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Circular Light Areas in Photo

 
 
Matt
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Posts: n/a
 
      07-01-2005
On Fri, 01 Jul 2005 15:22:23 -0400, Steven Feinstein
<(E-Mail Removed)> wrote:

>Scott W wrote:
>> Steven Feinstein wrote:
>>
>>>I have a Canon A95. Occassionally (and I'm trying to narrow down when)
>>>I take a photo and I get small circular areas which are lighter than the
>>>rest of the area. They remind me of what would happen when painting
>>>watercolors and an area blooms (but it is a perfect circle).
>>>
>>>It seems to happen when the flash fires but the subject is too far away
>>>or there are small areas of other sources of light. It also appears to
>>>be worse at 400 ISO.
>>>
>>>I'm trying to figure out what is happening in order to avoid the
>>>situation. If I had to make a guess, I'm thinking the shutter speed is
>>>fast (because the flash is firing), but the flash is not bouncing off a
>>>close object so the camera is picking up the light from the flash. Or
>>>if there is a window maybe it is picking up some outfoor light peaking in.
>>>
>>>Has anyone else seen this? Does what I suggest sound plausible?
>>>
>>>Looking for some advice on the cause.
>>>
>>>Thanks,
>>>
>>>Steve

>>
>>
>> It would help if we could see one of these photos.
>> You might try aiming the camera straight up on a clear night and taking
>> a flash photo.
>>
>> Scott
>>

>I uploaded three images as examples. Dust does seem to make sense, it's
>just that we took pictures at the same locations in a previous year
>using a point and shoot film camera and did not have this problem. Does
>it sound more like chance or is digital more sensitive to the dust?
>
>Light areas are:
>lapel of man
>knee of boy
>above white banner
>http://members.cox.net/sfein/images/img_1300.jpg
>
>Light areas are:
>at bottom
>on right near door
>http://members.cox.net/sfein/images/img_1258.jpg
>
>Light areas are all over the place:
>http://members.cox.net/sfein/images/img_1254.jpg
>
>I appreciate all the help from everyone.


Classic ORBS
http://homepage.ntlworld.com/h.cowell/orbs.htm

I don't agree with the paranormal suggestions, since I was able to
generate them on demand, by thumping a rather dusty chair and shooting
it with flash.

The classic digital ORB (always worse on digital) is caused by flash
illumination/backscatter from near field dust, the point being
defocused into a lightened circle.

Of course, they show up worse on black.
It also seems logical that they would be worse at high ISO, if the
alternative is a wider aperture.

They also seem to be common in church wedding photos - I guess it's
the number of people that raises dust, and that you tend to be working
at the outer end of flash range, so the flash is at maximum, and the
relative nearfield illumination is greater

There is no reason a film camera can't produce orb effects - a fixed
focus compact would be most likely to, but they just don't seem to be
as bad.

--
I may be dozzzy, but take the ZZZ's out to mail me
http://www.junkroom.freeserve.co.uk/jvc2080.htm - 2x2x24 CD-RW troubles

If you drop a cactus, don't try to catch it!
 
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Ron Hunter
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Posts: n/a
 
      07-01-2005
Steven Feinstein wrote:
> Scott W wrote:
>
>> Steven Feinstein wrote:
>>
>>> I have a Canon A95. Occassionally (and I'm trying to narrow down when)
>>> I take a photo and I get small circular areas which are lighter than the
>>> rest of the area. They remind me of what would happen when painting
>>> watercolors and an area blooms (but it is a perfect circle).
>>>
>>> It seems to happen when the flash fires but the subject is too far away
>>> or there are small areas of other sources of light. It also appears to
>>> be worse at 400 ISO.
>>>
>>> I'm trying to figure out what is happening in order to avoid the
>>> situation. If I had to make a guess, I'm thinking the shutter speed is
>>> fast (because the flash is firing), but the flash is not bouncing off a
>>> close object so the camera is picking up the light from the flash. Or
>>> if there is a window maybe it is picking up some outfoor light
>>> peaking in.
>>>
>>> Has anyone else seen this? Does what I suggest sound plausible?
>>>
>>> Looking for some advice on the cause.
>>>
>>> Thanks,
>>>
>>> Steve

>>
>>
>>
>> It would help if we could see one of these photos.
>> You might try aiming the camera straight up on a clear night and taking
>> a flash photo.
>>
>> Scott
>>

> I uploaded three images as examples. Dust does seem to make sense, it's
> just that we took pictures at the same locations in a previous year
> using a point and shoot film camera and did not have this problem. Does
> it sound more like chance or is digital more sensitive to the dust?
>
> Light areas are:
> lapel of man
> knee of boy
> above white banner
> http://members.cox.net/sfein/images/img_1300.jpg
>
> Light areas are:
> at bottom
> on right near door
> http://members.cox.net/sfein/images/img_1258.jpg
>
> Light areas are all over the place:
> http://members.cox.net/sfein/images/img_1254.jpg
>
> I appreciate all the help from everyone.


