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What causes this discoloration in some photos
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Mar 2, 2012 17:36:29   #
achammar Loc: Idaho
 
I have some images that have strange color problems in the skin. Some do, and some don't, even when taken close together from the same spot.
Here are 2 examples, one taken right after the other one..
The first one has a rough greenish color on her arm and face, the second is fine. Both were taken from the same distance and in the same spot. I did have my ISO set really high, and I don't remember why now.....I may just not have noticed it was set that high. These are just crops of the entire picture and the skin is where the problem is. These are original untouched images straight off my card (other than the cropping)
I know my ISO should have been less and the exposure time maybe increased and my f stop opened up more , but is that what the problem is here?

I was using a Nikon D60 with an SB600 flash mounted to the camera
Settings for photo 1:
F stop = f13
1/160 exposure time
ISO 800
Focal length 30
With flash

Settings for photo 2 (exposure time is the only difference)

F stop = f13
1/100 exposure time
ISO 800
Focal length 30
With flash

Anyone know the reason for the green rough colors in picture 1?

(Actually I do remember why I had my f stop set so small. The background was a very large window and I was trying to avoid overexposure of the light outside)....

Problem picture
Problem picture...

Good picture (very next shot)
Good picture (very next shot)...

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Mar 2, 2012 17:53:46   #
Erv Loc: Medina Ohio
 
Looks to me like your flash didn't fire. You can look at the metadata and see the settings. It will tell you. Are you giving it enough time to recycle?
Erv

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Mar 2, 2012 18:06:47   #
achammar Loc: Idaho
 
Thanks Erv!
I just checked the file info with photoshop and it says the flash fired on both images. I'm not sure though that my flash won't fire even if it's not recycled all the way yet though. It might fire anyway, but not to the extent it should if it's not all the way ready...
So you think it might just be there was not enough light?

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Mar 2, 2012 18:27:44   #
Erv Loc: Medina Ohio
 
With the color of her dress, i would say if it fired it didn't put out much light. See how white the dress is in the second shot, that is your flash making it a true white. I would play with it and watch it. Were the batteries good? Put new batteries in and see if you might have had a bad battery. Do you have a tester for batteries? If you could test them, only one bad battery will cause all kinds of things.
Erv

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Mar 2, 2012 18:48:23   #
achammar Loc: Idaho
 
Erv wrote:
With the color of her dress, i would say if it fired it didn't put out much light. See how white the dress is in the second shot, that is your flash making it a true white. I would play with it and watch it. Were the batteries good? Put new batteries in and see if you might have had a bad battery. Do you have a tester for batteries? If you could test them, only one bad battery will cause all kinds of things.
Erv


I'm thinking now it was because the flash fired at only partial it's strength. I will have to test that to see, but I would almost bet on it. I put brand new alkaline batteries in before every shoot, whether it needs it or not. That doesn't leave out the fact that 1 could be bad, but most of the pictures turned out fine. (I do have a battery tester that I think that is a good idea to test every battery before I put it in...better safe than sorry...) I did go through and look at a bunch, and it's only the darker ones that have that problem, and there were times where I didn't wait very long before shots. I think that's the problem, although I didn't know low light would cause that (but it's probably a combination of the settings I used too), but at least I know enough light will prevent it...:-)

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Mar 2, 2012 20:21:56   #
Dudley Loc: Roseburg, Oregon
 
achammar wrote:
Erv wrote:
With the color of her dress, i would say if it fired it didn't put out much light. See how white the dress is in the second shot, that is your flash making it a true white. I would play with it and watch it. Were the batteries good? Put new batteries in and see if you might have had a bad battery. Do you have a tester for batteries? If you could test them, only one bad battery will cause all kinds of things.
Erv


I'm thinking now it was because the flash fired at only partial it's strength. I will have to test that to see, but I would almost bet on it. I put brand new alkaline batteries in before every shoot, whether it needs it or not. That doesn't leave out the fact that 1 could be bad, but most of the pictures turned out fine. (I do have a battery tester that I think that is a good idea to test every battery before I put it in...better safe than sorry...) I did go through and look at a bunch, and it's only the darker ones that have that problem, and there were times where I didn't wait very long before shots. I think that's the problem, although I didn't know low light would cause that (but it's probably a combination of the settings I used too), but at least I know enough light will prevent it...:-)
quote=Erv With the color of her dress, i would sa... (show quote)


As I understand the situation, most flash systems don't fire (even if the flash ready light comes on) because the system is not ready for work.

