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Archive 2013 · Please help to identify the problem!
  
 
phuang3
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p.1 #1 · p.1 #1 · Please help to identify the problem!


My friend sent me a picture today and asked what could possibly cause this phenomena. He said he got roughly 1:100 of this kind of picture. Another one is purple. It's taken by Canon 7D with 580EX flash. (not YN-560, sorry) W/B was set to flash.

Canon 7D 1/80s 85/1.2L@f4. No florescent light nearby.
http://kspqm.kymco.com/ckfinder/resource/johnny/image/IMG_8584s2.JPG

Edited on Feb 22, 2013 at 05:15 AM · View previous versions



Feb 20, 2013 at 12:34 PM
cgardner
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p.1 #2 · p.1 #2 · Please help to identify the problem!


Difficult to diagnose from one photo but seems more likely to be a random camera problem not one related to the flash.

Was he shooting RAW? If so go back to the RAW and look at the temp / tint values in the off color files versus the normal ones.

Also you might want to repost a smaller file (a 600 x 900 Level 6 JPG would suffice) so it will load faster.



Feb 20, 2013 at 01:24 PM
RustyBug
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p.1 #3 · p.1 #3 · Please help to identify the problem!


Do you have the magenta one that you can post also ... and a regular one. +1 @ RAW data review also.

Looking at the channels, the blue channel looks reasonable, while it kinda looks like the red channel somehow "donated" (or is mia) its share to the green channel. I'm assuming she is wearing some shade of red lipstick. It is showing black in the red channel, but light gray in the green channel which would be too light for a red in the green channel.

Curious to see how this compares with the purple version. It makes me think that the camera somehow assigned the information collected in the individual channels and somehow combined the R&G into just the G. I suspect the purple version will have a similar channel over/under response. I realize I'm outa my league on this one, but that's how it strikes me.


The thing that comes to mind from a lighting perspective is if your ambient was absent of red due to being very cyanic (skylight, north light, stained glass) with sufficient illumination (see green channel @ overexposure??) that your flash contributed very little to the color. @ 1/80, f4, ISO 800 @ 2PM, that could be sufficient illumination that you're flash was very low, or a misfire of some sort wasn't noticed. As to the purple, it would require some other kind of ambient influence (inverse) coupled with a low power/misfire scenario and sufficient ambient exposure.

BTW, what was the position of the flash?

Obviously, I"m grappling and grasping a bit here, but it's all I've got atm ... maybe it'll spark a clue elsewhere.


Here's a save effort via channels.










Red Channel







Green Channel







Blue Channel



Edited on Feb 20, 2013 at 05:00 PM · View previous versions



Feb 20, 2013 at 03:00 PM
kenyee
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p.1 #4 · p.1 #4 · Please help to identify the problem!


Bad memory card would be my guess if it's not a bad camera...



Feb 20, 2013 at 04:29 PM
RustyBug
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p.1 #5 · p.1 #5 · Please help to identify the problem!


Here's a strong hue shift of -123 and some desaturation.

This kinda looks like there was incandescent ambient, coupled with a very low power;misfire from the flash, and the WB misalignment @ incandescent wreaked havoc on the shift.

Either way, I'm beginning to think this was a misfire or too much ambient expsoure, resulting in a mismatch of flash, ambient & WB, Any chance your friend "auto" or "click" adjusted the WB, or processed this along with some others (maybe without a low power/misfire)? The strong hue shift bringing things along as this makes me wonder what/when/where an adjustment to the WB was assigned/adjusted.

A plausible scenario ...
Specular flash reflection fools flash to underpower.
Insufficient flash illumination, exposure is from ambient.
Ambient is not balanced with WB, major shift occurs.

Took a stab at a color version salvage from a renewed persepective.
Likely not very close to actual, but I'd like to think the last one is an improvement over the OP.












Feb 20, 2013 at 05:04 PM
400d
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p.1 #6 · p.1 #6 · Please help to identify the problem!


EXIF data doesn't say it's set to flash, it's manual WB. Ask him for the CR2 file.


Feb 20, 2013 at 10:08 PM
RustyBug
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p.1 #7 · p.1 #7 · Please help to identify the problem!


<exif:ExposureProgram>1</exif:ExposureProgram>
<exif:ISOSpeedRatings>
<rdf:Seq>
<rdf:li>800</rdf:li>


<exif:MeteringMode>6</exif:MeteringMode>
<exif:Flash rdf: parseType="Resource">
<exif:Fired>True</exif:Fired>
<exif:Return>0</exif:Return>
</exif:Flash>

<exif:ExposureMode>1</exif:ExposureMode>
<exif:WhiteBalance>1</exif:WhiteBalance>



Feb 20, 2013 at 10:55 PM
visualist
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p.1 #8 · p.1 #8 · Please help to identify the problem!


kenyee wrote:
Bad memory card would be my guess if it's not a bad camera...