With the exception of the first picture, the flash should have been
turned off. Flash is useless beyond about 20 feet, and will only cause
the problem you are seeing, and will force the camera into a mode that
will probably result in a picture that is worse than it would be without
flash. In the first case, the problem is easily solved by just about
any photo editor. In the others, it is pretty much a lost cause.
Don't use the flash if the subject is beyond 20 feet, and don't use it
in dusty environments.


--
Ron Hunter http://www.velocityreviews.com/forums/(E-Mail Removed)
 
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Ron Hunter
Guest
Posts: n/a
 
      07-01-2005
Morton Linder wrote:
> Steven Feinstein wrote:
>
>> Scott W wrote:
>>
>>> Steven Feinstein wrote:
>>>
>>>> I have a Canon A95. Occassionally (and I'm trying to narrow down when)
>>>> I take a photo and I get small circular areas which are lighter than
>>>> the
>>>> rest of the area. They remind me of what would happen when painting
>>>> watercolors and an area blooms (but it is a perfect circle).
>>>>
>>>> It seems to happen when the flash fires but the subject is too far away
>>>> or there are small areas of other sources of light. It also appears to
>>>> be worse at 400 ISO.
>>>>
>>>> I'm trying to figure out what is happening in order to avoid the
>>>> situation. If I had to make a guess, I'm thinking the shutter speed is
>>>> fast (because the flash is firing), but the flash is not bouncing off a
>>>> close object so the camera is picking up the light from the flash. Or
>>>> if there is a window maybe it is picking up some outfoor light
>>>> peaking in.
>>>>
>>>> Has anyone else seen this? Does what I suggest sound plausible?
>>>>
>>>> Looking for some advice on the cause.
>>>>
>>>> Thanks,
>>>>
>>>> Steve
>>>
>>>
>>>
>>>
>>> It would help if we could see one of these photos.
>>> You might try aiming the camera straight up on a clear night and taking
>>> a flash photo.
>>>
>>> Scott
>>>

>> I uploaded three images as examples. Dust does seem to make sense,
>> it's just that we took pictures at the same locations in a previous
>> year using a point and shoot film camera and did not have this
>> problem. Does it sound more like chance or is digital more sensitive
>> to the dust?
>>
>> Light areas are:
>> lapel of man
>> knee of boy
>> above white banner
>> http://members.cox.net/sfein/images/img_1300.jpg
>>
>> Light areas are:
>> at bottom
>> on right near door
>> http://members.cox.net/sfein/images/img_1258.jpg
>>
>> Light areas are all over the place:
>> http://members.cox.net/sfein/images/img_1254.jpg
>>
>> I appreciate all the help from everyone.

>
> Hi,
>
> I noticed the same type of light circles, only with flash from a great
> distance where the pictures were grossly underexposed, and were
> presumably shot at ISO 400 (automatic) in my Canon S-500. I assumed that
> it was a kind of digital "noise", and can't imagine why ISO 400 shows up
> dust more than ISO 100.
>
> Morton


I believe you have the cause and effect reversed. The use of flash, at
long ranges will cause the camera to use ISO400, so you see the problem.
If there is enough light for ISO100, it is likely the flash didn't fire.


--
Ron Hunter (E-Mail Removed)
 
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Ron Hunter
Guest
Posts: n/a
 
      07-01-2005
Matt wrote:
> On Fri, 01 Jul 2005 15:22:23 -0400, Steven Feinstein
> <(E-Mail Removed)> wrote:
>
>
>>Scott W wrote:
>>
>>>Steven Feinstein wrote:
>>>
>>>
>>>>I have a Canon A95. Occassionally (and I'm trying to narrow down when)
>>>>I take a photo and I get small circular areas which are lighter than the
>>>>rest of the area. They remind me of what would happen when painting
>>>>watercolors and an area blooms (but it is a perfect circle).
>>>>
>>>>It seems to happen when the flash fires but the subject is too far away
>>>>or there are small areas of other sources of light. It also appears to
>>>>be worse at 400 ISO.
>>>>
>>>>I'm trying to figure out what is happening in order to avoid the
>>>>situation. If I had to make a guess, I'm thinking the shutter speed is
>>>>fast (because the flash is firing), but the flash is not bouncing off a
>>>>close object so the camera is picking up the light from the flash. Or
>>>>if there is a window maybe it is picking up some outfoor light peaking in.
>>>>
>>>>Has anyone else seen this? Does what I suggest sound plausible?
>>>>
>>>>Looking for some advice on the cause.
>>>>
>>>>Thanks,
>>>>
>>>>Steve
>>>
>>>
>>>It would help if we could see one of these photos.
>>>You might try aiming the camera straight up on a clear night and taking
>>>a flash photo.
>>>
>>>Scott
>>>

