Purple haze in lens

[poider]

G'day, I have a Nikon D7200 and today was using my Nikkor 50mm AF 1.8 D, I was outside taking photos of under my pergola, So I was standing out in the (sometimes sunny and sometimes cloudy ) taking photos of the shaded parts under the pergola, I was in Aperture priority mode and when I bumped it up to f/22 I got a purple haze in the centre of my photos, f/8 and f/1.8 were all fine and now I have tested the lens inside and do not have a problem.
Is this something I should be worried about?, is it common shooting from light to dark?
Peter

[ameerat42]

Could you possibly be talking about some aberrant WB (White Balance) behaviour in your camera.
Perhaps it was set to Auto WB or so and got fooled by some changing conditions. It's only a wild
guess, going on your description, as I'd hate to put it down to your having discovered a Yeti:eek:

Anyway, what about a pic or two of the phenomenon (or Yeti :D)

[poider]

Taken at f/1.8
136170
taken at f/22
136171
I tried many different ISO and aperture combos but the f/22 always gave the haze, but only when I shot back into the dimmer area under the Pergola.

[paulheath]

cant see any images

[ameerat42]

Poider. The attachments did not work.
Have a look at this page. (http://www.ausphotography.net.au/forum/showthread.php?156515-Attaching-Images-To-Posts-On-AP)

Just a stab, but I suspect that the underexposed part of the image is throwing a colour wobbly, possibly because
the brighter part of the image is dominating the WB. Anyway, enough speculation till I see the images.

[fillum]

Possibly flare?
Was the lens in sunlight when shooting into the pergola? Did you have a lens hood attached?

[Tannin]

Flare was my first thought, Fillum, but in general flare is worst wide-open and reduces as you stop down.

[jim]

Need to see the pictures obviously, but is the extra DOF at f22 picking up something on or in the lens?

[ricktas]

Do you have a filter on this lens? Perhaps someone told you you needed a UV filter to 'protect' the lens?

[poider]

This is at f/1.8
136180
and this is at f/22
136181

- - - Updated - - -

The images are there if you click on the Attachment, I did these the same as I always have but for some reason they dont work like normal as for the guide... I do not have a paperclip icon?

[ricktas]

This is at f/1.8
136180
and this is at f/22
136181

- - - Updated - - -

The images are there if you click on the Attachment, I did these the same as I always have but for some reason they dont work like normal as for the guide... I do not have a paperclip icon?

Use the 'go advanced' button at the bottom of the post screen, once you do that you will have the paperclip icon.

Interestingly, last night I could see the above attachments, now it is saying they are invalid.

I will also ask again, do you have a filter screwed onto the front of this lens?

[poider]

I will also ask again, do you have a filter screwed onto the front of this lens?

Sorry, no I don't have filters on any of my lenses
This is @ f/1.8
136192

This is @ f/22
136193
and thank you for your patience, technology and I do not get along well at times
Peter

[ameerat42]

To me it looks like either one of (or could it be a bit of both?):
1) a la Jim: something on the lens surface that's affecting the light transmission at small apertures*;
2) something causing reflections that manifest in the centre of the lens in the same conditions.

*The only trouble with this is that you'd usually get a loss of light transmission.

A couple of Qs:
1) Can you pick anything up with a good eyeballing :crzy: of the lens wide open?
2) Does anything appear if you (can) manually stop down with the lens?

- - - Updated - - -

PS: I tend to think it's something like point 2 problem above. :umm:

[arthurking83]

That's not flare.
While flare can be more obvious when stopping down, it's usually a small concentrated spot or series of spots.

Most likely a lens coating issue or something.

What model 50/1.8? How old, did you get it new .. etc.

Quick look at the f/22 image, my guesstimate is that there is an issue with the coating on the rearmost lens element on the lens(the rearmost being the lens between front of lens and camera).
Probably a coating wearing out or something.

Obviously not knowing the age/condition of the lens, that's just a guess.

Can you take a photo of the rear of the lens(obviously with another lens) with the affected lens set to infinity focus.
I don't have a 50/1.8 AF-D lens, but most, if not all lenses of that focus mechanism type, will have the rear element furthest to the rear of the lens when set to infinity.
That is, if you focus to closest focus distance(MFD), the rear element will be set to be inside the lens. An image of the lens set in this way will make it harder to assess.

Don't need an especially close up image, just a nice clear image of any rub marks, or wearing out of the rear lens element.