Yepp, most certainly a memory / conversion problem. Though with both camera or card, a restart / format should solve the problem.



Feb 21, 2013 at 02:22 PM
RustyBug
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p.1 #9 · p.1 #9 · Please help to identify the problem!


visualist wrote:
Yepp, most certainly a memory / conversion problem. Though with both camera or card, a restart / format should solve the problem.


I'm not versed in memory issues, would be good to learn a bit more, thanks.

You say that with a degree of certainty ... based on ... how can you tell? How does a reformat fix it/prevent it in the future?




Feb 21, 2013 at 03:39 PM
400d
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p.1 #10 · p.1 #10 · Please help to identify the problem!





Feb 21, 2013 at 07:41 PM
 

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BrianO
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p.1 #11 · p.1 #11 · Please help to identify the problem!


kenyee wrote:
Bad memory card would be my guess if it's not a bad camera...


visualist wrote:
Yepp, most certainly a memory / conversion problem. Though with both camera or card, a restart / format should solve the problem.


RustyBug wrote:
You say that with a degree of certainty ... based on ... how can you tell? How does a reformat fix it/prevent it in the future?


Unless the shot was made under a green light, it's almost certain that the problem was the red and blue channels not being recorded properly. If all the shots were that way, it could be a sensor issue, but if it's only one in a hundred it's more likely somewhere in the I/O stream. Previous experience suggests to me that it's a card fault, although it could be in the camera.

Reformatting the card sometimes cures recording issues by unscrambling the file allocation structure. (When the card is scrambled, the three channels may not record to the same area, and one or more channel can get "lost" in the mix.) The more photos that have been individually deleted -- as opposed to formatting the whole card -- the more likely this is to happen, although it's still pretty rare in my experience. (I've only had one photo not record properly, and in that case the top half was fine but the bottom was scrambled. My uncle, though, had this exact issue happen to him, and data recovery software was only able to restore a few of them. He reformatted the card, and no more problems.)


Edited on Feb 23, 2013 at 03:22 AM · View previous versions



Feb 21, 2013 at 11:10 PM
RustyBug
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p.1 #12 · p.1 #12 · Please help to identify the problem!


Thanks Brian ... I think I followed that.

The OP mentioned the other one being "purple" ... could it be that the R&B that is absent here (rendering the green dominance), were sent to the other file, giving it the excess necessary to generate the purple? Kind of a "rob Peter to pay Paul" thing with the R&B info being misplaced into the wrong file?

Now, I really want to see the "purple" one.




Feb 21, 2013 at 11:46 PM
BrianO
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p.1 #13 · p.1 #13 · Please help to identify the problem!


RustyBug wrote:
...The OP mentioned the other one being "purple" ... could it be that the R&B that is absent here (rendering the green dominance), were sent to the other file, giving it the excess necessary to generate the purple?


More likely that on the purple shot shot the green channel got lost, so only the red and blue channels were showing. That's just a guess, though, without actually studying the files.



Feb 22, 2013 at 02:18 AM
RustyBug
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p.1 #14 · p.1 #14 · Please help to identify the problem!


Gotcha ... thanks.


Feb 22, 2013 at 02:42 AM
phuang3
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p.1 #15 · p.1 #15 · Please help to identify the problem!


Hi guys, sorry for the late reply. After I talked to my friend last night, he confirmed that it was 580EX for that particular session, not YN-560 which I stated before. (post updated)

cgardner,
Sample image has been resized with higher compression ratio. It should be faster to load. And, yes, he was shooting RAW. (not full RAW, but mRAW or sRAW) I will post the download link when I got it.

RustyBug,
Thanks for the analysis. I did the same thing on PS, and realized it was red channel's problem. At first, I was expecting that the red channel was completely gone (H/W error), but it turns out there are a few on the image. So, I don't know how to explain this.
Unfortunately, the purple one was deleted immediately. The green one is the second one that catches his eye, so he decides to keep it. According to him, the ambient light is sun light only, and it's very dim at that moment. 580EX was placed on the upper left triggered by YN-622C E-TTL remote trigger.