>>
>>I uploaded three images as examples. Dust does seem to make sense, it's
>>just that we took pictures at the same locations in a previous year
>>using a point and shoot film camera and did not have this problem. Does
>>it sound more like chance or is digital more sensitive to the dust?
>>
>>Light areas are:
>>lapel of man
>>knee of boy
>>above white banner
>>http://members.cox.net/sfein/images/img_1300.jpg
>>
>>Light areas are:
>>at bottom
>>on right near door
>>http://members.cox.net/sfein/images/img_1258.jpg
>>
>>Light areas are all over the place:
>>http://members.cox.net/sfein/images/img_1254.jpg
>>
>>I appreciate all the help from everyone.

>
>
> Classic ORBS
> http://homepage.ntlworld.com/h.cowell/orbs.htm
>
> I don't agree with the paranormal suggestions, since I was able to
> generate them on demand, by thumping a rather dusty chair and shooting
> it with flash.
>
> The classic digital ORB (always worse on digital) is caused by flash
> illumination/backscatter from near field dust, the point being
> defocused into a lightened circle.
>
> Of course, they show up worse on black.
> It also seems logical that they would be worse at high ISO, if the
> alternative is a wider aperture.
>
> They also seem to be common in church wedding photos - I guess it's
> the number of people that raises dust, and that you tend to be working
> at the outer end of flash range, so the flash is at maximum, and the
> relative nearfield illumination is greater
>
> There is no reason a film camera can't produce orb effects - a fixed
> focus compact would be most likely to, but they just don't seem to be
> as bad.
>

Probably because in a normal P&S camera, the sensor is quite small,
compared with the size of 35mm film, so the effects are more significant.


--
Ron Hunter (E-Mail Removed)
 
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Morton Linder
Guest
Posts: n/a
 
      07-02-2005
Ron Hunter wrote:
> Morton Linder wrote:
>
>> Steven Feinstein wrote:
>>
>>> Scott W wrote:
>>>
>>>> Steven Feinstein wrote:
>>>>
>>>>> I have a Canon A95. Occassionally (and I'm trying to narrow down
>>>>> when)
>>>>> I take a photo and I get small circular areas which are lighter
>>>>> than the
>>>>> rest of the area. They remind me of what would happen when painting
>>>>> watercolors and an area blooms (but it is a perfect circle).
>>>>>
>>>>> It seems to happen when the flash fires but the subject is too far
>>>>> away
>>>>> or there are small areas of other sources of light. It also
>>>>> appears to
>>>>> be worse at 400 ISO.
>>>>>
>>>>> I'm trying to figure out what is happening in order to avoid the
>>>>> situation. If I had to make a guess, I'm thinking the shutter
>>>>> speed is
>>>>> fast (because the flash is firing), but the flash is not bouncing
>>>>> off a
>>>>> close object so the camera is picking up the light from the flash. Or
>>>>> if there is a window maybe it is picking up some outfoor light
>>>>> peaking in.
>>>>>
>>>>> Has anyone else seen this? Does what I suggest sound plausible?
>>>>>
>>>>> Looking for some advice on the cause.
>>>>>
>>>>> Thanks,
>>>>>
>>>>> Steve
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> It would help if we could see one of these photos.
>>>> You might try aiming the camera straight up on a clear night and taking
>>>> a flash photo.
>>>>
>>>> Scott
>>>>
>>> I uploaded three images as examples. Dust does seem to make sense,
>>> it's just that we took pictures at the same locations in a previous
>>> year using a point and shoot film camera and did not have this
>>> problem. Does it sound more like chance or is digital more sensitive
>>> to the dust?
>>>
>>> Light areas are:
>>> lapel of man
>>> knee of boy
>>> above white banner
>>> http://members.cox.net/sfein/images/img_1300.jpg
>>>
>>> Light areas are:
>>> at bottom
>>> on right near door
>>> http://members.cox.net/sfein/images/img_1258.jpg
>>>
>>> Light areas are all over the place:
>>> http://members.cox.net/sfein/images/img_1254.jpg
>>>
>>> I appreciate all the help from everyone.

