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A6600 + 18-135mm/f3.5-5.6, Image problem at 18mm


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Hi Guys,

I was shooting some flowers today. when I checked the images back home, I found out that all images in RAW format with 18mm focal length had heavy image distortion and were black-cornered. I wonder if this is the same case for you guys?

If so, 

is this issue solvable? if so, how did you guys solve it?

2. can I still use any focal length that's larger than 18mm( ex. 16mm) on this camera body?

 

 

Note:

Len is Sony's 18-135mm OSS

only images that had a focal length of 18mm had this problem only in RAW format. the same image in Jpeg did not get affected

 

Here are some sample images for your reference:

https://drive.google.com/file/d/10-I9wUBPo9KT-aaW7Fhtx2v9WCnJ3vbT/view?usp=sharing

https://drive.google.com/file/d/10-I9wUBPo9KT-aaW7Fhtx2v9WCnJ3vbT/view?usp=sharing

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10 hours ago, williamlizihao said:

I found out that all images in RAW format with 18mm focal length had heavy image distortion and were black-cornered. I wonder if this is the same case for you guys?

If so, 

is this issue solvable? if so, how did you guys solve it?

2. can I still use any focal length that's larger than 18mm( ex. 16mm) on this camera body?

For modern lens design, this is totally normal behaviour. To minimize size and weight of the lens and to improve many optical aspects, compromises are made in areas where the image can be corrected digitally. Distortion is one of these compromises: heavy barrel distortion is very common at the wide end of the focal range, up to a point where the corners of the sensor are not even covered by the projected image (i.e. rendered black). This is fixed by applying the proper distortion correction in your RAW editor: the black corners are stretched to a point beyond the image crop. Any leftover vignetting is then also digitally corrected. All this is done in-camera when processing a JPEG image, which is why it only shows up in RAW files.

2. Yes, these black corners are a property of the lens, not of the camera.

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I have this lens and yes, it is normal if you shoot raw. Actually, what I discovered is that the lens is a little bit wider than 18 mm at the short end, and when shooting jpg, the image is slightly cropped, with still some residual distortion that I seldom correct, except for architectural pictures.. 

I totally agree with Pieter, the way lenses are designed has changed with the advent of digital cameras. In the old days of film, distortion, chromatic aberration and vignetting could not be corrected, especially when shooting slide film. This was not an issue with prime lenses, but was a major obstacle to zoom lenses development, up to the point tha magazines of the time warned against zoom lenses with more than 2-3X range. 

Today lenses are designed as Pieter said, compromises are managed by software and this is even more evident in smartphones and compact cameras, which intentionally have no raw option.

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