Any idea on what is causing this??

rpo83

Member
I have just returned from taking a few images with my new camera.

Camera is a SD14 with Leica mount, i was using an Elmarit 28mm f2.8 lens/

I am seeing a major problem, at first i thought it was simply lens flare, as i was shooting towards the sun, so i turned 180 degrees and took more images, on some shots the same issue is visible, does anyone have any suggestions? I understand that the sun reflecting off the rocks may have cased it, but i can't figure out how or why it has occurred with the tree reflecting in the pond shot!

Here are a couple of images:



SDIM0081a.jpg

SDIM0063a.jpg

Any help would be appreciated.

Cheers

Steve
 

Steaphany

Well-Known Member
The Magenta region in the center of the image is reminiscent of the behaviour of the SD14 when the Dust Protector/IR blocking hot mirror is removed for broad spectrum or IR photography. In this mode, the phenomenon is uniform across the whole image and is characterized by the strong adjacent signal on the Red photodiodes causing a suppression of the Green signal.

Steve, with your camera, does this happen on every image ?

Have you tried shooting a uniformly white surface to see if this manifests under controlled conditions ? (Note that the Autofocus will not lock on a contrast less uniformly white field, set focus to manual.)

Many people here have shot photos where the Sun was near or within the field of view, including myself, and no one else has mentioned experiencing a center Magenta hot spot.

I've noticed that the EXIF data was lacking in the files that you loaded into your post, so what were your camera settings ?

Do you have a second lens to see if this is an issue with the lens used or a common issue with the SD14 ?
 

rpo83

Member
Hi Steaphany,

Thanks for the reply, i am using one of Luis' dedicated Leica R mounts, with a Elmarit 28mm lens. Hence no EXIF as manual settings only. The waterfall shot was approx 1.5 second exposure at 50iso f16.

I have emailed Luis and i am waiting for his reply. He has the lens listed as a fully compatible lens, but the information was passed on to him by a 3rd party. Luis is concerned that the lens light sheild may be touching the filter, as the lens does not lock into position properly. I have carefully checked for any visible signs of this, but it all looks OK. So maybe this is evidence of the filter being physically distorted by the lens :eek:

It is not on all shots, but i took about 70 shots today and i would say it was on at least 50 of them.

Here is a screen capture from SPP. Sorry about the size of the image, but i wanted to keep it as large as possible so you could see the problems.

Cheers

Steve

 

Steaphany

Well-Known Member
I feel you may be onto the mechanism with:
evidence of the filter being physically distorted by the lens :eek:
If you look at my thread:

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the image described as Color Corrected demonstrates a central IR bias fading to a normal color rendition at the periphery of the image as the angle of light through an external Tiffen Hot Mirror varies.

If the lens is in contact with any part of the SD14's Dust Protector/Hot Mirror, either the filter itself or the frame, any distortion could alter the angle of light and cause the effect your seeing.

FYI, I broke my Dust Protector/Hot Mirror, see the thread
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, so be warned that it can not take much stress.
 

rpo83

Member
Hi Steaphany,

I have just removed the filter and refitted the lens, it didn't help with the mounting issue, so i am very confident that the lens is not touching the filter.

I have just sent Luis the RAW file so he can have a look.

My other Leica lenses should arrive next week, so hopefully i can draw some more conclusions when i attach a different lens. The fact that a few photo's are OK is somewhat confusing though!

Cheers

Steve
 

rpo83

Member
Here is a link to the X3F file of the tree, if anyone would like to have a closer look:

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The link should work, i have set it for open public access.

Cheers

Steve
 

tc95

Well-Known Member
Steve,

Take a high power flashlight....and shine it thru the lens with the aperture wide open...check to see if you have fungal growth or cleaning marks....inside the lens... this really should not affect the image....but maybe something is causing the sensor to capture a different light image when the lens is on...

I have the Nikon F conversion I have not had this issue with my sigma....but one of my MF nikon lenses with a nikon camera produced this not in the center but around the outside....it was a 50mm f1.4 E lens....it had fungal growth on the outside....ebay lens...I took the lens apart and cleaned it the fungus left tracks in the lens...but other than that the pictures started to come out better...

Maybe this will help maybe not....the other thing you can try going back to what Steaphany said about the IR hotspots..try taking shots at higher f-stops....if it goes away..then you have a hotspot issue...

Tony C.
 

rpo83

Member
Thanks Tony,

I don't believe it is a problem with the camera or Luis' mount, i am hoping it is the lens, but i must say it has me stumped!

