Distortion with Zen dome and Olympus 9-18mm - JPEG vs RAW

Since getting the Zen dome for my Olympus 9-18mm lens I have been disappointed with softness/distortion mainly towards the edges. I have just realised something though that I am surprised I hadn't picked up on sooner.

It is the JPEG images that show this distortion and it is much less evident (maybe non-existent) in the RAW images.

Here is a link to an example. If you flick backwards and forwards between the two images quickly the distortion of the diver in the left corner becomes quite obvious.

https://picasaweb.google.com/118038872344502304872/LensDistortion?authkey=Gv1sRgCKemycSdo8LQBQ#

I am a bit puzzled by this as it seems to be the opposite of what happens above water. My understanding is that the Olympus cameras correct for any barrel distortion in the JPEG. I have seen this in my photos where for example an horizon may be straight in the JPEG photo but curved in the RAW equivalent. This leaves me wondering if somehow the dome is 'tricking' the sytem and the camera is causing distortion rather than correcting it?????

Have others noticed this issue and any thoughts on why it is just the JPEG where this is happening?

Looks like I am going to have to improve my Photoshop skills so I can stick with using the distortion free RAW images!

I can’t see your photos. But sounds like the JPG software is applying some lens correction to the lenses inherent distortion, which is causing the softness.

Alex

Thanks Alex.

Following on from your reply I am wondering if the dome port is maybe already correcting for the inherent distortion of the lens and then the JPG software is applying a correction that isn't necessary and thereby actually creating distortion. Or maybe the dome in combination with the 9-18mm lens is creating a distortion that is just inherently different to what would be normal above water and so the software 'mis-corrects' it.

This leaves me wondering if this may also be an explanation for the mixed reports I have heard about the Zen dome. Some say it is great and others complain about soft edges. Maybe those that are using RAW only are getting distortion free images while someone else using JPEGs only would be getting distorted images.

The photo above is JPEG. And the one below is RAW. Hopefully the distortion of the diver will be visible in the JPEG compared to the RAW.

(Not my best photos by the way but it illustrates the point I'm making)

My understanding of how this is supposed to work is that embedded in the RAW are the parameters that allow Lightroom (and others?) to make a correction to the image. While in the JPG the camera has already made those corrections. Perhaps Lightroom with more time does a better job? That said, I don't really see what you are saying from the images you posted.

Me either can't see a big distortion, it looks as the JPG is a bit cropped.

In any case you should switch off any image modifying camera "tweaks" and record in RAW,

this enables you to modify the images as you like and not what the camera brand engineers believe to be good.

You need Adobe Lightroom and not Photoshop, Lightroom is for 90% of the tasks more than enough and in case you need to do some heavy "tweaking"

you may use the excellent and free GIMP.

I personally don't like Lightroom's lens correction as i find that usually it degrades the quality of my Nikon D800 pictures, except the picture has a lot of uniform colored water.

Chris

Thanks for the further feedback.

For some reason the distortion isn't as evident when I posted the photos directly on here. It is more evident in the original link I gave as you can flick quickly between the two images and it becomes more obvious. Alex said he couldn't see the images so I'm not sure why the link doesn't work for him, but here it is again in case others can see it: https://picasaweb.google.com/118038872344502304872/LensDistortion?authkey=Gv1sRgCKemycSdo8LQBQ#

I see it. The diver gets fatter. Also focus on the pupil of the diver. Definitely sharper in the raw image.

What software are you using to process the raw image and is that software aware of the fact this is a 9-18?

I can't really see the difference between the two that well (some), but I found the distortion in RAW as well. Two weeks ago was my first trip with this camera and lens underwater, this was shot at 9mm, zen dome, no cropping and definite corner distortion (NB, this was even using the +2 dry diopter some recommend)

processed in LR

Thanks Alex.

 

Following on from your reply I am wondering if the dome port is maybe already correcting for the inherent distortion of the lens and then the JPG software is applying a correction that isn't necessary and thereby actually creating distortion. Or maybe the dome in combination with the 9-18mm lens is creating a distortion that is just inherently different to what would be normal above water and so the software 'mis-corrects' it.

 

Probably no.

The geometric distortion correction can not analyze the image in any way.

Was this Zen port specific for the Olympus 9-18? Or a wider, more curved dome for fish-eye? I'm curious because I just picked up a 9-18 and I wonder how it might fare with a fisheye dome, which I already have for the Panasonic 8mm. The good people at Bluewater Photo say that image quality at the edges will likely be pronounced.

Was this Zen port specific for the Olympus 9-18? Or a wider, more curved dome for fish-eye? I'm curious because I just picked up a 9-18 and I wonder how it might fare with a fisheye dome, which I already have for the Panasonic 8mm. The good people at Bluewater Photo say that image quality at the edges will likely be pronounced.

Yes, I am using the Zen dome specifically intended for the Olympus 9-18 lens.