Weird blobs in my bokeh

[davidc]

I've brought this question up with the photo club at work and I've received many different opinions as to what it is, wanted to run it past you guys too.

I noticed it while editing last night's 365 image. I've attached a crop of the area in question. As you can see, each diffuse light orb in the image bokeh has ... "imperfections" in them. I'm not sure what this is but it's 99% likely to be

1) a problem with the lens
2) a problem with the sensor

Since this doesn't happen on any other bokeh with a different lens that I can remember I'm concluding it's the lens, although I'll be doing a dust-check shot and testing other lenses again tonight to be sure.

Which leaves the lens, probably. Is it dirt? Fungus? Maybe a tiny bubble in the glass?

bokeh.jpg

(509.86 KiB) Not downloaded yet

[Mike Farley]

Hi David

It's difficult to know exactly what is causing this, although I would add a third reason to your list of possible culprits - combination of lens and sensor. Many lenses were designed for film with the elements set up so that the red, green and blue light (each of which has a different wavelength) hit the different layers on the film. Also, most sensors require the light to hit it at a 90 degree angle, but with some lenses - wide angles in particular - the light comes in at a sharper angle, especially the edges. For digital, telecentic designs work best and this is standard for 4/3 and m4/3 which are digital only formats. Whether any of this would account for the bokeh you are seeing, I am not sure. Have you tried googling to see if the lens you are using has been noted by others as having this characteristic?

[davidc]

Well it's certainly not the best built or most expensive lens and I did get it 2nd hand from ebay so I can't expect perfection. However I did notice some dust spots on it when testing with a torch so I think I've cleaned those off now and will retest again soon.