescending. I thought along your lines as well when I first read this post, but OP actually has a valid question. He wants maximum depth of field without sacrificing resolution by stopping down too much.

To get maximum sharpness on a high res sensor, most FF lenses need to be used at around F/4-F/5.6, beyond which diffraction degrades image quality. This fairly wide aperture limits DoF, especially on high-res sensors. Based on his post, OP is fully aware of this but the title of the post seems to mix things up a bit.

To OP: unfortunately theres not much to be done about this. In my experience, when you try to stick to the so-called hyperfocal distance, details in the far back still suffer from lack of sharpness. Close down to F/8-F/11 and see if the sharpness is still up to your liking. I'd stay away from F/16.

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Thank you for your considered reply Pieter, chasing iq is beginning to feel a task and a half :)  Might have to find a Sony without an R and a Tamron zoom stuck on it just to see how I like non apo and lack of resolution.  Thanks to XKAES my sense of humour has been tested yet again,  I must look up some real photographers and some real theory just to set me straight.  I suppose I know nothing in today's world :)yet I do remember some things aforementioned from when I started with Kodak B companies in 1968.   Things were different then alas,  3K films per day or night from unloading the vans to reloading them was exciting.  Today it's instant everything including condemnation on the net.  :):):) No matter, thank you again Pieter, thanks to you I'll go practice my stacking and look for a WA to make life easier.

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16 hours ago, thebeardedgroundsman said:

'Scuse my ignorance... are CV lenses made by Voightlander?

I know Batis lenses are made by Zeiss.

I can't help you as I've not had the chance to use such high level kit.

CV represents Cosina Voigtlander who also manufacture a host of Zeiss lenses for Zeiss including the Otus range I believe.  Re "high level kit" : yes good lenses aren't cheap but I spent much more on cheap lenses over a couple of years looking for an inspiring lens until I took the plunge for the CV 65 Apo Lanthar.  It blew all the rest so far away I sold everything else just to pay for it.

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2 hours ago, Pieter said:

 He wants maximum depth of field without sacrificing resolution by stopping down too much.

 

If Pieter is correct, you need to re-read my message.  As you stop down, spherical and chromatic aberration decreases, while DOF and diffraction increase.  You lose some things as you gain some things.  There is no way you can have it all.  The BEST spot for ANY lens -- for film or digital use -- regarding resolution is somewhere in the middle, but maybe the highest resolution is NOT what you need for a particular picture.  Maybe the picture is "better" with more or less DOF, for example, which would mean a little less resolution due to more spherical and chromatic aberration or diffraction.

I'm sure Pieter would agree that this can't all be explained in a few paragraphs on a webpage.

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We all agree with you @XKAES, noone is argueing your sound assessment of the behaviour of optics. OP is just trying to find the optimum in this trade-off for his particular use case, hoping he can do without the tedious process of focus stacking. Since there is no bite size solution to his problem, asking for other peoples opinion on the matter is entirely valid.

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And in my original post, I said the best approach is to test each lens at each f-stop -- with a tripod -- because each lens is different, although they are generally best about 2-3 stops down from open.  Call it "condescending" to advise testing your gear, if you want.  I call it "common sense".  There are lots of dead alpinists who failed to test their gear.

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Thank you gentlemen, if I may attempt to expand on my thinking:  I use Apochromatic lenses because when I remove purple fringing I remove pixels throughout the image therefore negating much of the increase in resolution brought about by changing from 24-42mpx.  These lenses do not perform better as you stop down. they are as good as it gets between wide open and f4.  So, using a good lens at f4 gives fantastic IQ but poor dof hence stacking seems the only option.  Diffraction appears to make a greater impact at lower f stops on more corrected lenses (Apochromatic) and the smaller the pixel size  (higher mpx) the more evident it seems to be.

I understand that everything in photography as in life is a compromise,  I was just curious to see if the thoughts of others can throw any light on an alternative path for me. 

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Thanks for the response.  I'd be interested to hear why you think/believe APO "lenses do not perform better as you stop down."

Keep in mind that lens manufacturers create the lenses that they label as "APO" in several different ways. 

