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Lens Profiles - General discussion

Denis Mortell
I use four lenses a lot.

Canon 50mm Macro
Canon 45mm Tilt/Shift
Canon 17-40mm Zoom
Canon 90mm Tilt/Shift

For walk-about, I use a Sony RX-100. (There's been quite a bit of discussion about this camera here. Do a search.)

I'm coming to C1 from Lightroom - or at least I'm trying very hard to, because it's an incredible program - except for its lens profiles.

Simply put, the lens profiles in LR are better, and when they're not what you'd like them to be (extremely rare), the tools to correct them are there. They don't in C1 - unless I'm missing something.

While I have no issues with the 50mm macro in C1, nor the 45mm t/s, the 17-40mm is simply unacceptable, and I have to process anything in LR. The LR profile for this lens is flawless. Why can't the C1 profile be so?

Failing that, to have the comprehensive set of tools to correct manually (as LR has) would be nice.

Is C1 first and foremost about looking after PhaseOne lenses? I hope not.

I'm surprised there hasn't been more discussion about this issue, which is why I'm starting this thread.

Any comments welcome.

Thanks.

D.
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Comments

13 comments

Date Votes
  • Ian Wilson
    Moderator
    Top Commenter
    Could you say a bit more about what in the profiles isn't what you would like it to be, and what aspects you would like to be able to adjust manually if you needed to (chromatic aberration? distortion? light fall-off?).

    Ian

    Edited to add - you can't always properly see the effect of things like the adjustment for chromatic aberration or purple fringing until you view the image at 100%.
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  • SFA
    I would echo Ian3's post.


    To simply say that something is not acceptable without any attempt at explaining why you have that opinion is of no use to anyone.

    Moreover if you have specific concerns on what is a technical subject I would have thought the first thing to do would be to check with Phase about the problem you think you have. Did you do that? What did they say? How do you know that solutions offered by other systems are "flawless". Have you checked the lens calibration yourself?

    From what I understand of the process that Phase go through to assess a lens there is little that users on a User to User forum could contribute to calibration (that would be of much help to anyone else).

    More surprisingly perhaps, from a user perspective in a user forum, the lens for which you specifically pick out a profile for criticism is probably in quite common use yet I don't recall any previous comments about the profile being "unacceptable". That is perhaps a little odd, as you point out, given how many people are usually willing to offer critiques.

    What gives you the impression that the 50mm Macro and 45mmT/S are OK whereas the 17-40 is not?



    Grant
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  • Denis Mortell
    Sincerest apologies for not being clearer in my original post.

    My problem with the 17-40mm profile is pincushion distortion.

    I have no issues with CA, vignetting or fringing.

    The pincushion distortion is slight, and I can correct it. But, being a zoom lens, the amount varies depending on the focal length. So, making multiple corrections is not practical in my workflow.

    I note, for what it's worth, that the default setting for Distortion, with the 17-40mm files, is 0%.

    When the lens is very wide, I lose a little of the edges that are retained in LR. And that translucent grey banding appears.

    With the RX100, the default Distortion setting is 100%. Pincushion distortion is present, more often than not, and requires a reduction of the Distortion % to fix it, in my experience. Also, the amount of pincushion distortion varies greatly, depending on the focal length.

    Regarding the grid overlay in C1: I note that it kicks in when you click on the Distortion button.

    1. Is it possible to have it on all the time? I could then drag a straight line in the image next to a grid line to ease the correction process.

    2. Is it possible to increase the number of grid lines?

    Thanks.

    D.

    Ps. Changes made to rotation and distortion can reveal that translucent grey banding around the edge of the image. What's the point of it? Is it possible to turn it off? Is there an equivalent to LR's Constrain Crop? Thanks.
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  • SFA
    OK, much easier to understand and discuss. Thanks.

    Thinking of the RX100 - I'm not sure but I would guess that for compact cameras at the usual way to adjust would be to apply values for correction provided by the manufacturers. They know what they have compromised on in the lens design and fully expect to have to apply corrections.

    I have a Canon S90 which is not listed for C1 support but, afaik, has the same lens as the S100 (or near enough) and that is listed. So if I am using it at the wide end and want correction I just use an alternative profile. At the long end (actually from about half way) there is little or no correction needed. I also have a G11 which seems to work the same way.

    My interpretation is that all lenses are measured at their available zoom levels (often somewhat stepped rather than continuous) and fstops and where significantly different values are required step by step they are recorded and applied based on the Exif information supplied for the image. I think I am right in saying that for any setting where there is an adjustment assessed as required it will be applied and the lens adjustment tool will always show 100%. I.E. that particular set of adjustments assigned to the lens settings in the EXIF data are being applied 100% but one can change that if preferred.

    If I am fundamentally wrong someone please let me know so that I can enhance my understanding.

    If the % adjustment shows as 0 then typically, in my experience, no adjustment values have been deployed. Whether they should have been is another matter ...


