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Ghosting Problem



 
 
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  #1  
Old August 4th 04, 04:50 PM
Justin F. Knotzke
external usenet poster
 
Posts: n/a
Default Ghosting Problem

Hi,

http://www.shampoo.ca/gallery/lachin...7_2004/image13

This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached. Note that the arms of the rider in orange
appear where the tree nicely appears in the background.

Just so everyone knows, this isn't the effect I was going for. ;-) I was
hoping to get some rear curtain sync blur going but not having my subject's
face rubbed out..

If my assumption is correct, my thinking is that I need to decrease the
exposure by a stop or maybe more and then increase the flash output by a stop
or more.

Assuming this is all correct, is there a way I can figure out how many
stops I need to decreate exposure and increase flash exposure by?

I was thinking of maybe metering the sky, then metering the subject and
using the difference as my compensation factor..

Does that sound right?

Thanks

J



--
Justin F. Knotzke

http://www.shampoo.ca
  #2  
Old August 4th 04, 06:10 PM
Alan Browne
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Posts: n/a
Default Ghosting Problem

Justin F. Knotzke wrote:

Hi,

http://www.shampoo.ca/gallery/lachin...7_2004/image13


Cool shot.


This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached. Note that the arms of the rider in orange
appear where the tree nicely appears in the background.


They both have different color values (green/orange)... different
layers of color were used. Where the "white patch" shines
through is the same as the white sky in the BG. (all three color
layers react to white). (This is why when making multiple
exposure motion studies a black (or other dark) background is
usually used).

Just so everyone knows, this isn't the effect I was going for. ;-) I was
hoping to get some rear curtain sync blur going but not having my subject's
face rubbed out..


Well you do have some. Note that for a face to be well exposed
in a moving shot, the background must be dark. The lighter the
background, the less there is "left over" to record the flash
frozen subject.


If my assumption is correct, my thinking is that I need to decrease the
exposure by a stop or maybe more and then increase the flash output by a stop
or more.


Maybe. Notice how the redbrick buildings are already a bit
underexposed? Reducing the exposure will turn the buildings and
the trees to silhouettes. Flash? You can bring it down a stop
with the effect of the background bikers looking only like blurs
(no stop motion effect as is already evident in shot 13), and the
foreground bikers will maintain the strobe freeze). If you
increase the flash, you will get really high values and
reflections (note the skin highlights of the nearest biker on
13), but the background bikers will be more 'frozen'. Your choice.

The real issue here is the background needing to be dark enough
to not saturate the film where you want the bikers to be frozen.
If you reduce the exposure, then "white" sky will become greyer
and the trees/buildings will tend to silhouette. Solution:
capture the bikers where the BG is naturally dark.

Assuming this is all correct, is there a way I can figure out how many
stops I need to decreate exposure and increase flash exposure by?


As you're looking to have a "normal" looking BG, you need to
expose for it ... the flash will not help with it at all.

Since flash does not care about shutter time (as long as you make
sync speed), then think of it all in terms of where you want your
speed for the blur effect (about 1/30 to 1/15 in this case?)
and then set the aperture for that speed to expose the background
properly.


I was thinking of maybe metering the sky, then metering the subject and
using the difference as my compensation factor..


Slide film? If you meter a white sky, then open up 1.7 to 2
stops (of aperture as your speed is predtermined for blur in this
case), if you meter a blue sky, then 1 stop will do. That will
give you the non-flash portion of the image.

The flash portion of the image is dictated by the TTL flash
system. Assuming you're using the F5, this should be minimally
complex and there should be little reason to flash compensate
with these subjects... in your shots the jersey reds are nicely
saturated.)

I like your series of cycling shots, BTW!

Cheers,
Alan


--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

  #3  
Old August 4th 04, 06:10 PM
Alan Browne
external usenet poster
 
Posts: n/a
Default Ghosting Problem

Justin F. Knotzke wrote:

Hi,

http://www.shampoo.ca/gallery/lachin...7_2004/image13


Cool shot.


This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached. Note that the arms of the rider in orange
appear where the tree nicely appears in the background.


