topic Re: G7xii vignetting in Point & Shoot Digital Cameras

G7xii vignetting

rocketmann — Fri, 06 Jan 2017 01:57:46 GMT

Have new G7xii which exhibits severe vignetting when shooting RAW at widest angle. This is not apparent when using "Quick Look" in Finder Mac OS X Sierra. But when I import the RAW file into Affinity Photo it is quite pronounced. Have others experienced this or do i have a lens problem?

Thanks for your thoughts.

Re: G7xii vignetting

Richard — Fri, 06 Jan 2017 02:33:04 GMT

Hi Rocketmann,

Thank you for posting.

Do you see the vignetting when you view your images in the Digital Photo Professional PowerShot G7 X Mark II?

Re: G7xii vignetting

kvbarkley — Fri, 06 Jan 2017 02:34:51 GMT

Sounds right to me. The camera is correcting for the vignetting when shooting JPEG's but gives you raw, uncorrected data, for the RAW file - that is why it is called RAW. You will have to correct it in post. Canon's DPP should correct it automagically.

Re: G7xii vignetting

rocketmann — Mon, 09 Jan 2017 15:14:48 GMT

Sorry. Got cut off on previous response. A RAW file is unprocessed by the camera and gives you an unprocessed histogram. I don't use DPP anymore - too many problems with OS Sierra. I use Affinity Photo which has more controls
Anyway you don't advertise a 24mm coverage when it's not. I suspected that the vignetting was being corrected for but that is false advertising unless the corrected image is 24mm, in which case I stand corrected.Thanks for your comments.

Re: G7xii vignetting

kvbarkley — Mon, 09 Jan 2017 15:21:17 GMT

BTW, If "you" means Canon, that does not apply to me, I am just a user as yourself.

How much vignetting would mean that the lens "doesn't have 24mm coverage?" If all the other distortions were under control, vignetting is an easily correctable issue.

This really gets into philosophical territory. I recall some RAWs from a fixed lens camera (not Canon!) that were awful, all kinds of distorting and vignetting. The JPEGS were fine. But the MFG had not provided any way to get the in-camera corrections. After a lot of complaints, the company actually put the corrections in the RAW file. But was it still RAW?

Re: G7xii vignetting

rocketmann — Mon, 09 Jan 2017 15:41:44 GMT

Yeah. Sorry for the loose use of "you." I did mean Canon.

Are you saying that the corrected RAW file is a 24mm focal length?

If that's the case then I'm cool with that. But if the focal length resulting from the

corrected file is more than 24mm then Canon should advertise the lens as a 28 or 35mm.

That is not a philosophical issue it's truth in advertising. Thanks for your info. and thoughts

on my issue KV.

Re: G7xii vignetting

kvbarkley — Mon, 09 Jan 2017 15:49:58 GMT

I am not sure what you mean. The G7XII has an 8.8 to 36.8 mm lens. I am sure if you set it to 24 mm you will get a 24 mm raw file. If you set it to 8.8 mm, you will get an 8.8 mm raw file which has an equivalent field of view to a 24 mm lens on a 35mm ("full frame") camera.

Oh, and the quick look uses the JPEG preview which will have the correction for vignetting applied.

Re: G7xii vignetting

Waddizzle — Mon, 09 Jan 2017 18:29:29 GMT

@rocketmann wrote:
Sorry. Got cut off on previous response. A RAW file is unprocessed by the camera and gives you an unprocessed histogram. I don't use DPP anymore - too many problems with OS Sierra. I use Affinity Photo which has more controls

Anyway you don't advertise a 24mm coverage when it's not. I suspected that the vignetting was being corrected for but that is false advertising unless the corrected image is 24mm, in which case I stand corrected.Thanks for your comments.

Your assertions are what are false. You are conflating actual focal length, with equivalent focal length.

The stated focal length of a lens describes physical characteristics of how the lens is made. The equivalent focal length is characteristic based upon the size of the image sensor that is used with the lens. These physical characteristics are used to calculate the depth of field of the lens at different aperture settings.

Because your camera does not use interchangeable lenses, the standard descriptions may seem incorrect. In the world of cameras that use interchangeable lenses, though, the same lens can be attached to camera bodies with different size image sensors. Describing focal lengths of a lens in terms of how they are actually made, and not how they are used, allows for accurate comparison between camera bodies and lenses.

Re: G7xii vignetting

rocketmann — Mon, 09 Jan 2017 19:05:55 GMT

Thanks for clarification. So the FOVCF for the G7xii is 1.0 according to Canon. As I understand this there should be no cropping required. Is this right?

Re: G7xii vignetting

kvbarkley — Mon, 09 Jan 2017 19:13:53 GMT

I have never heard of an "FOVCF" but if it is "Field of View Correction Factor", someone lied to you . It is pretty obvious that an 8.8 -> 36.8 mm lens that has a 35mm equivalent of 24->100 mm has a 2.7 crop factor - compared to 1.6 for an APS-C lens.

You might have confused the 1 inch sensor with a cop factor of 1.

Re: G7xii vignetting

Waddizzle — Mon, 09 Jan 2017 19:21:52 GMT

@rocketmann wrote:
Thanks for clarification. So the FOVCF for the G7xii is 1.0 according to Canon. As I understand this there should be no cropping required. Is this right?

You've lost me. What is FOVCF? I am not familiar with your specification. I do not understand your comment about cropping, either.

Another way to describe the relationship between focal length and image sensor size is AOV, Angle of View, something which I have not seen specified anywhere for the G7x Mark II.

Re: G7xii vignetting

rocketmann — Mon, 09 Jan 2017 20:05:20 GMT

I think I understand what you're saying. So to bring this full circle and answer my original concern which was should I be seeing severe vignetting on my RAW files shot at 24mm the answer is yes?
Thanks for your help and yes, the acronym FOVCF is as you guessed.

Re: G7xii vignetting

Waddizzle — Mon, 09 Jan 2017 20:35:14 GMT

@rocketmann wrote:
I think I understand what you're saying. So to bring this full circle and answer my original concern which was should I be seeing severe vignetting on my RAW files shot at 24mm the answer is yes?
Thanks for your help and yes, the acronym FOVCF is as you guessed.

Whether or not you see vignetting comes from the lens. Vignetting in RAW files can be easily corrected in post-processing. The Canon software should be able to correct it. Third party software packages may not offer the support.for lens correction of a G7x II.