Keenyee,
He got one Sandisk 16G only. I wouldn't say it's impossible to see a faulty Sandisk, but the RAW file is intact and can be opened without problem. He never had this problem with this particular memory card though.

visualist & BrianO,
I will tell him to reformat the card, thanks. It also appears that his 7D has an older firmware. I already told him to do the firmware update.

As soon as I got the RAW files, I will update the thread. Again, thanks for the input.



Feb 22, 2013 at 05:41 AM
RustyBug
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p.1 #16 · p.1 #16 · Please help to identify the problem!


phuang3 wrote. According to him, the ambient light is sun light only, and it's very dim at that moment. 580EX was placed on the upper left triggered by YN-622C E-TTL remote trigger.


That's interesting.

Any chance the flash was aimed in such a way that the lens saw the flash directly (akin to a specular reflection) or is reflecting off the bodice and it yielded a very low/underpowered flash due to the ambient @ high ISO. This would leave a disproportionate need for ambient to provide exposure. If it was a dim cool light (cyanic/absent of red) that could account for the extreme lack of red, coupled with just a touch of contribution from the flash (ever so slightly warm). Curious if any of the RAW data can tell us at what power the flash was delivered?

Are there other pics from the same lighting setup?

Here's a link to a thread with a girl sitting in a white room.
http://www.fredmiranda.com/forum/topic/1132903/0#10816651

You can see how cyanic the ambient is in the shadows. This link is to one that is in a pretty bright ambient setting, but with a dimmer ambient, the cyanic cast could be even stronger ... just wondering if cyan + (barely) yellow = green that we are seeing. I know I'm "odd man out" on this, but underpowered flash allows ambient cast. We sometimes see this in rooms lit with tungsten and a weak flash (snaps usually) to give a magenta/purple cast, so it is plausible that we have a weak flash and cyanic ambient to give us a green.

The thing that's kinda got me stuck on the "underpowered flash" is the fact that with the (global) hue adjustment, it readily turned into what looks like an underexposed image in a room with tungsten lighting. If the data was truly absent, I don't think it would have been able to look as it does after the hue adjustment, and subsequent tweaks.

Even though the "purple" one wasn't retained, could you post up a normal image so we can see the proper colors in her dress/flowers/skin?



Feb 22, 2013 at 06:27 AM
alohadave
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p.1 #17 · p.1 #17 · Please help to identify the problem!


BrianO wrote:

Unless the shot was made under a green light, it's almost certain that the problem was the red and blue channels not being recorded properly. If all the shots were that way, it could be a sensor issue, but if it's only one in a hundred it's more likely somewhere in the I/O stream. Previous experience suggests to me that it's a card fault, although it could be in the camera.

Reformatting the card sometimes cures recording issues by unscrambling the file allocation structure. (When the card is scrambled, the three channels may not record to the same area, and one
...Show more

The card isn't going to kow anything about color channels. All it sees is a file and the file is already built when the camera goes to write the file.

And reformatting can fix the problem because the card controller writes bad block information into the card file table so that bad blocks don't get used. It's not about scrambling anything. The controller autmatically randomizes where it writes on the card to avoid using the same blocks over and over again.



Feb 22, 2013 at 01:35 PM
phuang3
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p.1 #18 · p.1 #18 · Please help to identify the problem!


Finally, I got the RAW file! Yoy may download it here.

It turns out the RAW file is ok, but the embedded JPG has problem. (He was shooting mRAW+JPG)
From the open file window I can see the green preview.

http://kspqm.kymco.com/ckfinder/resource/johnny/image/IMG_8584PS.jpg


After it was loaded into PS6, the camera raw decoded the image data correctly. (well, to some extent. WB is 50000k, and the tint is -150!)

http://kspqm.kymco.com/ckfinder/resource/johnny/image/IMG_8584PS2.jpg

It looks like a firmware bug on 7D!



Feb 22, 2013 at 02:07 PM
RustyBug
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p.1 #19 · p.1 #19 · Please help to identify the problem!


Amazing how much difference one extra little "0" can make (i.e. 50,000 vs. 5,000)

One click to change WB to "Cloudy"

I guess that makes about as compelling a case for shooting RAW as you could ask for.







Feb 22, 2013 at 03:08 PM
phuang3
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p.1 #20 · p.1 #20 · Please help to identify the problem!


RustyBug wrote:
Amazing how much difference one extra little "0" can make (i.e. 50,000 vs. 5,000)

One click to change WB to "Cloudy"

I guess that makes about as compelling a case for shooting RAW as you could ask for.



For no reason, WB is absolutely out of range (so is Tint), but what could cause this? I can only think of software bug.



Feb 23, 2013 at 01:16 AM





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