Home · Register · Software · Software · Join Upload & Sell

Moderated by: Fred Miranda
Username  

  New fredmiranda.com Mobile Site
  New Feature: SMS Notification alert
  New Feature: Buy & Sell Watchlist
  

FM Forums | Canon Forum | Join Upload & Sell

1      
2
       3       4       end
  

Noise in back-lit shots
  
 
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #1 · p.2 #1 · Noise in back-lit shots


In our Bayer array pattern we are using 4 pixels in the form of 1 Red, 2 Green, 1 Blue to achieve our composite information.

In situations where our lighting is not full spectrum, and we may be utilizing predominantly one color of light (say interior tungsten, for example), then we are only gathering information predominantly from the 1 Red pixel. This reduction in the amount of information we have collected creates a different amount of signal, and thus the noise is presented greater than expected. Similar reason why shadows (predominantly blue light), or some skies can render a more challenging noise pattern at higher ISO's (heavy reliance on only 1 Blue pixel without much aid from 2 Green pixels or 1 Red pixel).

This is in part why a subject illuminated with flash (i.e. vs. tungsten, etc.) will have less noise than one illuminated with "single color" lighting (even with each having proper exposure). Flash fill is often used for illumination purposes, but even a -FEC can offer gains in spectral response without blasting an overexposure onto your subject. In my slide film days, I used to dial my -FEC to around -1 1/3 or -1 2/3 for a kiss of spectral improvement without blasting my subject and losing the softer ambient quality.

In the case of the backlit window scenario ... depending on time of day / orientation, it may be that the light filling into the room (assuming the window IS also the light source for the room) is not full spectrum.

Typically, window light is chosen for its soft quality. The conditions needed for that "soft" quality are that direct sunlight is NOT coming through the window. Instead, it can be indirectly illuminated from the sky (vs. direct sun). In turn, the omission of direct sun (warm light) and reliance on sky light (cool light) places us in a scenario where we are NOT using full spectrum lighting. As such, we are reducing the amount of information that we have to work with for the full 4 pixel collection to something less.

Even though our exposure may be correct, the noise pattern can be different.

I experienced similar phenomenon while shooting some "warm light only" shots @ ISO 800 with a new camera. I was put off by the noise and returned the camera. Only later, did I come to realize it wasn't the camera, rather my nearly singular color lighting source that limited the amount of information I was collecting. Whereas ISO 800 in full spectrum lighting looked fine, ISO 800 did start to show unsavory noise in the lesser spectrum lighting conditions. A similar condition could be occurring with the "cool" lighting (or "warm" if the source light is the interior tungsten, etc.) ambient lighting.

As others have mentioned, a post or link to the image in question would certainly help us to better decipher your question. To a certain degree, I am hazarding a guess if your scenario fits into the model I've referenced ... so, yes an image would be helpful.

I get that you understand proper exposure for your subject (i.e. blown backlight is okay), and that this is not an issue of DR for you, but rather trying to understand the "what gives ", or "why could this be any different".

Again, a pic would help, but simply stated, full spectrum lighting will have less noise than partial spectrum lighting (ceteris paribus).

If you are going to shoot this regularly (you mentioned you like doing so), you may want to run some test shots giving an extra 1/3, 1/2, 2/3, 1, etc. stop of exposure as a means of collecting "more information" onto your "less pixels" checkerboard (i.e. Bayer array) to find out where it makes a diff in your noise pattern. I'm guessing you'll find 1/2 - 2/3 stop more exposure sufficient to aid your cause ... i.e. more light = more info, more info = less noise.

HTH




Nov 10, 2017 at 02:43 PM
dhphoto
Offline
• • • • • •
Upload & Sell: Off
p.2 #2 · p.2 #2 · Noise in back-lit shots


rek101 wrote:
No you babbled about something that didn't help me in any way. I wanted help, not someone's babbling.


Thanks for that, confirms my opinion that you're not worth bothering with. Blocked.



Nov 10, 2017 at 03:40 PM
TeamSpeed
Offline
• • • •
Upload & Sell: Off
p.2 #3 · p.2 #3 · Noise in back-lit shots


dhphoto wrote:
Thanks for that, confirms my opinion that you're not worth bothering with. Blocked.


Wow that was quite the response, I don't blame you. There is quite nothing like somebody asking for help, others trying to offer what they can without being provided examples, only to have that person come off like a know-it-all. Why open up a "Help Me" thread at all then?

I have no real issues getting shots of people with large windows/patios behind them if I don't care about blowing out the background. The only time is when there is artificial lights or partial spectrum, and even that doesn't pose a problem until I am in the higher ISO ranges. Oh well, not much more to add here on this thread without a raw file to look at...