They both have different color values (green/orange)... different
layers of color were used. Where the "white patch" shines
through is the same as the white sky in the BG. (all three color
layers react to white). (This is why when making multiple
exposure motion studies a black (or other dark) background is
usually used).

Just so everyone knows, this isn't the effect I was going for. ;-) I was
hoping to get some rear curtain sync blur going but not having my subject's
face rubbed out..


Well you do have some. Note that for a face to be well exposed
in a moving shot, the background must be dark. The lighter the
background, the less there is "left over" to record the flash
frozen subject.


If my assumption is correct, my thinking is that I need to decrease the
exposure by a stop or maybe more and then increase the flash output by a stop
or more.


Maybe. Notice how the redbrick buildings are already a bit
underexposed? Reducing the exposure will turn the buildings and
the trees to silhouettes. Flash? You can bring it down a stop
with the effect of the background bikers looking only like blurs
(no stop motion effect as is already evident in shot 13), and the
foreground bikers will maintain the strobe freeze). If you
increase the flash, you will get really high values and
reflections (note the skin highlights of the nearest biker on
13), but the background bikers will be more 'frozen'. Your choice.

The real issue here is the background needing to be dark enough
to not saturate the film where you want the bikers to be frozen.
If you reduce the exposure, then "white" sky will become greyer
and the trees/buildings will tend to silhouette. Solution:
capture the bikers where the BG is naturally dark.

Assuming this is all correct, is there a way I can figure out how many
stops I need to decreate exposure and increase flash exposure by?


As you're looking to have a "normal" looking BG, you need to
expose for it ... the flash will not help with it at all.

Since flash does not care about shutter time (as long as you make
sync speed), then think of it all in terms of where you want your
speed for the blur effect (about 1/30 to 1/15 in this case?)
and then set the aperture for that speed to expose the background
properly.


I was thinking of maybe metering the sky, then metering the subject and
using the difference as my compensation factor..


Slide film? If you meter a white sky, then open up 1.7 to 2
stops (of aperture as your speed is predtermined for blur in this
case), if you meter a blue sky, then 1 stop will do. That will
give you the non-flash portion of the image.

The flash portion of the image is dictated by the TTL flash
system. Assuming you're using the F5, this should be minimally
complex and there should be little reason to flash compensate
with these subjects... in your shots the jersey reds are nicely
saturated.)

I like your series of cycling shots, BTW!

Cheers,
Alan


--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--

  #4  
Old August 4th 04, 07:31 PM
McLeod
external usenet poster
 
Posts: n/a
Default Ghosting Problem

On 4 Aug 2004 15:50:46 GMT, "Justin F. Knotzke"
wrote:

Hi,

http://www.shampoo.ca/gallery/lachin...7_2004/image13

This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached. Note that the arms of the rider in orange
appear where the tree nicely appears in the background.

Just so everyone knows, this isn't the effect I was going for. ;-) I was
hoping to get some rear curtain sync blur going but not having my subject's
face rubbed out..

If my assumption is correct, my thinking is that I need to decrease the
exposure by a stop or maybe more and then increase the flash output by a stop
or more.

Assuming this is all correct, is there a way I can figure out how many
stops I need to decreate exposure and increase flash exposure by?

I was thinking of maybe metering the sky, then metering the subject and
using the difference as my compensation factor..

Does that sound right?

Thanks

J


The problem is the fact that you have, in effect, two exposures. I
don't know whether you're shooting digital or slide or negative but
with positives the area of the sky is so overexposed there is no data
left anyway. Your flash exposure seems good and your ambient
exposure, at least for the street and trees is already underexposed.
Can you change your camera height? If you shot slightly down you
would have perfect results. Or change your point of aim so there is a
darker background behind your subjects. The lighter your background
is the more pronounced the ghosting effect will be.
  #5  
Old August 4th 04, 07:31 PM
McLeod
external usenet poster
 
Posts: n/a
Default Ghosting Problem

On 4 Aug 2004 15:50:46 GMT, "Justin F. Knotzke"
wrote:

Hi,

http://www.shampoo.ca/gallery/lachin...7_2004/image13

This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached. Note that the arms of the rider in orange
appear where the tree nicely appears in the background.