    If you always see 0% at all focal lengths for your 17-40 f4 L then, given someone has taken the time to create a profile for it which suggests there may well be some correction to be enjoyed, something rather strange might be going on.

    The question about what is or is not cropped from the image by lens correction is another challenge in its own right and has been discussed before though some time ago now. Right now I think we should be looking at your 17-40 challenges first and considering what is or is not cropped second since the first part usually influences the second part.



    Grant
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  • Paul Steunebrink
    [quote="Dinarius" wrote:
    ...
    Regarding the grid overlay in C1: I note that it kicks in when you click on the Distortion button.

    1. Is it possible to have it on all the time? I could then drag a straight line in the image next to a grid line to ease the correction process.

    2. Is it possible to increase the number of grid lines?

    Yes, to both questions. See the Preferences, Crop tab. The number of grid lines can be set there. Grid lines can be made visible with the Show Grid and Guides feature (button and from View menu).

    The guides can be moved.

    By the way, I always use some Canon images made with 17-40mm L lens for demonstrating lens correction in classroom trainings, in particular the correction at the wide end. I recall a distortion setting of 100% by default..?
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  • Denis Mortell
    Paul, Grant,

    Many thanks for the replies.

    I've gone through a random selection of folders of files shot over the last twelve months and, in all cases, the 17-40mm default Distortion setting is 0%.

    I'm Windows 8 x64bit. Are you Mac, by any chance? If so, might this be the difference?

    I'm not using Sessions or Catalogs, only a generic (if that's the word in this context) Session. Would that make a difference to the % setting?

    That said, if I move the Distortion slider to 100%, what I'm seeing looks better than the 0% default.

    Finally, I've adjusted the number of lines in Preferences. Thanks.

    (For some reason, adjusting the number of lines in the Horizontal box, increases the number of vertical lines on the image and vice versa. But, maybe this is the way it's meant to work. )

    Thanks again.

    D.
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  • Christian Gruner
    Let me explain how are our lens correction tool works in broad terms:

    - For a given zoom, let's say the 17-40L, we measure distortion and other parameters for each of the printed focal length markings, plus in intervals in between these steps.
    - If the lens distort under a certain threshold, no distortion-correction will be applied automatically. Above the threshold it will. In the past, this threshold was higher, but customers wanted this a lower, and we listened.
    - No correction is applied with the slider a 0%.
    - When we apply the lens correction (when the slider is at more than 0%), we are taking aperture (for light fall-off) and and the focal-length into consideration.
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  • Denis Mortell
    [quote="Christian Gruner" wrote:

    - When we apply the lens correction (when the slider is at more than 0%), we are taking aperture (for light fall-off) and and the focal-length into consideration.


    Thanks for the reply.

    So, when Paul says he is seeing 100% Distortion correction, he must be using an aperture different to mine (typically f11 in my case) since the 17-20mm range, where I would expect to see distortion and therefore correction applied, is what we're both using, but seeing a different % correction - 0% in my case, 100% in his.

    D.
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  • Christian Gruner
    He is probably using a different focal-length. The aperture doesn't affect the distortion.
    Usually a lens distorts more in the lower focal-lengths.
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  • Denis Mortell
    [quote="Christian Gruner" wrote:
    He is probably using a different focal-length. The aperture doesn't affect the distortion.
    Usually a lens distorts more in the lower focal-lengths.


    Ok. I try the lens at a few different focal lengths and see if the Distortion slider defaults to 100% at any of them.

    Thanks.

    D.
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  • SFA
    [quote="Dinarius" wrote:
    [quote="Christian Gruner" wrote:
    He is probably using a different focal-length. The aperture doesn't affect the distortion.
    Usually a lens distorts more in the lower focal-lengths.


    Ok. I try the lens at a few different focal lengths and see if the Distortion slider defaults to 100% at any of them.

    Thanks.

    D.


    One other possibility that comes to mind (there may be others too ....) is that you have unintentionally set a Default adjustment for the lens that has the adjustment amount set to 0%. Or something like that.

    Could that be a possibility?



    Grant
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  • Paul Steunebrink
    Question: the images made with the 17-40mmL lens, have they been opened with an earlier version of CO, like CO6? Although not tested recently I have seen several occurrences in which old adjustments, previous CO engine (typically CO6 engine) did not recognise the lens profile properly.

    If this is the case, create a new variant and see whether anything changes.

    I emphasize I have not tested this recently. I tested today with some 17-40mmL shots (made with a 1D mk2) and images on the wide end (17mm) are corrected very well automatically in CO 8.1 on Windows, distortion slider at 100%. At the long end, the distortion slider is 0%.
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  • Denis Mortell
    Paul, Grant,

    Thanks for the replies.

    I shot a file at 17mm and read it straight from the card. It's showing at 100% distortion correction, which is good.

    Is the CA boxed ticked by default? If not, where would I have set it as a Default?

    Think I'm ready to make the switch to C1 now. 😎

    Thanks again.

    D.
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