Just some curiously inexplicable points of note in the image.
The sun seems to be behind your position in those images.
That is, it looks cloudy, but there's usually still tell tale signs of the suns actual location.
There are just barely visible shadows from the legs of the outdoor seat on the ground, pointing towards the house .. which implies light source behind the lens.
More specifically, over your left shoulder ... as the shadows seem to be oriented to the top right of the image.
With the light source behind the lens, flare shouldn't be an issue.
Yet the lens seems to have flare/low contrast issues at f/1.8 too.
I've got a lens with a ton of dust in it. Lenses with dust in them will produce low contrast when the light source is in front of the lens.
Never seen it when the light is behind tho.

So, can you confirm if there is any outside light(like a floodlight) possibly facing the lens?
Or is there a window, not in the image, that could possibly reflect a lot of light back into the lens?

Fungus can also be an issue, but again would need an image of the lens.
Fungus in lens usually looks like super fine stringy textured, almost spiderweb like growth on a lens element.
So a point to keep in mind .. if it is fungus it would be a good idea to keep this lens away from all other camera related bits and accessories.

Another thing to do is to take a shot from under the verandah, looking to the back yard to compare the differences.

[poider]

I have had a good look at the surface of front and back open and stopped etc, I think I can rule our fungus, There does seem to be a purple reflective coating that seems to reflect a purplish light back from a yellowish light, The sun was to my left but blocked by clouds from where i was standing and the house blocked the light where the chair is.
There is a flood light sort of facing in the vague direction i was standing but it was not on, I Thank you all for your suggestions and help, I am pretty sure now that it is the coating on the lens reflecting some side light perhaps what was left of the sun on the day, i will check again on the weekend and let you all know.
The lens was purchased new from Teds and has been used very little. I have never had a problem with it before this and probably wont again.

[arthurking83]

...
The lens was purchased new from Teds and has been used very little. I have never had a problem with it before this and probably wont again.

Info like this is what we needed.

New from Teds, I assume not that long ago too .. which bodes well for the condition of the lens.
Never had the problem before .. but you may well have it again.

So it seems with that info, it was just a case of some odd lens flare. Light coming in from one side .. not unheard of.
I'd say that it was just one of those situations where everything fell into place for the effect to show up.

Just as a test for your sake .. next time the sun is out, take a photo of the sky. Sky can be just plain blue, clouds .. whatever but as long as the sun is shining. Point camera to a position in the sky where the sun is ahead of, but not in the scene.
move your orientation a bit this way and that. You'll see it's easy to induce flare in nifty fifty lenses. Comes and goes, no real rhyme or reason to it .. other than it does .. and it also doesn't!

I'd say that if you ever see it again and it then becomes a bother, even a cheapie $1 ebay lens hood will help with controlling it. I wouldn't waste money on a Nikon lens hood .. especially off ebay!(more likely to be a fake).
I have a couple of ebay lens hoods for an 18-105. a little bit flimsier than the Nikon supplied hood(which got way too loose anyhow, so became useless) .. but at $2 a pop, I got a few and even if they break or get lost or whatever .. they're cheap as chips to replace.

[poider]

[QUOTE=arthurking83;1456101
So it seems with that info, it was just a case of some odd lens flare. Light coming in from one side .. not unheard of.
I'd say that it was just one of those situations where everything fell into place for the effect to show up.

[/QUOTE]

That's why I say I will probably never have it again as I probably won't be in the same situation with that lens.

Thank you I will try that on the weekend
Peter

[arthurking83]

On a side note, and totally unrelated to the topic of the thread.
While I was studying the image for telltale signs of what could have caused the issue, and other than a reflection of strong light back into the lens, I can't really see anything obvious in the image .. but!

But I noticed the illusion that is depth of field.

That is, depth of field isn't always a real thing, and can be .. for lack of a better term .. implied, or virtual.
In this image there is an implied, or virtual, depth of field in the reflection in the window. The timber retaining wall in the reflection is blurred in the f/1.8 image .. just as it may have been if it were an actual retaining wall and not a reflection of one.
But in the f/22 image, the retaining wall is rendered more sharply, even taking into account the additional grain from high ISO noise, you can clearly see better detail in the timber texture in the f/22 image.

