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Blotchy Backgrounds ! (1 Viewer)

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Pete007

Well-known member
Occasionally while taking photographs of Butterflies etc using a 100mm macro lens the occasional image will have a background which has area's which I can only describe as 'blotchy' .
These are always out of focus backgrounds and I am not sure why these do not appear as nice and 'smooth' .
Noise shouldn't be a problem (typically iso 400-500) and I am using a Canon 100mm L macro lens so image quality is not the issue.
I very often use a Macro ring flash although I have not determined wether it only occurs when using the flash ( but cannot see any reason why it should).
I notice that it is mostly obvious with green / dark backgrounds but these are the majority of backgrounds anyway.
I have attached an unprocessed image trying to illustrate what I am describing and would appreciate any feedback concerning -
a/ What causes this or why doesn't the area appear nice and smooth… and
b/ What is the best way to overcome this and blend these area's during Photoshop processing

Any help or feedback much appreciated.
 

Attachments

  • Background.jpg
    Background.jpg
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I've no experience, but that looks like it's caused by the ring flash not lighting the centre of the image fully, to me.
 
Three questions a) This is full frame, uncropped ?
b) What was the background - grass assorted leaves etc?
c) You didn't have any auto HDR or other enhancing feature switched on?

It looks vaguely similar to the problem you had with skies back in Feb 2012 but with different colours.

If the sample is cropped (but unprocessed) image from a full frame it would be useful to see the full frame.

My theory is that the contrast difference between the correctly exposed foreground and the underexposed background means that the background is way off the comfort zone of your cameras sensor/processing engine.
Under these conditions you get noise. I have just shot a book cover as an unerexposed background replicating your conditions and got some lovely chromatic orange brown noise on a nominally green area that is very close to your example. ISO 160 on Pana G5 which was the nearest camera at the time.

It will be worse with ring flash as there is great contrast difference between your subject and the distant background.

If the sample is full frame it would be interesting to know what it was you were shooting and what your settings were to hopefully be able to replicate.

Corrective action depends a bit on the original image but can be a bit of a pig - once used an Oly E-620 with its 'shadow adjustment' switched on at the wrong time and had several pics that I actually reshot.
 
Last edited:
Thanks for the input but just to clarify I should probably just add the following points.
1/ The attached photo is actually just a cropped area from the original to better illustrate the issue
2/ That said it is still visible when looking at the original unedited jpeg or raw file
3/ Background in this example was leaves/ grass etc
4/ Regards camera processor camera used in this example was a Canon Eos 1D mk4




iveljay said:
Three questions a) This is full frame, uncropped ?
b) What was the background - grass assorted leaves etc?
c) You didn't have any auto HDR or other enhancing feature switched on?

It looks vaguely similar to the problem you had with skies back in Feb 2012 but with different colours.

If the sample is cropped (but unprocessed) image from a full frame it would be useful to see the full frame.

My theory is that the contrast difference between the correctly exposed foreground and the underexposed background means that the background is way off the comfort zone of your cameras sensor/processing engine.
Under these conditions you get noise. I have just shot a book cover as an unerexposed background replicating your conditions and got some lovely chromatic orange brown noise on a nominally green area that is very close to your example. ISO 160 on Pana G5 which was the nearest camera at the time.

It will be worse with ring flash as there is great contrast difference between your subject and the distant background.

If the sample is full frame it would be interesting to know what it was you were shooting and what your settings were to hopefully be able to replicate.

Corrective action depends a bit on the original image but can be a bit of a pig - once used an Oly E-620 with its 'shadow adjustment' switched on at the wrong time and had several pics that I actually reshot.
Click to expand...
 
And what are the other settings in camera for sharpening, noise reduction, etc? These things might be possible to see for some, but I am not able to put plugins for such things on this PC.

Niels
 
There is a program called Neat Image where you can isolate your backgrounds with the lasso tool and apply the Neat Image to soften and smooth out the pixels.
 
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