Can someone share some insight on this problem ?

[harlequin2902]

Can someone share some insight on this problem ?

(Note : The images included for illustration are all full frame re-sized shots)

I think some of you know that I had some problems with my current lens when I first got it (used). One of the internal elements had a weird stain that affected every picture that I took, giving them a grossly misty and soft look :

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Then I took it down to Cathay Photo's warehouse for it to be serviced. The technician said that the stain was caused by the breaking down of the coating on that particular element. He went on to clean it for me and removed the stain. After that, all my shots looked more normal.

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However, I then realized that whenever I tried to shoot something against a bright blue sky, the image would end up having an overall bluish tinge.

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[harlequin2902]

CONTINUED...

And if I shot something against an overall bright background, a wee bit of the old problem (misty, soft look) would come back to haunt me. But note that this happens only when the background is very bright. These 2 images were captured on the same day at the same location. The first was captured when the sun was shining directly down on the pond, while the second was taken when the sun went behind the clouds a little.

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What do you think is the reason for this weird lens behaviour ? Is it really caused by the lens element with the now (presumably) absent coating after the "...remnants of the old degraded original coating was cleaned off..." ? :thinking:

[Mervin]

think it is the "washed/cleaned" out coatings. :dunno:

should the effected element be replaced ???

[joeyao]

I think your lens suffer from what is known as flare. Maybe this review may help you to understand your lens' flaw:

http://www.photo.net/equipment/canon/70-300do_2/

Go to the part on "flare".

[harlequin2902]

I think your lens suffer from what is known as flare. Maybe this review may help you to understand your lens' flaw:

http://www.photo.net/equipment/canon/70-300do_2/

Go to the part on "flare".Thanks for the link Joe :thumb: And like what was mentioned in the review, I sometimes use the auto-levelling / contrast adjustment feature on PS to 'retrieve' the lost contrast due to this 'flaring'.

But is there any way to reduce it while I'm out in the field ? A larger/longer lens hood perhaps ? :thinking:

[joeyao]

But is there any way to reduce it while I'm out in the field ? A larger/longer lens hood perhaps ? :thinking:No harm giving it a try. I presume if you can find a longer lens hood to attach to your lens.

[Garion]

Thanks for the link Joe :thumb: And like what was mentioned in the review, I sometimes use the auto-levelling / contrast adjustment feature on PS to 'retrieve' the lost contrast due to this 'flaring'.

But is there any way to reduce it while I'm out in the field ? A larger/longer lens hood perhaps ? :thinking:I would advise not to use "auto-contrast" or "auto-levels" in PS. Best to adjust contrast/levels manually yourself using the slide rulers.

I believe the lens flare is due to Sam pointing his lens directly at the water reflections, in most cases the manufacturer hood is enough to prevent flare unless in certain situations like this one. The bluish cast, however, might be due to a faulty/misfunctioning lens element, hence recommended to send it in for replacement of the affected part.

[eric]

I think your lens suffer from what is known as flare. Maybe this review may help you to understand your lens' flaw:

http://www.photo.net/equipment/canon/70-300do_2/

Go to the part on "flare".

Ya... it should be due to flare, remember we were taking almost against the sunlight at 10'o clock our direction, the sun rays can easily come in at such angle...

[sulhan]

Hi Guys...

Looks like the lens grease condensation.....is the problem. My Sigma len recently went to Sigma for this problem....

Its is known for sigma lens to have this behavior especially if the lens is used alot in hot weather. This is a known problem since my first 70-300 APO Macro super.

And now the problem occured on the Sigma 70-200 EX APO.

The failure mode is fine condensation dots well visible throught the back of lens onto a bright light source.....

rgds,
sulhan

[harlequin2902]

Hi Guys...

Looks like the lens grease condensation.....is the problem. My Sigma len recently went to Sigma for this problem....

Its is known for sigma lens to have this behavior especially if the lens is used alot in hot weather. This is a known problem since my first 70-300 APO Macro super.

And now the problem occured on the Sigma 70-200 EX APO.

The failure mode is fine condensation dots well visible throught the back of lens onto a bright light source.....

rgds,
sulhanHmm, so I take it to mean that this will be a recurring problem ?

That means it's nothing to do with some "damaged/worn out lens coating" like the technician suggested then ? :thinking:

[sulhan]

Hmm, so I take it to mean that this will be a recurring problem ?

That means it's nothing to do with some "damaged/worn out lens coating" like the technician suggested then ? :thinking:

Hiee...Harl..

Lens coating degradation and the condensation problem can be physically distinguished differently....per my past experience and from old birds......

Some coating degradation may be due to fungus override and digs into the coating and once clean gives an obvious colour tinge difference to the good surface next to it.... and those with grease condensation....will normally have little minute dots like spores almost evenly spaced on the element/s .....

I have one lens given to me for free by one of the fellow photographer ....with a badly damages coating due to history of fungus....
Already been cleaned though but the raibowish tinge looks really bad.

Guess what, i actually took the lens apart and "totally remove" that particular coating...by using lens cleaning solution and now the lens looks a good as new (less that coating). Its now my main macro combo that gives sharp and great images even without the coating.....

The coating is crucial for landscape shots where the multi elements anti-reflection is critical to avoid flaring. So this lens, though not as good as new in landscape shoot performance but is a great lens for macro where the lighting is controlled.....no bright sunlight...


rgds,
sulhan