>>
>>
>> Hi,
>>
>> I noticed the same type of light circles, only with flash from a great
>> distance where the pictures were grossly underexposed, and were
>> presumably shot at ISO 400 (automatic) in my Canon S-500. I assumed
>> that it was a kind of digital "noise", and can't imagine why ISO 400
>> shows up dust more than ISO 100.
>>
>> Morton

>
>
> I believe you have the cause and effect reversed. The use of flash, at
> long ranges will cause the camera to use ISO400, so you see the problem.
> If there is enough light for ISO100, it is likely the flash didn't fire.
>
>

Not reversed. That is exactly what I said. I use "flash on" in low light
situations. As I said, I only see those circles at ISO 400 with long
distances and therefore underexposed pix.
Morton
 
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JPS@no.komm
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Posts: n/a
 
      07-02-2005
In message <zJlxe.4800$(E-Mail Removed)>,
Morton Linder <(E-Mail Removed)> wrote:

>As I said, I only see those circles at ISO 400 with long
>distances and therefore underexposed pix.


The further away the subject, the relatively closer the dust can be that
is lit by the flash and seen by the lens, and therefore, the brighter.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <(E-Mail Removed)>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

 
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Kevin McMurtrie
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      07-02-2005
In article <nSexe.22218$FP2.16918@lakeread03>,
Steven Feinstein <(E-Mail Removed)> wrote:

> I have a Canon A95. Occassionally (and I'm trying to narrow down when)
> I take a photo and I get small circular areas which are lighter than the
> rest of the area. They remind me of what would happen when painting
> watercolors and an area blooms (but it is a perfect circle).
>
> It seems to happen when the flash fires but the subject is too far away
> or there are small areas of other sources of light. It also appears to
> be worse at 400 ISO.
>
> I'm trying to figure out what is happening in order to avoid the
> situation. If I had to make a guess, I'm thinking the shutter speed is
> fast (because the flash is firing), but the flash is not bouncing off a
> close object so the camera is picking up the light from the flash. Or
> if there is a window maybe it is picking up some outfoor light peaking in.
>
> Has anyone else seen this? Does what I suggest sound plausible?
>
> Looking for some advice on the cause.
>
> Thanks,
>
> Steve


It's fabric lint in the air reflecting your flash.
 
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David J Taylor
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      07-02-2005
Steven Feinstein wrote:
[]
> Sorry David, I misinterpreted your message. I thought when you were
> comparing compact digital to larger cameras you meant larger digital
> cameras (i.e. DSLRs or even higher-end fixed lens). I did not think
> you meant vs film. So just to be sure, your description holds true
> for compact film cameras as well. The depth of filed is greater for
> compact digital vs compact film and most likely the flash is closer
> to the lens (which is true of my cameras).


Steve, I was trying to avoid emotive words like "point-and-shoot" and
"DSLR"!

There is a considerable difference in sensor size ( factor of five or
more), and therefore lens focal length, and therefore depth of field,
between point & shoot cameras and 35mm kit (meaning either film cameras or
DSLRs). This depth of field difference makes the flash-illuminated motes
more visible, as they will be less out-of-focus, and therefore present a
visible disk (which may be quite a large fraction of the image as you have
seen) rather than an "invisible" blur. Some digital cameras do have the
flash very close to the lens, which can mean that the path distance from
the flash to a more just in front of the lens may be a lot less than in
either a DSLR or a 35mm compact camera.

Your comment about underexposure, ISO 400, dark subjects, and flash at its
limiting distance are all factors which might make this effect more
visible. As you've observed, dust actually on the lens would appear at a
fixed location in the image (for a particular zoom setting), and perhaps
it's more difficult for the front lens surface to be illuminated by the
flash! Probably the best way to cure it is an off-camera flashgun.

I hope that clarifies what I meant.

Cheers,
David


 
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David J Taylor
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      07-02-2005
Belgos wrote:
[]
> I don't think that smaller DOF would help a lot with this - in any
> case the light circles are way out of focus.


Bear in mind that the difference between point-and-shoot and 35mm sensors
could be around 5 times in linear size, so the equialvent out-of-focus
light circle on 35mm might more than fill the frame, and simply be
perceived as a general contrast reduction or haze.

David


 
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