Just so everyone knows, this isn't the effect I was going for. ;-) I was
hoping to get some rear curtain sync blur going but not having my subject's
face rubbed out..

If my assumption is correct, my thinking is that I need to decrease the
exposure by a stop or maybe more and then increase the flash output by a stop
or more.

Assuming this is all correct, is there a way I can figure out how many
stops I need to decreate exposure and increase flash exposure by?

I was thinking of maybe metering the sky, then metering the subject and
using the difference as my compensation factor..

Does that sound right?

Thanks

J


The problem is the fact that you have, in effect, two exposures. I
don't know whether you're shooting digital or slide or negative but
with positives the area of the sky is so overexposed there is no data
left anyway. Your flash exposure seems good and your ambient
exposure, at least for the street and trees is already underexposed.
Can you change your camera height? If you shot slightly down you
would have perfect results. Or change your point of aim so there is a
darker background behind your subjects. The lighter your background
is the more pronounced the ghosting effect will be.
  #6  
Old August 5th 04, 01:42 AM
Annika1980
external usenet poster
 
Posts: n/a
Default Ghosting Problem

This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached.


That effect happens when you choose a slow shutter speed for the background
exposure and then attempt to freeze the foreground action with flash.
I've got a few ghost hummingbird shots that way as well.





  #7  
Old August 5th 04, 01:42 AM
Annika1980
external usenet poster
 
Posts: n/a
Default Ghosting Problem

This ghosting and complete white out appears to be happening because the
D-MAX of my film is being reached.


That effect happens when you choose a slow shutter speed for the background
exposure and then attempt to freeze the foreground action with flash.
I've got a few ghost hummingbird shots that way as well.





  #8  
Old August 5th 04, 03:42 PM
Justin F. Knotzke
external usenet poster
 
Posts: n/a
Default Ghosting Problem

quote who= Alan Browne /:

The real issue here is the background needing to be dark enough
to not saturate the film where you want the bikers to be frozen.
If you reduce the exposure, then "white" sky will become greyer
and the trees/buildings will tend to silhouette. Solution:
capture the bikers where the BG is naturally dark.


Hmm I suppose. Easier said then done of course. ;-) They are flyin by at
45km/h.. But I see your point. I'll try to setup pointing a little more to the
right. There's a block of trees there..

Slide film? If you meter a white sky, then open up 1.7 to 2
stops (of aperture as your speed is predtermined for blur in this
case), if you meter a blue sky, then 1 stop will do. That will
give you the non-flash portion of the image.

The flash portion of the image is dictated by the TTL flash
system. Assuming you're using the F5, this should be minimally
complex and there should be little reason to flash compensate
with these subjects... in your shots the jersey reds are nicely
saturated.)


Ok. I think I follow you. I had to read your post a few times to get it.
But the idea is to expose for the background, and let the flash do the rest. I
use the flash to get out facial expressions. Helmets and sunglasses are great
for the riders, but crappy for the photogs. I can get eyeballs and suffer
faces much better with the flash then without.

At first I was dead against using a flash for anything unless required. Now
I am starting to really see the advantage. It gives me better contrast, makes
my subjects pop out.

In late August when the final races come up, the race ends in almost
darkness. I was dreaming of setting up 3 or 4 alien bees with pocket wizards on
one corner and firing away. I'd have two at the front pointing up and two at
the back pointing down.

I'd probably cause a massive crash though. ;-)

Oh and yes, I am using the F5 and I am shooting Sensia or HP5+ (depending
on how much money I have left in the account that week grin).

I've been shooting this race now for about 4 weeks and I am learning tons.
A lot of guys show up with monster glass (300 F2.8) and stand on the same
corner and wait.. I can't see how that's going to get you a great image. Even
with glass that long, you still have the problem of riders getting in the way
or other riders. You are mostly stuck with shooting the guys in the lead. I'm
using 80mm and getting in so close that I think some of the riders are trying
to knock the camera out of my hands.

