Am I looking in to this too much???

Phill
7th May 2012, 18:54
Can someone please help me,
Using a Canon 500D mainly using zoom, in raw format, is the blotchiness of the attached photo normal, it has been cropped.

(Sad) Phill

Andy
7th May 2012, 19:20
You probably are looking it too closely, depending upon how dramatic the crop was... examining any photo up close, almost on a pixel by pixel basis will reveal limitations of camera/lens.
Here I can see chroma noise (coloured specks) which is down to the camera's sensor, probably too densely packed trying to get a high pixel count into a tiny sensor, also ISO settings being high will make this more pronounced.... it's not really a fault with your camera.
Some purple fringing on the white, which is mainly down to the camera lens.

We have a sister site on photography
http://www.worldphotographyforum.com/

Best regards,
Andy

Mad Landsman
7th May 2012, 19:29
It looks like there is some Chromatic aberration present - When the colours focus at different points on the sensor.

What lens are you using? Is it a Canon lens? Has it had a knock? Have you tried using another lens?

or, Maybe the sensor is loose and not holding in the right plane - That has been a problem with some Canon EOS digital cameras.

Are you using full auto? If so try it on aperture priority and close the aperture a little with slower shutter.

Phill
8th May 2012, 18:00
Hi Mad &Andy
This normally happens when using full zoom on a basic Canon 75-300mm 1:4-5.6 lens, Of note I normally use auto when using the zoom lens, I also use raw and j-peg together, would this add to the problem, and best just to use Raw.
Have attached a snap of one of our job choppers, with a cropped section, showing the problem.
Cheers
Phill

Andy
8th May 2012, 18:50
Hi Mad &Andy
This normally happens when using full zoom on a basic Canon 75-300mm 1:4-5.6 lens, Of note I normally use auto when using the zoom lens, I also use raw and j-peg together, would this add to the problem, and best just to use Raw.
Have attached a snap of one of our job choppers, with a cropped section, showing the problem.
Cheers
Phill

Can I ascertain that the problem that concerns you is the magenta colour fringing (chromatic aberration) on high contrast edges?
This is largely down to the lens.... expensive lenses have special glass that rectifies the problem of 'CA'.
See here for more detail on 'CA'
http://en.wikipedia.org/wiki/Chromatic_aberration

A bit of fiddling in photoshop, such as desaturating the problem colour in the areas effected, can make the problem less eyecatching.

With a normal sized print the problem would not be that noticeable in the first place, but these days everyone is cropping and examining on a monitor at far greater detail than ever before... which shows up lens deficiencies such as this.

cheers,
Andy

Mad Landsman
8th May 2012, 19:19
Hi Mad &Andy
This normally happens when using full zoom on a basic Canon 75-300mm 1:4-5.6 lens, Of note I normally use auto when using the zoom lens, I also use raw and j-peg together, would this add to the problem, and best just to use Raw.
Have attached a snap of one of our job choppers, with a cropped section, showing the problem.
Cheers
Phill

I have just put a Canon 75-300 mm Mk1 on my EOS 50D and took a photo out of the window.
I then mounted a Canon 18-135mm EFS IS and took the same shot.
Using RAW images I then cropped to the same part of the image, at the point of focus.

The then identical image from the newer digital dedicated lens is much better with less chromatic aberration even though the focal length is shorter.

So the answer, as Andy says, is in the lens.

Thanks to your question I now know that I might have a problem if I use the old lens on a digital camera - I last use that lens when I had an EOS 5D, which has a full frame sensor.

Phill
8th May 2012, 19:20
Mind at Ease

Cheers Andy:sweat:

Phill

Phill
6th October 2012, 16:48
Touch wood I’ve finally sorted it, the blotches were getting stronger, so I decided to send the camera back to Canon, luckily it only needed a sensor clean, with no charge, and now seems as good as new.
Is cleaning sensors an easy thing to do, or better to get it done professional the next time?.
Canon Eos 500d

Phill

Pompeyfan
7th October 2012, 11:03
Hi Phill

If it happens again, I would get it done professionally. I take mine to a local camera shop having had blotches in the past. You can do it yourself, my Canon handbook explains how, but it has never worked, so I take it to a professional. They charge 40, but worth it because the sensor is a very delicate component, as advised in the handbook.

peteloud
16th October 2012, 20:09
Sensor cleaning is very easy, you just have to be careful and sensible.

I follow the instructions in the back of my Sony A850 manual, (more or less). I use a blower then very lightly brush the sensor with a very fine and very clean lens brush.

It takes 2-3 minutes and gets rid of the fuzzy spots I sometimes see in the sky.