D-Lux 8 - unexpected observation

[Leicoll]

Advertisement (gone after registration)

In some recent photos I got some vignetting when on the widest zoom setting. My camera has a B+W MRC nano filter fitted, together with a JJC LH-43LX100 lens hood. These are the resulting images in RAW and associated JPEG respectively.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Of course, the vignetting doesn't show in the finders. Removing the lens hood virtually eliminated the vignetting, but the filter must still give rise to a little.

I was a little surprised by this, but understandable. What I find most curious is that the camera processing to get the JPEG appears to introduce distortion and cropping, rather than correct it. Whereas the RAW shows proper delineation, the JPEG appears to be distorted, e.g. note the chimney and the distorted balls on top of the pillars! Is there something I am missing here?

I used DxO for examining the files.

Ian

 

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[jaapv]

You are seeing the vignetting correction in the JPG. 

[Leicoll]

I may say that is an odd way to correct vignetting. Surely, correcting vignetting is achieved by lightening the corners, not by distorting the frame into the corners and cropping. Apart from anything else, I would have thought that the JPEG would be a result of correcting any existing lens distortion, not introducing it.

Perhaps I need to experiment a bit more to understand exactly what is going on.

Ian

[ljclark]

23 hours ago, Leicoll said:

I may say that is an odd way to correct vignetting. Surely, correcting vignetting is achieved by lightening the corners, not by distorting the frame into the corners and cropping.

I don't know how "smart" the software it, but in the case of the two left corners, there is nothing to lighten in the corners.  At best you might end up with a cloudy looking mass somehow pulled out of what looks like a solid color.  If I am faced with such a noticeable incursion into the picture space, my first instinct would be to manually crop unconstrained and orient in DXO with the Crop and Horizon controls.  Other than an academic exercise, this shot might not be worth salvage...Or it may find new life with a new cropping.

Apart from anything else, I would have thought that the JPEG would be a result of correcting any existing lens distortion, not introducing it.

If you are doing post-processing in DXO PhotoLab, you might need to use some combination of Crop, Distortion, Perspective, and Volume Deformation.

Perhaps I need to experiment a bit more to understand exactly what is going on.  Good idea!

Ian

 

[Leicoll]

I've been looking at this in more detail, and have come to the following conclusion. Further to a post by @ljclark in a later thread, in relation to lens distortion, distortion is significant at very wide angle, but this is corrected within camera for jpegs. In the image I posted above, this correction does result in the chimney leaning outwards. This is the same result I get when the DxO optics module is engaged. So, I must conclude that the remaining apparent distortion is not being introduced by the camera correction, but is a natural consequence of the wide angle. Additionally, this puts the lens hood vignetting virtually out of frame.

Ian

[ljclark]

2 hours ago, Leicoll said:

I've been looking at this in more detail, and have come to the following conclusion. Further to a post by @ljclark in a later thread, in relation to lens distortion, distortion is significant at very wide angle, but this is corrected within camera for jpegs. In the image I posted above, this correction does result in the chimney leaning outwards. This is the same result I get when the DxO optics module is engaged. So, I must conclude that the remaining apparent distortion is not being introduced by the camera correction, but is a natural consequence of the wide angle. Additionally, this puts the lens hood vignetting virtually out of frame.

Ian

Wide lenses often require a little more "attention" with regards to the orientation of the camera.  The shorter the focal length, the more you see what some call distortion.  This shows in vertical lines at the edges of the frame as you tilt the camera up or down.  Our D-Lux 8s have a 24mm (35mm full frame equivalent) field of view.  It helps to keep the plane of the sensor vertical as a starting point when you compose. 

You can experiment inside your home by looking at your walls, corners, and ceilings at 24mm whilst tilting the camera up and down.  Turn on the camera's level and pay attention to the little horizontal red bar that goes up and down in the frame between the green "level" bars.  As you move the camera around tilting up or down, pay attention to the relationship between the rooms' corners and the left and right edges of the frame.

24mm is where these factors begin to come into play for many photographers.  I have an 8mm lens for my Fujifilm X cameras and I really need to pay attention whilst composing.  I use the LCD display much more often with that lens because my brain seems to process the framing there differently looking at the LCD instead of using the EVF.