As we commonly think of DoF, that it extends into the image .. that is from the point of nearest focus to a point approaching infinity.
But in this image the reflection is only a virtual one, or an illusion that the distance shown extends towards infinity from the front of the lens. The actual image of the reflection is of course a flat plane .. being the window.

[Mark L]

I haven't read everything here yet but simply ISO 25600 might be your problem here.
KISS

[arthurking83]

I haven't read everything here yet but simply ISO 25600 might be your problem here...

Possible, but pretty much unlikely.
That is, simply setting the camera to ISO25600 won't cause purple flaring in this manner .. otherwise the camera maker has a lot to answer for! ;)

Not knowing every single detail in the surrounding area in the scene, my guess is that there's a window somewhere on the LHS of the image, out of sight, reflecting strongly back into the lens!

[ameerat42]

Does


...I was in Aperture priority mode and when I bumped it up to f/22 I got a purple haze in the centre of my photos, f/8 and f/1.8 were all fine...
+

... ISO 25600 might be your problem here...
=

Possible, but pretty much unlikely.
That is, simply setting the camera to ISO25600 won't cause purple flaring in this manner .. otherwise the camera maker has a lot to answer for! ;)
...
?

That "possibly" might end up being "likely"!

Q: How many times do you have to look at a thread before it starts to gel?

f/22 in the case of the 50mm lens used here is a smallish aperture of ~2.27mm.

Our good friend "diffraction" might be at play here. The conditions were trying enough, and at f/22 with the ISO racing...!

Peter, maybe another experiment is called for. Try photographing a white sheet of paper to fill about 3/4 of the frame.
Do two runs: one in goodish sunlight, the other closer to your conditions for this lot, doing just what you did for these.

[poider]

I will do some more tests in the future, I am not well currently and will get back to it when I recover...Thank you all for your input and suggestions, I will keep it going when I can
Peter

[Hawthy]

I need to agree with Mark here. 5 pm. Mid-winter. Adelaide. Presumably dim light.

First photo: f/1.8 and ISO 250 gives a reasonable picture.
Second photo: f/22 and ISO 25,200 gives a purple haze.

Going from wide open aperture to almost closed is really pushing the boundaries.

I don't think that anyone can reasonably expect a DSLR to produce similar results in dim light when the ISO varies so greatly.

[arthurking83]

I need to agree with Mark here. 5 pm. Mid-winter. Adelaide. Presumably dim light.

First photo: f/1.8 and ISO 250 gives a reasonable picture.
Second photo: f/22 and ISO 25,200 gives a purple haze.

Going from wide open aperture to almost closed is really pushing the boundaries.

I don't think that anyone can reasonably expect a DSLR to produce similar results in dim light when the ISO varies so greatly.

Would probably pay to be a bit more critical of the image tho.
image one at ISO250 whilst 'reasonable' is badly affected by flare/haze. The grey-ish periphery of the image, mainly LHS, lower edge and RHS(probably worst affected) are the cues to that assessment.

50/1.8 lenses are, in general, quite prone to flare/haziness/low contrast/etc in marginal situations such as contra light. Some nifty fifties are better than others, but I know Nikon's 50/1.8's are one of those that are.

Closing the aperture down helps with increasing contrast rendering in some cases, but when there is still contra light present in the scene, the smaller aperture can also serve to concentrate the low contrast/flare spot.

With respect to the underlined section of the reply:
One of the main points in choosing a DSLR is their ability to maintain quality in the image at elevated ISO levels without compromising image quality too much.
If the ISO value chosen in the second image was the cause of the purple haze affliction, then it's reasonable to assume that the purple haze would propagate at the periphery of the image, as in the the low contrast rendering in the f/1.8 image, and not move from the periphery to the centre of the image as it has done.

The ISO value, in isolation, can't be the cause of the purple haze. If it were, then as I said earlier, the manufacturer has a lot to answer for. Simply upping ISO and that setting producing purple haze spots in an image is unacceptable.
I have thousands of image shot at ISO52K which don't have haze spots in them, and the world of photography has literally billions of image available for viewing that show images at ISO25K with no haze effects.

The cause of the purple haze spot is the f/22 aperture used(which concentrated the flare into the centre of the image).
and what I think must be a strong reflective light source(ie. contra light) coming back at the lens which caused the low contrast areas in the f/1.8 image, and subsequently the haze spot in the f/22 image.

The simple act of upping ISO to reasonably high values doesn't cause flare spots. Can highlight them in some situations, but doesn't cause the phenomenon.