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Thread: DAC corrections

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    DAC corrections

    For those interested in Hasselblad's aproach to lens design and in particular how DAC corrections work - you will find a very interesting and thought provoking article in the latest issue of Victor. This is an online publication.

    A number of thought provoking issues emerge- in particular the fact that high resolution digital capture makes it more diffcult for lens design to deliver super sharp images at any distance.

    Interestingly - Hasselblad point out the difference betwen C lenses and H lenses in terms of strengths and weaknesses for both.

    http://www.victorbyhasselblad.com/en...ne-/22008.aspx

    Recommended for people who prefer not to satisfy themeselves with repeating other people's BS. It seems that Mamiya is embarking on a similar philosophy with their new D spec lenses and coming corrections in Capture One.

    I would be very skeptical of third party software that does not have access to the lens maker's prottype optic algorythms in applying DAC corrections and yet claims to be able to apply same.

    Pete

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    Re: DAC corrections

    What amazing work in that issue of Victor. Even if one wasn't interested in the Hasselblad lens propaganda, it's worth a look!

    I was also inspired by the notion of personally shooting for the Hasselblad Masters title for Wedding/Social next year. May not stand a chance, but trying can do nothing but spur me on to the next level. Aspirational goals sometimes help give one a needed nudge.

    The article on sensors is also very interesting, and shows the challenges faced by the DB makers. Makes me want a Multi-Shot rather more pixels even more.

    Peter, I've run in studio tests comparing many of my HC lenses to my CFi & CFE counterparts ... mostly to dispel my own "carry-over myths." Since much of my paying work is indeed "In-Studio," that was a priority. As Irakly once observed when I was doing some of these tests, the HC optics are really suited and apparently optimized for this type application ... I think I agree with him concerning some (but not all) of the HC optics ... when using controlled lighting for subjects that must retain faithfulness to the subject's characteristics ... the HC 120 Macro is a perfect example of this. However, the 100/2.2 is not, and has special characteristics that take it out of the studio to compete quite well with even my FE optics.

    Yet, there are certain characteristics of some of the V lenses I still prefer for other work or personal projects. Plus the lens range of the Zeiss system is more extensive ... and/or can act as "back-ups: to the HC line of lenses. Thankfully, all those V lenses are available for use on the H cameras.

    As far as "Digital Software Corrections" AKA: DAC are concerned, I personally could care less how they arrive at it ... and if it's less expensive, then it makes better business sense on my end. I can relate practical experiences concerning this all day long.

    For example: My previous digital system was a Contax 645, and I once had a paying gig to shoot the interior of a supermarket for Unilever Foods, specifically shelves ... to make life sized prints for a walk-in convention display. Space dictated use of the Zeiss/Contax 35mm (this was a rush job with limited time allowed in the Supermarket ... so there was no time to secure a view camera, lenses, and fitted DB which at the time were not as readily available, or as easy to use as they are now.) The Zeiss 35 produced significant distortion, so piecing together the life sized walls was a post production nightmare. I would have killed for the H system with either the 28mm or 35mm employing DAC corrections. I have since done similar jobs with the H and 28mm, and post was a breeze.

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    Re: DAC corrections

    Marc, regarding difference s between HC and Zeiss lenses - it seems that Zeiss were designed to deliver their best results at infinity - and at infinity the Zeiss optics tested were at the margin better than HC.

    Interestingly, the article suggests that at more 'normal' focusing distances - the distances which the HC optics were designed for - HC formulations evidence significantly better MTF characteristics. perhaps this is in fact what Irakly was observing and related to you. A number of people have suggested to me that teh HC lenses are without a doubt the best studio set-up. Perhaps for same reason other formulations - especially when used with film are better choices in non studio settings.

    For me it was a very insightful piece of 'propoganda' if you like - enough to convince me to buy into a seperate system as an addition to HC - so I can shoot with F type lenses. -

    There are also - some very good technical explanations of why certain lens formulations will evidence front or back focus issues with digital chip capture - when the same lenses wont evidence same with film - well worth a read.

    Some of the photography was awesome I agree! I will put in my one year free subscription for sure.

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    Re: DAC corrections

    Quote Originally Posted by PeterA View Post
    For those interested in Hasselblad's aproach to lens design and in particular how DAC corrections work - you will find a very interesting and thought provoking article in the latest issue of Victor. This is an online publication.

    A number of thought provoking issues emerge- in particular the fact that high resolution digital capture makes it more diffcult for lens design to deliver super sharp images at any distance.

    Interestingly - Hasselblad point out the difference betwen C lenses and H lenses in terms of strengths and weaknesses for both.

    http://www.victorbyhasselblad.com/en...ne-/22008.aspx

    Recommended for people who prefer not to satisfy themeselves with repeating other people's BS. It seems that Mamiya is embarking on a similar philosophy with their new D spec lenses and coming corrections in Capture One.

    I would be very skeptical of third party software that does not have access to the lens maker's prottype optic algorythms in applying DAC corrections and yet claims to be able to apply same.

    Pete
    Hey Peter

    tiny bit off thread but yesterday I read the press release from Phase stating that C1 would support corrections for the HC lenses. I have the latest copy of C1 and it can't open the 3FR files let alone apply corrections to those lenses. I wonder if they are referring to a future version of Capture One?

    Woody

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    Re: DAC corrections

    Woody I think C1 is referring to Hassy lenses shot with the Phase back that they are able to make corrections for. I do see the lens selections in the C1 to pick say the Hassy 120mm and such. So it appears to be the H1 or H2 body shot with hassy glass with any of the Phase backs. For you no use but for the Phase back shooters using the Hassy bodies.

