Canon Community Canon Community
 


Reply
Frequent Contributor
Posts: 64
Registered: ‎02-13-2018

Some lens correction questions

Having looked through the various user manuals associated with the subject software there is very little information that helps to inform a user just learning about digital image processing what's being done.  As best I can tell lens correction is something that only applies to the raw (i.e., as yet undeveloped) data.  DPP4 has a tab in the editor called "Perform image lens correction".  With that tab selected there is a tool called "Digital Lens Optimizer" that appears to depend on having access to data specific to the lens in question.  I was able to exercise the control that finds the data and turns the "Lens Data" indicator from "No" to "Yes".  Now what?  The controls for the various tools are pretty straightforward but what is supposed to happen when they are used is not described?  In that, what to look for?  So far I've played with them a bit but cannot say that I've noticed any affect.

Moving on to the EOS Utility, it appears as though it can be used to either add or remove lens correction data to the camera.  Apparently the camera is preloaded with data for some lenses but, depending on the lens/es being used, it may be necessary to add data for the lens/es being used.  I presume that removing data for unused lens/es might be necessary because of capacity restrictions but that is only a guess.  I didn't notice anything in the user manuals about this idea.  Apparently there are some complications (i.e., differences) based on the kind of camera/s being used.  The user manuals refer to "Lens aberration correction data" which appears to be applicable for all cameras.   Then there is also something called "DLO" with no mention of what that term (e.g., ? acronym) means.  Another guess is that it might be "Digital Lens Optimizer", which in this case may only apply to certain cameras.

Insofar as this lens specific data is only used when processing raw data, I'm also guessing that it needs to be present in the camera if it is to be used by the camera when producing images in .jpg format.  Another guess is that this lens specific data that is loaded into the camera has no affect on the raw files produced by the camera.  Since an idea that I've had up to now is that DPP4 is able to produce a .jpg file equivalent to what the camera can produce without the need for any editing on the users part, I'm now pretty confused.  In that, when initially installed DPP4 seems to have no lens correction data until it is added (e.g., ? downloaded) by the user.  Since, it appears that my lenses are among those that have no lens correction data pre-installed in the camera I'm thinking I might be lucky enough to be getting equivalent .jpg images from either DPP4 processing a raw file or the camera produced .jpg file but what about all those lenses that appear to be pre-installed in the camera?

Finally, with all of that said, my present method is to produce raw files in the camera and then develop them myself using software like DPP4 as well as other, primarily open source, software such as GIMP and Rawtherapee.  I'm thinking it should not matter in this case what lens correction data is present in the camera.  In that, one only needs to worry about having the correct lens specific data installed in the camera if they want it used by the camera when producing .jpg files.  Is this notion valid?

My apologies for the number of words but hope my concerns are clear.  Where I've often mentioned my need to guess it would be great if those of you who know for sure could straighten me out.

Esteemed Contributor
Posts: 3,309
Registered: ‎02-17-2016

Re: Some lens correction questions

You are correct, lens correction data only needs to be in the camera for  JPEGs. RAW files are handled by DPP4.

 

But, if you want to see what the lens correction looks like in camera*, you need to have the correction installed.

 

*And have it applied to the embedded JPEG preview in the RAW file

Honored Contributor
Posts: 5,714
Registered: ‎11-13-2012

Re: Some lens correction questions

In general you are correct. I can only speak for my camera; the camera manual explains the camera settings and indicates when DPP can provide a greater range of adjustment.

There is a wealth of information available on the Canon Digital Learning Center website.

You will maximize your capability to use Canon specific adjustments by using lens correction data and RAW conversion to a TIFF file in DPP. Then you can do further processing, including localized adjustments, in other software.

Sone folks prefer the RAW conversion in Lightroom. Nothing wrong wirh that, but you lose all capability to use any Canon features like DLO, Picture Styles, etc.

But, the bottom line is getting images that please the maker. All the various products on the market obviously please enough people to make them viable.
John Hoffman
Conway, NH

1D X, Rebel T5i, Many lenses, Pixma PRO-100, MX472, LRCC Classic
Frequent Contributor
Posts: 64
Registered: ‎02-13-2018

Re: Some lens correction questions

[ Edited ]

Thanks!!!

 

Sounds like my intuition was not too far off.  I'm not knowledgeable or experienced enough to have any strong preference for digital editing software.  However, because of the camera specific integration, I've definitely been thinking that I should do the initial raw conversion with DPP4.

 

As mentioned previously, I had been operating on the assumption that for a starting point DPP4 would develop a raw file in the same manner as the camera.  Some other posts of mine pertained specifically to wanting to know how to figure out what development operations DPP4 performs on the raw data unbeknown to me (the user).  However, since I now think I've learned that DPP4 requires the user (me) to download and install the lens specific data, when the camera might come with it preinstalled this (equivalence between DPP4 and camera development) is not always possible and therefore should not be assumed.  Is this valid reasoning?  Is it possible that there really is NO strong relationship between camera developed images and the starting point for DPP4?

 

Esteemed Contributor
Posts: 3,309
Registered: ‎02-17-2016

Re: Some lens correction questions

I think that lens corrections are johnnie-come-lately corrections in the RAW file. All the other picture setttings should be honored by DPP. I believe that you automagically get all the lens data as part of DPP, no other downloads are necessary.