I would also caution using a flash against a highly reflective surface (such as an interior wall, or window.)

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Mar 3, 2012 03:17:59   #
wessyfiesta Loc: wakefield united kingdom
 
I would have to say the flash did not fire on the first pic, as there is alot of noise in the photo, due to having high iso, the second photo has got flash as you can tell with the bright colours in the dress,i think you need to look at your flash.

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Mar 3, 2012 09:02:50   #
RoysJungle Loc: Ohio
 
To me the problem is that you are using to high of an ISO which introduces noise into the picture. By decreasing the aperture, you can decrease your ISO and still produce the same exposure at the same shutter speed, which I wouldn't go below what speed you shot at or you start getting blur from her moving. In addition, by decreasing the aperture you will produce a better picture by blurring the distracting elements in the background, such as the SUV in the second picture.

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Mar 3, 2012 09:06:03   #
twowindsbear
 
YES the flash DID fire in BOTH pix. Look at the bright reflections from the sequins near her elbow, and the reflections from her earrings in the first pic. I think the difference is the exposure times 1/160 for the first & 1/100 for the second. And, the flash may have been ever so slightly more 'powerful' in the second. I think you did a good job balancing the flash & the natural light. I don't see the 'green' in either pic - I guess that's because of the lower resolution on my computer.

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Mar 3, 2012 10:48:02   #
ward5311 Loc: Georgia
 
I also would check ISO...Looks grainy to me...Just my .02 :D

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Mar 3, 2012 11:05:29   #
Lucian Loc: From Wales, living in Ohio
 
ERV has it right your flash may well have fired however, there was not enough power being put out, THAT is why you have all that noise/grain in the image. Your flash will fire even when there is not sufficient energy built up to allow a full power shot.

I have Nikons and the SB800 which is more powerful than your SB600 and I can tell you there are often cases where the ready light shows in the camera but the flash still has not built up enough juice to correctly expose the scene. Just be aware of this problem and always wait until you see the ready light on the flash itself light up, before firing.

Your ISO would not help the outside exposure really, your aperture and shutter setting controls that. Remember that when using flash, your shutter controls ambient light, the light outside or in the room and your aperture ONLY, controls the flash exposure on your subject. I don't trust the TTL so I mostly use manual setting when doing flash, TTL works sometimes but not too well at other times.

You could set your camera to P-mode and then adjust your exposure compensation button, the plus and minus, to add or subtract light when using flash in TTL mode, to get the correct exposure you need. But your problem with your posted images is simply that the darker image did not have sufficient power in the flash to correctly expose the subject matter. It makes no difference what batteries you use, if it flash has not fully charged despite showing it may have, it will not let you take a correctly exposed image.

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Mar 3, 2012 12:36:05   #
achammar Loc: Idaho
 
Lucian wrote:
ERV has it right your flash may well have fired however, there was not enough power being put out, THAT is why you have all that noise/grain in the image. Your flash will fire even when there is not sufficient energy built up to allow a full power shot.

I have Nikons and the SB800 which is more powerful than your SB600 and I can tell you there are often cases where the ready light shows in the camera but the flash still has not built up enough juice to correctly expose the scene. Just be aware of this problem and always wait until you see the ready light on the flash itself light up, before firing.

Your ISO would not help the outside exposure really, your aperture and shutter setting controls that. Remember that when using flash, your shutter controls ambient light, the light outside or in the room and your aperture ONLY, controls the flash exposure on your subject. I don't trust the TTL so I mostly use manual setting when doing flash, TTL works sometimes but not too well at other times.

