What's this on my bokeh?

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_MikeyB

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Michael
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I was playing around with some out of focus shots yesterday at a wedding with my new Sigma 1.4 35mm (Art) lens and I've noticed some really strange dots on my image...

Now I haven't had chance to test a different lens yet, but I'm suspecting this is from the lens and not the camera?

What do you think?

I'll do some testing later as I've another wedding on.

P.S My in-focus shots don't have any marks on them, which makes me think it might be on one of the aperture blades?

View attachment 18466

Here's a 100% crop

View attachment 18465
 
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Try another lens first to make sure it's not the sensor.
 
dont think it would be on the blades as it wouldnt show up in the images themselves as the bokeh is light refracting through the aperture of the blades and these marks are clearly on the aperture itself which points to specs on the glass or sensor.
Have you tried shooting a long exposure shot on plain white ( or mid grey ) with aperture set to around f/22 shoot a 2 second exposure on a clean white surface ( even move the camera a little to get more blur ) then open the image in your usual editing and see if they still appear.
looking closely the marks appear on quite a number of them so would check both lens and sensor.
 
I'll do both of your suggestions later today, thanks for the input. :)
 
They're not on the sensor - the pattern repeats. They must be from the lens.
 
That's what I thought DROJ.

I'll do some thorough testing later this week and keep you posted for those that are interested. :)
 
If those are glass light globes, could it not be the same globe with dust inside repeating?
Are they on any other images with a different light source?
 
Certainly less pronounced on the more recent shots but definitely present again on the 35mm
 
could be a very small amount of fungus as dust spots tend to move around a little even on a lens. these seem to be in exact same place. they look almost like water stains.
just did a google on effect of fungus on bokeh and the couple of images i found look almost identical.
how old is the lens?
whatever the cause dust or fungus it looks like it will def need a professional clean.
can you take a shot of a plain light grey or white background to see if/how it appears as it may be then easier to spot
 
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It's a new lens Dean as stated in first post.

I would be suprised if it's Fungus in a new lens, but you never know. Most new lenses I have bought have been sealed and they also contain silica gel to remove / absorb any moisture, which stops fungus growing. As this lens is in demand you would think there would be a quick turnaround with this lens and not sitting on the shelf for any period of time to allow fungus to form. I have had a few older lenses with fungus, but more advanced. If this is the case, they look like spiders webs or crazing effect, I had a old teleconverter delivered last week which had fungus in a middle element. To check if it's the start of fungus, take lens into a dark room and use a torch to check the elements, if it is the start of fungus you should see white spores.

I would go with water /oil stains.

Anyway, as the lens is new can't you just return for an exchange with supplying dealer.
 
I've emailed the supplier a link to this thread for their advice - I may just take my body and lens into them this weekend to have a butchers.
 
I'll have a test tonight. Spoke to the suppliers today and they asked me to test it without a filter on the front too - so I'll give that a whirl too.
 
Tried the lens without the filter on and it's exactly the same. Have noticed my sensor is filthy though - could that be the source of the problem even though other lenses bokeh is fine.

No matter what lens I use and point to the sky the same dots appear which is obviously the sensor - but only with the Sigma 35mm I get the strange dots on the bokeh....???
 
Dirty sensor will show (esp at smaller apertures) regardless of the lens - as expected. Might not show at f1.4 though.

The blob pattern visible on the 35mm is not likely to be down to the dirty sensor as the pattern is getting repeated over and over again in each circle.

Can you see anything when you detatch the lens and look through it towards a window for example ?
 
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Well I feel like a relieved idiot updating you on the lens but I've cured the problem.

Took the lens off the camera to have a look through the glass like dinners suggested and I could see 3 water marks on the inner element (the one closest to the camera when attached).

So I gave it a quick clean and everything is working perfectly!

The water must have got onto the lens when I shot a wedding in the rain the other day - either that or I've not cleaned it properly before and left the water marks on there...
 
It's good to know, and probably a relief to you! It's a bu**er when people don't let you know the cause.
 
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