p.1 #1 · Dust in a Contax 85mm F1.4, is it hard to remove?
Just bought a lens on Ebay and I noticed that from F10 to F16 I get a little black dot on the pictures and I can clearly see the dust between the front elements with my eyes when I look true the lens.
So to my question, is it hard to clean this by myself?
I have no experience at all with taking apart a lens.
p.1 #5 · Dust in a Contax 85mm F1.4, is it hard to remove?
thrice wrote:
Sorry but you're wrong, there is NO WAY diffraction isn't obliterating that dust spec regardless of aperture, unless it's the size of an M&M.
According to my experience with dusty lenses (zooms particularly), there is definitely a way.
p.1 #6 · Dust in a Contax 85mm F1.4, is it hard to remove?
Mmhmm, show me the lens and the sample shot. The laws of optics simply don't support the idea of individual dust particles inside or on a lens surface showing up in the image.
If you put a thick layer of dust that obscured say 30% of one of the lens surfaces inside or on the lens you might see a veiling glare and lack of contrast.
p.1 #8 · Dust in a Contax 85mm F1.4, is it hard to remove?
Yes, dust in almost any lens over about 35mm will show up as solid black specs in bokeh highlights at apertures under f/22 or so - even relatively small specs. And the longer the lens the less the aperture is relevant. In fact a great way to tell if dust is significant enough to affect IQ is to go out at night with the aperture opened up, focus it to the lens's MFD and then shoot some distant street lights. If you see specs you can't say that the dust won't affect IQ. In such a case it will both lower the contrast in some areas when normally shooting and also show up as hard black specs in the bokeh highlights.
I dunno if that's what MRosth is seeing but it's certainly possible.
p.1 #12 · Dust in a Contax 85mm F1.4, is it hard to remove?
AmbientMike wrote:
Im getting weird stuff in center, m4/3. 90 Tamron 49B gives white dot 135/3.5 zuiko gives purplish dot sometimes. Past f8. Both clean I think.
That sounds like an aperture spot from internal reflections. You'll probably only see it in bright conditions.
p.1 #18 · Dust in a Contax 85mm F1.4, is it hard to remove?
In my experience particles and smudge on the back/rear element of a lens can be visible but even major particles are practically invisible if they are on the front element, exceptions are water drops and smear etc.
I have seen a telephoto lens with a crack in the front element where the chipped part had been painted with a black felt pen and nothing was showing up in photos. The owner said it was standard practice in sports photography.
p.1 #19 · Dust in a Contax 85mm F1.4, is it hard to remove?
MRosth wrote:
There are still some small dirt/dust dots but not as big as seen on the first picture
With a quick look I see 3 remaining spots which to me look as typical sensor-dirt. Buy a 10€ blower and they are likely to disappear, should have nothing to do with the lens.
Never seen anything like the first one, except for when I had dirt on the matte screen. But that would only concern the OVF, not the image.
p.1 #20 · Dust in a Contax 85mm F1.4, is it hard to remove?
MRosth wrote:
That was my first thought as well but it doesn't show up on any of my other lenses.
Did you test those other lenses fully stopped down, too? I agree with wfrank, all of this looks like sensor dust to me, and maybe by coincidence that big blob fell off (anti dust vibration) while you had the lens repaired.