I still want an 80-200 F2.8 though. ;-) B&H has one for $475USD used..
Anyone wanna buy a... oh crap, I have nothing left to sell.

I like your series of cycling shots, BTW!


Thanks Alan. Much appreciated.

J

--
Justin F. Knotzke

http://www.shampoo.ca
  #9  
Old August 5th 04, 03:42 PM
Justin F. Knotzke
external usenet poster
 
Posts: n/a
Default Ghosting Problem

quote who= Alan Browne /:

The real issue here is the background needing to be dark enough
to not saturate the film where you want the bikers to be frozen.
If you reduce the exposure, then "white" sky will become greyer
and the trees/buildings will tend to silhouette. Solution:
capture the bikers where the BG is naturally dark.


Hmm I suppose. Easier said then done of course. ;-) They are flyin by at
45km/h.. But I see your point. I'll try to setup pointing a little more to the
right. There's a block of trees there..

Slide film? If you meter a white sky, then open up 1.7 to 2
stops (of aperture as your speed is predtermined for blur in this
case), if you meter a blue sky, then 1 stop will do. That will
give you the non-flash portion of the image.

The flash portion of the image is dictated by the TTL flash
system. Assuming you're using the F5, this should be minimally
complex and there should be little reason to flash compensate
with these subjects... in your shots the jersey reds are nicely
saturated.)


Ok. I think I follow you. I had to read your post a few times to get it.
But the idea is to expose for the background, and let the flash do the rest. I
use the flash to get out facial expressions. Helmets and sunglasses are great
for the riders, but crappy for the photogs. I can get eyeballs and suffer
faces much better with the flash then without.

At first I was dead against using a flash for anything unless required. Now
I am starting to really see the advantage. It gives me better contrast, makes
my subjects pop out.

In late August when the final races come up, the race ends in almost
darkness. I was dreaming of setting up 3 or 4 alien bees with pocket wizards on
one corner and firing away. I'd have two at the front pointing up and two at
the back pointing down.

I'd probably cause a massive crash though. ;-)

Oh and yes, I am using the F5 and I am shooting Sensia or HP5+ (depending
on how much money I have left in the account that week grin).

I've been shooting this race now for about 4 weeks and I am learning tons.
A lot of guys show up with monster glass (300 F2.8) and stand on the same
corner and wait.. I can't see how that's going to get you a great image. Even
with glass that long, you still have the problem of riders getting in the way
or other riders. You are mostly stuck with shooting the guys in the lead. I'm
using 80mm and getting in so close that I think some of the riders are trying
to knock the camera out of my hands.

I still want an 80-200 F2.8 though. ;-) B&H has one for $475USD used..
Anyone wanna buy a... oh crap, I have nothing left to sell.

I like your series of cycling shots, BTW!


Thanks Alan. Much appreciated.

J

--
Justin F. Knotzke

http://www.shampoo.ca
  #10  
Old August 5th 04, 03:53 PM
Justin F. Knotzke
external usenet poster
 
Posts: n/a
Default Ghosting Problem

quote who= McLeod /:

The problem is the fact that you have, in effect, two exposures. I
don't know whether you're shooting digital or slide or negative but
with positives the area of the sky is so overexposed there is no data
left anyway. Your flash exposure seems good and your ambient
exposure, at least for the street and trees is already underexposed.
Can you change your camera height? If you shot slightly down you
would have perfect results. Or change your point of aim so there is a
darker background behind your subjects. The lighter your background
is the more pronounced the ghosting effect will be.


Ya. I figured as much. Thanks for the reply. I have shot some pointing
downwards:

Not great shots, but as you can see, no major ghosting..

http://www.shampoo.ca/gallery/lachin...20_2004/image7
http://www.shampoo.ca/gallery/lachin...27_2004/image1

Same corner as where the ghosting image happened but pointing more where
the trees are.

http://www.shampoo.ca/gallery/lachin...27_2004/image7

Anyhow, this goes to prove your point that finding a dark background makes
all the difference.

Thanks for the reply,

J


--
Justin F. Knotzke

http://www.shampoo.ca
 




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