    Also for the Contax 645 shooters and Zeiss glass with Phase backs. This is a nice new feature for all the Phase back owners of different front end systems.

    So the support for Contax/Hassy/ mamiya camera's and lenses are now supported for the Phase back owners. Pretty cool

    Also I am expecting more of this when the new Pro version hits the streets next month. Hopefully implemented in time for the lighting workshop
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    Re: DAC corrections

    I only scanned it quickly, but an interesting overview of lens design strategies indeed.

    Not sure it's relevant, but I think it's worth pointing out that historically a few lens manufacturers bucked the common trend and optimized their lenses for other than infinity focus. One of the first was Leica, which IIRC sometime in the 40's realized they'd get better overall performance if their lenses were optimized to the normal shooting distances folks were commonly using their RF system at. Hence the RF framelines and lenses are optimized for 3 meters subject distance. (May be one reason we all migrated to them in the first place?)

    Rodenstock takes a slightly diferent approach and optimizes their LF lenses at specific subject magnifications, thus each focal has a different distance it's optimized for. (I can only assume Schneider does this too, but have no hard data on it.) Their APO Sironar N line is optimized for 1:20 and beyond, basically a landscape distance, while their premier lens line, the APO Sironar S, was optimized for between 1:5 and 1:10, or tabletop range. What is interesting is in field tests I did with my digital scanning back, the APO S were clearly superior in the 3 to 10 meter range, and while you could see a slight loss of performance at longer distances, they remained superior to the APO N line at infinity. IOW they were better everywhere, at least with the digital sensor...

    Moreover, the digital scanning back software allowed you to live focus on any color channels selected. In this, it was VERY apparent that many APO designated lens were anything but true APO, in that the three color channels never came to perfect focus at the same point. (Though they may well have been inside the tolerances of the thickness of film emulsion, and hence essentially true APO for film, they were not in line on a perfectly flat digital sensor.) The best ones were close with maybe two of three in synch, but frankly most were pretty far off. (FWIW, the newest offerings from Schneider and Rodenstock were generally good, and the digital specific versions very good.)

    Sorry for the digression,
    Jack
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    Re: DAC corrections

    Quote Originally Posted by Guy Mancuso View Post
    Woody I think C1 is referring to Hassy lenses shot with the Phase back that they are able to make corrections for. I do see the lens selections in the C1 to pick say the Hassy 120mm and such. So it appears to be the H1 or H2 body shot with hassy glass with any of the Phase backs. For you no use but for the Phase back shooters using the Hassy bodies.

    Also for the Contax 645 shooters and Zeiss glass with Phase backs. This is a nice new feature for all the Phase back owners of different front end systems.

    So the support for Contax/Hassy/ mamiya camera's and lenses are now supported for the Phase back owners. Pretty cool

    Also I am expecting more of this when the new Pro version hits the streets next month. Hopefully implemented in time for the lighting workshop
    Thanks Guy

    That seems a logical explanation.

    I keep forgetting about the H1 and H2 where Phase backs were pretty much the norm.

    However too bad for us H3 shooters as the lenses aren't covered. I tried to develop raw in Phocus, convert to DNG and then open in C1 4.1.2 but it won't open the DNG files either. Guess I will have to talk to Phase or Doug Peterson to see what is up with that

    Thanks for the help

    woody

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    Re: DAC corrections

    I wonder if there was a way to make them look as Phase files which is a .tif . Maybe Doug has some idea's for this
    Photography is all about experimentation and without it you will never learn art.

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    Re: DAC corrections

    Just a thank you to PeterA for posting that link. I learned something today about lens design and optimization.

    Thanks!
    Tim

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    Re: DAC corrections

    Woody - i am not familiar with C1 - yet. i will be on a position to compare DAC results in C1 vs Phocus - shortly. I will post my findings in due course.

    Jack - the whole issue of lens optimisation for optimum focus differing from lens to lens is new to me. Now I am thinking that I will do some hooby work on thsi area - as teh technologu of photography and optics is very interesting to me. Fortunately I have the math and physics background to get into it. I am thinking of it as dementia prevention startegy. -

    Pete

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    Re: DAC corrections

    Lens design and optimization- Jack good points there.

    Peter, You may want to look up the data sheets (pdfs through google from Zeiss' website) on the S-Planar 120/5.6 (Or the Makro-Planar) where it explicitly states the magnifications it is optimized for. I would also suggest Akiyama's site (mostly esoteric Nikon lenses) which summarizes the data for many special purpose lenses (all involve close range or macro lenses).

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    Re: DAC corrections

    Quote Originally Posted by PeterA View Post
    I am thinking of it as dementia prevention startegy. -


    I hear that, getting to that age myself my friend!!!
    Jack
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  13. #13
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    Re: DAC corrections

    I tried the new Hasselblad lens profiles in C1 -- they appeared to do absolutely nothing with my P30+ files. I was hoping it would help get rid of the nasty purple fringing I get in a lot of my backlit shots...

    Has anyone gotten the new C1 profiles to work for the H lenses or Contax? Just curious...

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    Re: DAC corrections

    Did you check purple fringing than hit analyze. This is not a automatic feature
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    Re: DAC corrections

    Stupid question, but did you actually check the purple fringing box in C1?
    Jack
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    Re: DAC corrections



    Okay, this posting together is getting ridiculous!!!
    Jack
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    Re: DAC corrections

    Hell where did you come in from. I just got home from dinner.

    Great minds think alike. Not
    Photography is all about experimentation and without it you will never learn art.

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  18. #18
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    Re: DAC corrections

    I compared a processed file with and without the correction (the analyze box checked), then compared both files in layers in photoshop. The files are exactly the same...no difference whatsoever.

    Has anyone else tried it?

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