New Tutorial: Improve Image Quality with Lens Corrections

[McQ]

There's a new tutorial...

Improving Image Quality with Lens Corrections

These can make an enormous difference with image quality -- especially with compact cameras and inexpensive lenses. For best results though, it's something that should be used with nearly every camera.

before and after chromatic aberration example at 100% on right

This tutorial includes a mix of technical and applied topics. It also tries to provide a basis for why each type of imperfection can happen without resorting to lots of lens diagrams. Even if you're already familiar with topics like distortion and vignetting, also take a look at the CA section for an overview of the different types. For example, did you know that you can change the visibility and color of axial CA by slightly front or back-focusing your lens?

As usual, please let me know if you feel anything is unclear, if you notice any typos, or just want to add something from your own experience.

Many thanks!

[pat3pee]

I don't know if I'm in the right THREAD but I wanted to share this web link with you who want to get the best out of the (post processing ) photos...You can download and use it free for a month.

http://www.dxo.com/intl/photography/...onfirmation-en

Cheers / Patrik

[patrickjohnson]

The Photo shopping is not bad. It looks like you've done a pretty good job as far as technique goes.

[pnodrog]

Hi Sean it is a very good addition to the tutorials. It is well presented and easy to understand.

I am not sure how many photographers are aware of the impact and future possibilities that software correction of the short comings of a lens may ultimately have on it's design, performance and cost. Expensive, supremely engineered but bulky lenses may end up having their performance virtually matched by lighter and cheaper lenses that can have their design compromises corrected to a large extent in PP.

P.S. It is possible that some of the super-zoom compacts are already incorporating some form of in camera lens correction software to improve the apparent optical performance. (Hence the reluctance to provide RAW files?)

[RichardTaylor]

Thanks very much for this tutorial.

[Mike Buckley]

The tutorial is very clear and easy to understand.

I found two minor issues in the first paragraph explaining lens correction profiles:

Many modern RAW development software
While that use of the plural form of "software" is probably accurate, a lot of people including me apparently find it odd. You might want to consider changing "software" to "software applications" or "software programs."

This can be an enormous time-saver
No hyphen is needed in "time-saver." "Timesaver" without the hyphen is listed in many online dictionaries (though the spellchecker built into Firefox thinks it's not a word).

[DanK]

A nice tutorial--clear and very useful for folks who aren't familiar with these corrections.

I have one suggestion. This is how the disadvantage of correcting for vignetting is described:

"However, correction will increase image noise toward the corners, since this works by effectively applying a radial graduated neutral density filter."

I'm willing to wager that almost no one at the level of expertise for which this tutorial is most useful will understand what this means. Even if one knows what a radial graduated neutral density filter is, this doesn't tell the reader why applying one increases noise. I suggest dropping the clause about the filter and instead explain that the correction works by brightening the affected areas, which amplifies the noise in that area as well as the signal.

[Mike Buckley]

"However, correction will increase image noise toward the corners, since this works by effectively applying a radial graduated neutral density filter."

I'm willing to wager that almost no one at the level of expertise for which this tutorial is most useful will understand what this means.

Completely agreed.

[Colin Southern]

Keep in mind folks that Sean's article & post was around 2 1/2 years ago.

[Mike Buckley]

Keep in mind folks that Sean's article & post was around 2 1/2 years ago.

Ahhhh. That being the case, why is it suddenly showing up as a "new" post?

Even so, the fact that the original post is 2 1/2 years old doesn't render the suggestions being made irrelevant or unhelpful. Hopefully Sean still appreciates the input and is willing to seriously consider acting upon it.

[Colin Southern]

Ahhhh. That being the case, why is it suddenly showing up as a "new" post?

Patrick Johnson posted to the thread yesterday.

Hopefully Sean still appreciates the input and is willing to seriously consider acting upon it.

I very much doubt that he'll see it.

[Mike Buckley]

I very much doubt that he'll see it.

Maybe you should bring it to his attention.

[Colin Southern]

Maybe you should bring it to his attention.

Or maybe you should.

[Mike Buckley]

I just now sent a short note to him.

[Colin Southern]

I just now sent a short note to him.

[Mike Buckley]

Your best photo yet, though the catch lights look more like a cartoon than a photo.

[McQ]

Mike and Dan: thanks for all the feedback! Everything you two have shared has now been incorporated in the online article. These will eventually be going into an eBook, so I am always looking for ways to improve the text and keep them up to date.

[Bama]

Just a question on the tutorial: you indicate that Aperture has lens correction capability. Specifically you state that

"Many modern RAW development software has the ability to perform lens correction using pre-calibrated parameters for a broad range of camera and lens combinations. This can be an enormous time-saver if available. Adobe Camera RAW (ACR), Lightroom, Aperture, DxO Optics and PTLens all have this capability in their most recent version."

How does one access it in Aperture? Or is it done automatically? Thanks, it is a helpful addition to the Cambridge tutorials.