Esteemed Contributor
Posts: 4,954
Registered: ‎06-25-2014

Re: Some lens correction questions


@aajax wrote:

Thanks!!!

 

Sounds like my intuition was not too far off.  I'm not knowledgeable or experienced enough to have any strong preference for digital editing software.  However, because of the camera specific integration, I've definitely been thinking that I should do the initial raw conversion with DPP4.

 

As mentioned previously, I had been operating on the assumption that for a starting point DPP4 would develop a raw file in the same manner as the camera.  Some other posts of mine pertained specifically to wanting to know how to figure out what development operations DPP4 performs on the raw data unbeknown to me (the user).  However, since I now think I've learned that DPP4 requires the user (me) to download and install the lens specific data, when the camera might come with it preinstalled this (equivalence between DPP4 and camera development) is not always possible and therefore should not be assumed.  Is this valid reasoning?  Is it possible that there really is NO strong relationship between camera developed images and the starting point for DPP4?

 


I suppose so, but you're overthinking this. The camera and DPP4 use the same lens correction data, and it comes from the same place: the Canon Web site. DPP4 can download it directly, and the EOS Utility can download it and install it in the camera. (The camera may or may not come with some lens correction data already installed, but you can find and install it for any Canon lens.) The camera uses the correction data to generate a JPEG file (if that's what you're shooting) and to display the image on the LCD screen. The embedded JPEG in the RAW file may incorporate the corrections, but the actual RAW information is not affected. DPP4 uses the correction data to generate JPEG images and retains it in the RAW file as a reversible correction. That's pretty much all there is to it. I think you're worrying about things that will take care of themselves, once you've told DPP4 and your camera what lenses you have.

Bob
Philadelphia, Pennsylvania USA
Esteemed Contributor
Posts: 4,954
Registered: ‎06-25-2014

Re: Some lens correction questions

[ Edited ]

@kvbarkley wrote:

I think that lens corrections are johnnie-come-lately corrections in the RAW file. All the other picture setttings should be honored by DPP. I believe that you automagically get all the lens data as part of DPP, no other downloads are necessary.


You tell DPP4 what lenses you have, and it will go and get the necessary correction data (assuming that you're connected to the Internet).

Bob
Philadelphia, Pennsylvania USA
Frequent Contributor
Posts: 64
Registered: ‎02-13-2018

Re: Some lens correction questions

[ Edited ]

It looks to me like DPP4 knows what lens was used. Presumably from metadata. However, even for the case where the lens correction data is preinstalled in the camera it is NOT available in DPP4 until downloaded by the user. While this was pretty easy to do I've been using my camera and developing pictures for about a year before I became aware of it (i.e., it is not automatic).

Also the few pictures (raw files) I've now developed, where I have consciously used it, I'd say the affects have been unnoticeable. I'm guessing there are a couple of possible explanations for that. First is that it is more significant it some lens than others and I happen to be using ones where it is less significant. Second, it is a bigger factor on some scenes than others and the ones I've worked on don't fall into that category.

However, I'm inclined to think that the idea of lens correction comes from knowing with certainty what the lens is not perfect and that the deficiencies are known. Therefore, it seems like the lens correction ought to generally/always be applied even if the affect is NOT apparent. An exception of course would be involved if doing so causes an apparent undesired affect on the image.

If that is valid it then leaves me scratching my head when it comes to operating the slider associated with the tool. It seems there is a range from 0 to 100 percent that can be applied. I'm puzzled about how the camera makes that choice. Yes, possibly overthinking again. I just like to know how things work which of course I also realize is impossible when working with any information technology.

Esteemed Contributor
Posts: 3,309
Registered: ‎02-17-2016

Re: Some lens correction questions

Remember, though that the lens correction is for some random lens Canon had, not *your* lens. While Canon's repeatability is getting very good (cf Lens Rentals Blog) you still don't know how well it corrects for your lens.

VIP
Posts: 8,059
Registered: ‎08-13-2015

Re: Some lens correction questions


@aajax wrote:

If that is valid it then leaves me scratching my head when it comes to operating the slider associated with the tool. It seems there is a range from 0 to 100 percent that can be applied. I'm puzzled about how the camera makes that choice. Yes, possibly overthinking again. I just like to know how things work which of course I also realize is impossible when working with any information technology.


DPP has a slider [forget the name of it]. associated with lens correction, so that you can dial in your own lens correction for lenses that are not in your catalog of downloaded lenses.  In other word, it can be useful with third party lenses.

 

With that said, you cannot use both the slider to apply correction and correction data from the downloaded lens catalog.  If you have downloaded lens correction data from Canon, just simply enable it.  Once you start adjusting the slider, you are overriding the Canon lens correction data, and applying your own.

----------------------------------------------------------------------------------------------------------------------------------------------------------

"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
powered by Lithium

LIKE US on Facebook FOLLOW US on Twitter WATCH US on YouTube CONNECT WITH US on Linkedin WATCH US on Vimeo FOLLOW US on Instagram SHOP CANON at the Canon Online Store
© Canon U.S.A., Inc.   |    Terms of Use   |    Privacy Statement