Glare ? Dust ? Sensor Problem ?

[rajatsingh78]

Following is the series of shots taken while increasing the f-stop (reducing the aperture), lens used is Nikkor 50mm 1:1.8D (camera body is Nikon D90)

I was inside the room and this DTH dish was on the other side on a different building, the sun was right above the DTH dish

So it seems this patch (which is actually a heptagonal) comes in the pictures when I increase the f-stop (decrease the aperture) you can see it in the series of pics right where the DTH dish is.

I have another Nikkor 28-80mm 1:3.3-5.6G lens with which I was able to replicate the patch not so consistently (made sure that the zoom was at 50mm),

I am quite sure that there is nothing wrong with the camera, but curious on why this patch is coming, is there a possibility that there is something wrong with the prime lens, if not how to make sure that this doesn't come in case I am shooting in strong sun with max f-stop (min aperture)

I have edited the pic by increasing the contrast to make the spot more visible

 

[tirediron]

Hard to say with such small images, but it rather looks like a case (albeit an extreme one) of purple fringing.

 

[clanthar]

Lens flare and chromatic aberration. These occur when you shoot a subject with extreme high contrast edges (dark/light) and when you shoot into a light source.

Smaller camera sensors exacerbate the problem and otherwise lens design and lens coatings help control the problem. Always use a lens shade to help suppress flare. No camera/lens combination will ultimately be flare and CA free -- the cost/effectiveness curve to get better hardware that does a better job looks a lot like the increase in housing prices in the years leading up to 2008.

Joe

 

[rajatsingh78]

Thanks for the explanation, do the lens flare/chromatic aberration have a heptagon shape, this one at times shows up as a heptagon (Heptagon - Wikipedia, the free encyclopedia)

Will you count the D90's sensor as small or you meant that only full frame camera won't have this problem?

BTW I am still a learner, started with a Nikon F55 Film SLR + Sony W55 P&S, recently moved to a Nikon D90, this issue is more prominent with my 50mm prime lens 1.8D

Lens flare and chromatic aberration. These occur when you shoot a subject with extreme high contrast edges (dark/light) and when you shoot into a light source.

Smaller camera sensors exacerbate the problem and otherwise lens design and lens coatings help control the problem. Always use a lens shade to help suppress flare. No camera/lens combination will ultimately be flare and CA free -- the cost/effectiveness curve to get better hardware that does a better job looks a lot like the increase in housing prices in the years leading up to 2008.

Joe

 

[clanthar]

The shape is a reflection of the shape of the iris inside the lens -- that's classic flare -- you see a heptagon because your lens iris has seven blades. The purple/blue color is classic CA.

The D90's sensor is small but small is relative. The D90's sensor is big compared to most compact cameras. A camera with a 35mm equivalent full frame sensor has a small sensor compared with a Hasselblad H-4D. The larger the sensor the better control over CA, but it's not gone. The problem persists with larger sensor cameras; it gets progressively less severe as the sensor size increases. And as I said the cost/effectiveness curve is steep -- that H-4d costs $30,000.00; get one tomorrow and your problem will almost go away.

Flare and CA are a fact of life that we all live with. The quality of our hardware is a factor, but we all have to live reasonably within our means.

Different lenses do perform better/worse than others relative to flare and CA. If you have a particular lens that you notice causing more trouble than others then you can consider at some point replacing that optic.

Joe

 

[rajatsingh78]

Thanks Clanthar for the response and explanation,

I did a second test today indoors with indoor lighting, again a white spot appeared in the shot that I took with the Nikkor 50mm 1.8D at f22, I tried to replicate the same with my Nikkor 28-80mm at same f-stop and same shutter speed of the same subject (a blank wall) and I was not able to replicate the spot.

following is the shot that I took indoor,
http://i86.photobucket.com/albums/k99/rajatsingh78/DSC_3758.jpg
and this one again outdoor
http://i86.photobucket.com/albums/k99/rajatsingh78/DSC_3661.jpg

If this is the case then practically this prime lens is completely unusable at higher f-stops ?

Is this a known drawback for this particular prime lens?

The shape is a reflection of the shape of the iris inside the lens -- that's classic flare -- you see a heptagon because your lens iris has seven blades. The purple/blue color is classic CA.

Flare and CA are a fact of life that we all live with. The quality of our hardware is a factor, but we all have to live reasonably within our means.

Different lenses do perform better/worse than others relative to flare and CA. If you have a particular lens that you notice causing more trouble than others then you can consider at some point replacing that optic.

Joe

 

[clanthar]

Woah! -- these new photos provide additional information. I would now say you have a flawed lens; something is wrong that's causing this ghost image of the aperture in the center of the frame. I'd still use the word flare but it's not right for a lens to flare under these lighting conditions.

Joe

 

[rajatsingh78]

Hello Clanthar, a recent development in my issue, I got hold of a Nikon D5000 and another 50mm lens, both the lens (mine and the other one) created this patch on my camera. However my lens didnot create this patch on the D5000..phew what a huge confusion

 

[clanthar]

I'd say you've narrowed it down to your camera body with this test, but there's the additional factor of your 28-80 not causing the problem on your camera body. So the data you have is still conflicting. It doesn't make sense that the 28-80 would not cause the problem.

Joe

 

[UUilliam]

Have you ever tried to clean your sensor with liquid solutions?
it me be remains of the solution (lens cleaner on sensor?) on the sensor.

Try another lens on it see if it does the same?

 

[rajatsingh78]

Have you ever tried to clean your sensor with liquid solutions?
it me be remains of the solution (lens cleaner on sensor?) on the sensor.

Try another lens on it see if it does the same?

Nopes...its a 4 month old body, no cleaning done so far.

 

[rajatsingh78]

Some updates, did another test today

The only editing that I did in this photos was reduce amount & saturation to -100 (used Microsoft Office's default photo editor)

and then

 

[UUilliam]

Looks like it is a problem with your 50mm lens.

I suggest taking it back or asking someone else to test it to see if it happens wit them too.
unfortuanetly that is the best advice I can give you.
and it seems you had already drawn that conclusion in the initial post.