The ones I have are better than non-APO lens when used wide open, but they also improve in resolution when stopped down (until diffraction "takes over") -- just like non-APO lenses.

And where did you get the idea that "diffraction appears to make a greater impact at lower f stops on more corrected lenses (Apochromatic)"?

Can you cite some sort of optical study to back these claims up -- or do you not have a problem with furthering rumors on the Web?

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Fortunately there's objective lens testing websites that do the work for us. The CV 65mm in the center indeed doesn't improve after stopping down 1 stop. The edges improve up to 3 stops when stopping down. The best overall sharpness is achieved at F/5.6, with overall sharpness suffering at F/11 and beyond.

https://www.lenstip.com/517.4-Lens_review-Voigtlander_Apo-Lanthar_65_mm_f_2_Aspherical_1:2_Macro_Image_resolution.html

 

Screenshot_20210305-192125~2.png

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"do you not have a problem with furthering rumors on the Web? "  Firstly we need to straighten this out,  I have no agenda, seek no praise, condemn no one, seek only truth from a perspective of ignorance.  I am guided through the minefield of opinion by what appears to me to make sense, it is my opinion until other information comes my way that replaces/supercedes the current opinion.  It is my learning that most historically taught light theory is repeated dogma of very limited use in light of today's understandings. I am prepared to ditch all I hold as true at a moments notice in light of new information.  I read from many sources on the net,  Lens rentals, Phillip Reeve, Jim Kasson, Diglloyd and many more. I research and try things out almost every day, don't have a TV, don't collect books.  Do listen carefully to lens designers at Leica and CV whenever they give interviews.  i do look for patterns in peoples opinions.   Unfortunately I view peer review as an information control mechanism for those requiring influence with vested interests.

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Thanks for that chart. It shows exactly what I've been saying -- stopping down 2-3 f-stops on most lenses -- even APO -- gives better resolution until diffraction takes over.  This is only one lens -- which shows a decrease in the center after a 1-stop reduction, for sure, but overall it's exactly what I said.  With that lens, the best results would be at f5.6, but other f-stops give good results too -- just avoid f16 & f22 unless you need the DOF for some reason.

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36 minutes ago, Funkiinnit said:

"do you not have a problem with furthering rumors on the Web? "  Firstly we need to straighten this out,  I have no agenda, seek no praise, condemn no one, seek only truth from a perspective of ignorance.  I am guided through the minefield of opinion by what appears to me to make sense, it is my opinion until other information comes my way that replaces/supercedes the current opinion.  It is my learning that most historically taught light theory is repeated dogma of very limited use in light of today's understandings. I am prepared to ditch all I hold as true at a moments notice in light of new information.  I read from many sources on the net,  Lens rentals, Phillip Reeve, Jim Kasson, Diglloyd and many more. I research and try things out almost every day, don't have a TV, don't collect books.  Do listen carefully to lens designers at Leica and CV whenever they give interviews.  i do look for patterns in peoples opinions.   Unfortunately I view peer review as an information control mechanism for those requiring influence with vested interests.

I too try to learn something new every day -- and frequently do.  My unasked for advice?  Don't believe most of what a salesperson tells you. I've learned the hard way.   You've probably heard "Trust, but verify".  In photography it should be "Trust, but test". 

The above chart is a good example.  It's not your lens, but most lenses show very similar results.  Even APO lenses (of whatever type) improve in resolution when stopping down -- until diffraction "takes over".

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If it's pure resolution you're after, I wouldn't go blind on the 'sales term' APO. Usually APO lenses are marketed as top quality lenses (which they often are), but they're not sharpness monsters per se. In fact, the rather cheap Sigma 65mm f/2 DG DN beats the CV 65mm f/2 APO in this regard. Fortunately there's much more to a lens than just sharpness: I'm a CA hater myself and would gladly sacrifice a bit of sharpness to get rid of CA. In your specific case however, I don't expect (Lo)CA to be much of a problem as this is usually only a problem when shooting wide open.

(Image: I took the liberty of comparing LensTips MTF results for both lenses)

CV 65 f2 vs Sigma 65 f2.png

Edited by Pieter
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