You could set your camera to P-mode and then adjust your exposure compensation button, the plus and minus, to add or subtract light when using flash in TTL mode, to get the correct exposure you need. But your problem with your posted images is simply that the darker image did not have sufficient power in the flash to correctly expose the subject matter. It makes no difference what batteries you use, if it flash has not fully charged despite showing it may have, it will not let you take a correctly exposed image.
ERV has it right your flash may well have fired ho... (show quote)


I believe that is exactly what happened. But according to what you have told me here, I was doing it backwards. I had a small aperture thinking that would decrease overexposure of the light outside the window. I just set the shutter speed to match the amount of light I needed for a good exposure on my subject. I'm very limited on my shutter speed though when using a flash. The fastest it will go is 1/200, so I couldn't have opened up my aperture much. But I will try it that way next time. Maybe set my shutter speed at 1/200, and set my ISO and/or aperture to match what I need to get a good exposure on my subject...
Thanks!

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Mar 3, 2012 16:04:24   #
Lucian Loc: From Wales, living in Ohio
 
Read everything here, it will be well worth your while. The best way to think about it is with a manual set flash. Move it close to subject and you need a small aperture, shutter does not matter much if in a darkened room. Move the flash on manual and at full power, further away and you need to open up a little more as the distance grows, again the shutter speed matters little. Practice will tell you what distance you need what f-stop to get a correct exposure each time, as long as you set the flash to full power and manual.

Yes there are other settings for example you can set it close but at 1/4 power instead of changing the f-stop but then we are throwing into the mix, too many variable for you to understand. Once you have grasped the concept here, then you can begin to explore things in more detail with changing of flash intensity and f-stop variables etc. But not now.

So then, back to where we were, in that darkened room. Say we had the shutter set at 200th and then changed it to 125th and then to 80th as an example. You would not see anything change at all in your image, the subject would be correctly exposed, assuming you had set the flash distance and aperture correctly at some point,in order to be consistent. So to recap, you would have a dark background, assuming that you had the subject away from the wall, lets say in the middle of a large room or in a hall, and the subject would have been correctly exposed from the flash (Distance/power setting/f-stop).

Now, with out changing anything else, you would have seen that the 3 different shutter speeds would have not changed your background much, if anything at all. It looked black/blackish each time regardless of the three changes you made. But... let's say you wanted to get the ambient light in the room to show up on the image, as well as have the subject correctly exposed. Now you need to play with shutter speed.

The longer the shutter speed the more ambient light is allowed to paint onto your camera sensor. This will not affect your subject, unless the ambient light is rather bright. If it is bright then you won't need to open up the shutter as much in order to get the background to show up on the print.

If it is as dark as say a wedding evening reception, then you may need to slow the shutter down to 50th or 30th or even 15th to get it to show up. Your subject, in such dark ambient light conditions would not change as long as you did not change the f-stop or distance/power of your flash to the subject. So now you would get the background to show up and still have a correctly exposed subject.

One point to bear in mind, if there is movement of the subject, the slower the shutter speed and the greater the ambient light, the more likely you will get some ghosting showing up on your subject, though the flash will still hold the features sharp. So if you had a fast shutter speed, say from 80th through 200th and medium ambient light and they were running past you, your shot would get them frozen in time and the background would be dark to black.

If you slowed the shutter speed to say 60th or 45th, you may now be getting something show up of the background but it would be slightly blurred as you panned across the room to shoot the running subject, and the subject would still show up sharp from the flash.

Now if you were at a shutter speed of say 30th to 15th, you would probably get a sharp looking image of your subject running from the flash, however, you will most likely end up with some streaky ghosting of the image behind the flashed crisp part of your subject.

Your camera can be set to front or back curtain which means it either shoots the flash at the start or end of the shutter speed setting. On a slow shutter setting this would mean the subject is sharp and the streaking from ambient light travels to the right of the subject, assuming they were running left to right of the camera as you looked at them, or it would show the streaking as if it was following them and then the sharp image of the subject correctly exposed. Generally it is best to have the streaky bits behind the movement of the subject, not in front of the movement.

Now with this new found knowledge go out into the world (dimly lit room) and practice to see what you need to do to get the effects I mentioned above. Then and only then will you better understand your camera and the relation flash plays, coupled with your settings of flash/f-stop/shutter speeds to achieve the effect you wish. This lesson was free, the rest I'll be charging for!