There is no evidence of fungus, the elements are very clean, however it is an old lens, and who knows how it has been treated in the past.

I'll post any updates as soon as i discover anything.

Cheers

Steve
 

tc95

Well-Known Member
Steve,

You defiantly have a hot-spot....do you have a polarizer you can try with the lens to see if this corrects it.....??

It actually starts in the center and goes out like a triangle around the bottom of the picture...you can see it with my grossly blown out image I played with...

Hot-Spot.jpg


I am interested in seeing what Luis has to say....also look at this site....and post your concerns there too...he might check his site more often...

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I would be interested to hear what he says.....

Tony C. :z04_cowboy:
 

rpo83

Member
I have been talking to Luis this evening by email, unfortunately living half a world away creates time issues.

He has been wonderful, providing a wealth of ideas. He is just about to leave home now, so i will probably hear back from him tomorrow after he studies the X3F file. He certainly provides great customer service.

Cheers

Steve
 

rpo83

Member
Here is one of my first test images with the lens, much higher contrast than today, early morning light striking the leaf.



No evidence of the problem that i can see.

Cheers

Steve
 

rpo83

Member
I have been looking at what is similar in the images that display the problem.

I think i have narrowed it down to small apertures, in some of the boat house pics, i forgot to reset the aperture after i opened up the lens to focus, most of the problem shots would have been shot at f16 or f22. Does this shed any light on the problem?

Steve
 

tc95

Well-Known Member
Steve,

That would coniside with Steaphany and my statements above concerning the IR shots...when shooting IR you get hotspots with certain lenses...not all lenses do this...and even two copies of the same lens may or may not do this....

I don't know the technical reason why you get this...maybe something to do with how the lens bends the light to fit on the film or sensor produces this issue...(really have no need to technically know why...I just know it happens)...

When playing with my IR modified camera's when I get this I usually dial up the f-stop from 1.8 to like 4 then 6 or 8 and it usually gets rid of this issue...(again back to how the lens handles the light comming into it)...so I have played with my MF lenses and I keep a note book with each lenses pros to cons and what is needed to take sharp images with a particular camera.....(I am a little anal)....so when I grab a lens I quickly check my notes to re-familiarize myself with it...so I don't get any issues....

By the way...great shot above....

Tony C.
 

Steaphany

Well-Known Member
Section 4.7: Recognizing and Correcting Equipment Problems, Page 105, of "The Handbook of Astronomical Image Processing" by Richard Berry and James Burnell has a nice graphic explaining the origins of Hot Spots, Field Flooding, and Vignetting:

lens.jpg

If the rear structure of the lens body is providing the reflective surface causing the hot spot, the sharp angle away from the dust protector/hot mirror normal may be why this manifests as being spectrally dependant.
 

tc95

Well-Known Member
Steaphany is awesome...!!! :z02_respekt:


Thank you I actually wanted an answer to that question...tried looking one time but no-one could explain-it or show why it happens....

Tony C.:z04_cowboy:
 

Steaphany

Well-Known Member
BTW, my Sigma 28mm DG EX Aspherical Macro lens intermittently produces an IR hot spot dependant on exposure.

For some IR exposures, the image has a hot spot, at other settings there is none. I still have to run some specific tests to understand what's going on.

Understanding exposure dependant IR hot spots may explain why the same model lens used by different photographers yields IR images with and without hot spots.
 

rpo83

Member
Just an update for you all, Luis has spent some time looking at my images and believes it is stray light causing the issue. He recommended trying to keep the lenses at f5.6 - f8 to maintain maximum sharpness and faster shutter speed and minimise the chances of this problem happening again.

One of the things i want to start playing with, is night exposures, so Luis' recommendation of faster shutter speeds wasn't what i wanted to hear!

So with the 28mm mounted, i wandered down to a little church near me to shoot some high contrast night shots. this shot was taken at f8 and 10 seconds at iso 200, no hint of the problem :z04_breakdance.gif:

Here is the shot:

SDIM0139www.jpg


Cheers

Steve
 

tc95

Well-Known Member
Steve nice shot...what does it look like in B&W...??? sorry sorta on that kick lately..:z04_yes:

Tony C.
 

rpo83

Member
Hi Tony,

I hadn't thought about B&W, here it is...

SDIM0139-2.jpg

I don't mind that at all, i played with the curves a little bit, but have never done B&W before.

Cheers

Steve
 
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