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Mar 3, 2012 17:14:50   #
achammar Loc: Idaho
 
Lucian wrote:
Read everything here, it will be well worth your while. The best way to think about it is with a manual set flash. Move it close to subject and you need a small aperture, shutter does not matter much if in a darkened room. Move the flash on manual and at full power, further away and you need to open up a little more as the distance grows, again the shutter speed matters little. Practice will tell you what distance you need what f-stop to get a correct exposure each time, as long as you set the flash to full power and manual.

Yes there are other settings for example you can set it close but at 1/4 power instead of changing the f-stop but then we are throwing into the mix, too many variable for you to understand. Once you have grasped the concept here, then you can begin to explore things in more detail with changing of flash intensity and f-stop variables etc. But not now.

So then, back to where we were, in that darkened room. Say we had the shutter set at 200th and then changed it to 125th and then to 80th as an example. You would not see anything change at all in your image, the subject would be correctly exposed, assuming you had set the flash distance and aperture correctly at some point,in order to be consistent. So to recap, you would have a dark background, assuming that you had the subject away from the wall, lets say in the middle of a large room or in a hall, and the subject would have been correctly exposed from the flash (Distance/power setting/f-stop).

Now, with out changing anything else, you would have seen that the 3 different shutter speeds would have not changed your background much, if anything at all. It looked black/blackish each time regardless of the three changes you made. But... let's say you wanted to get the ambient light in the room to show up on the image, as well as have the subject correctly exposed. Now you need to play with shutter speed.

The longer the shutter speed the more ambient light is allowed to paint onto your camera sensor. This will not affect your subject, unless the ambient light is rather bright. If it is bright then you won't need to open up the shutter as much in order to get the background to show up on the print.

If it is as dark as say a wedding evening reception, then you may need to slow the shutter down to 50th or 30th or even 15th to get it to show up. Your subject, in such dark ambient light conditions would not change as long as you did not change the f-stop or distance/power of your flash to the subject. So now you would get the background to show up and still have a correctly exposed subject.

One point to bear in mind, if there is movement of the subject, the slower the shutter speed and the greater the ambient light, the more likely you will get some ghosting showing up on your subject, though the flash will still hold the features sharp. So if you had a fast shutter speed, say from 80th through 200th and medium ambient light and they were running past you, your shot would get them frozen in time and the background would be dark to black.

If you slowed the shutter speed to say 60th or 45th, you may now be getting something show up of the background but it would be slightly blurred as you panned across the room to shoot the running subject, and the subject would still show up sharp from the flash.

Now if you were at a shutter speed of say 30th to 15th, you would probably get a sharp looking image of your subject running from the flash, however, you will most likely end up with some streaky ghosting of the image behind the flashed crisp part of your subject.

Your camera can be set to front or back curtain which means it either shoots the flash at the start or end of the shutter speed setting. On a slow shutter setting this would mean the subject is sharp and the streaking from ambient light travels to the right of the subject, assuming they were running left to right of the camera as you looked at them, or it would show the streaking as if it was following them and then the sharp image of the subject correctly exposed. Generally it is best to have the streaky bits behind the movement of the subject, not in front of the movement.

Now with this new found knowledge go out into the world (dimly lit room) and practice to see what you need to do to get the effects I mentioned above. Then and only then will you better understand your camera and the relation flash plays, coupled with your settings of flash/f-stop/shutter speeds to achieve the effect you wish. This lesson was free, the rest I'll be charging for!
Read everything here, it will be well worth your w... (show quote)


This was a very good tutorial...I couldn't of found anything that good online! Thanks for that information. This information tells me a LOT. I will memorize these words well. Thank you! :-)

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Mar 3, 2012 20:20:57   #
pfredd
 
Shutter speed differs a bit more than 1/2 stop, but is no problem since it is controlling only outside light and looks right for sky exp. Saturation difference might come from a passing cloud, but it does make one wondr.
I don.t see green cast here, bit do see footprint of it. When adjusting levels for each exposure both pix look equal then reading skin colour they are same — however #1 captured a better range of whites. #2 feels a bit warmer even though the skin tones re equal after levels adjustment.
Of course both flashed, output of #1 was less. Possible causes well cover in earlier replies. Nice if you can identify for future even while the result here is very easily corrected.

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