Nov 10, 2017 at 04:09 PM
dhphoto
Offline
• • • • • •
Upload & Sell: Off
p.2 #4 · p.2 #4 · Noise in back-lit shots


TeamSpeed wrote:
Wow that was quite the response, I don't blame you. There is quite nothing like somebody asking for help, others trying to offer what they can without being provided examples, only to have that person come off like a know-it-all. Why open up a "Help Me" thread at all then?

I have no real issues getting shots of people with large windows/patios behind them if I don't care about blowing out the background. The only time is when there is artificial lights or partial spectrum, and even that doesn't pose a problem until I am in the higher ISO ranges.
...Show more

Thanks, sounds like the guy has no idea what he's doing, won't help by providing a file and is an arse. Best to let the thread die but that's not up to me.



Nov 10, 2017 at 04:21 PM
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #5 · p.2 #5 · Noise in back-lit shots


dhphoto wrote:
Thanks, sounds like the guy has no idea what he's doing, won't help by providing a file and is an arse. Best to let the thread die but that's not up to me.


I suspect he knows more than you are giving him credit for. It seems that while he may be reluctant to post an image (who knows why), he did present an honest question and tried (poor cyber-comm's a bit) to convey that DR / contrast wasn't his question.

Cyber-comms can be a tough gig, sometimes. You calling him an arse ... is not appropriate FM conduct. Sorry if you got your feelings hurt because he said you "babbled" in a non-helpful direction. Sure, he could have said, "Thanks, but that's not it." and it might have gone down smoother. Still, it is not him being an "arse" ... it is us not understanding (yup a pic could help) what he was trying to convey.

Good FM'ers don't go around calling folks an "arse" every time they get their feelings stepped on. Sometimes the newer members haven't quite learned how to communicate in the "FM" way (i.e. coming from other forums). Sometimes it behooves us to help them learn to better communicate in the "FM" way ... rather than pulling out the "he's an arse" so readily.



Nov 10, 2017 at 04:37 PM
dhphoto
Offline
• • • • • •
Upload & Sell: Off
p.2 #6 · p.2 #6 · Noise in back-lit shots


I don't feel the need to justify what I write, that's for the moderators to moderate if they feel the need. Not sure why they would in this instance.


Nov 10, 2017 at 04:54 PM
alundeb
Online
• • • • •
Upload & Sell: On
p.2 #7 · p.2 #7 · Noise in back-lit shots


I don't mean this personal, but one of the reasons FM is a good place is that there is a culture for good behaviour that is learned, and in fact little moderation.


Nov 10, 2017 at 05:01 PM
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #8 · p.2 #8 · Noise in back-lit shots


dhphoto wrote:
I don't feel the need to justify what I write, that's for the moderators to moderate if they feel the need. Not sure why they would in this instance.


Fred is not going to step in and moderate you calling someone an "arse" unless someone reports it first. Fred believes in minimal "censorship" from moderators. Rather, he believes that we should conduct ourselves with a proper decorum toward our fellow FM'ers, and that our seasoned and good fellow FM'ers should lead the way for modeling the decorum of FM ... which is the hallmark of what makes FM, FM.

All I'm saying is that calling another member an "arse" is ad hominem and unbecoming to the decorum of Fred's expectations. Hey, we all have our moments, but the direction and spirit of what Fred expects is not to go around calling each other names ... "arse" or otherwise.

As to "moderation", Fred prefers we tend to that ourselves via our individual self-moderation ... when that breaks down a bit, then as a group. When all else fails, then Fred will do what he needs to do. Yes, a single "arse" comment is not going to bring Fred onto the scene. But, I still believe it is not a comment that is deserved ... especially not coming from such a longstanding member of FM.



Nov 10, 2017 at 05:02 PM
Photonadave
Online
• • •
Upload & Sell: Off
p.2 #9 · p.2 #9 · Noise in back-lit shots


OK, moving on . . .

Here’s a question for the OP, is the severity of the noise the same with different lenses or is it more noticeable with one particular lens?

I ask as another possible cause that I ran across recently could be due to a lens issue and the post processing adjustments to correct for it.

In the past I’ve been noticing that my old 28-70mm f/2.8L had more overall glare & lowered contrast from windows in the background compared to other lenses. It seemed to be getting worse over time or maybe I just hadn’t noticing it before. Occasionally I would remove the lens and while looking through it at a white sheet of paper or wall in the background that I only noticed what I consider to be a small amount of dust inside not considering that to be the problem. I wrote it off to older tech optical design & coatings. After all similar newer version lenses were reported to have better control of reflections, flair & glair. I also noticed that when I processed these type of pictures that I would need to crank up the contrast and add a little more sharpening to get the pictures to look good. A notable downside of these more aggressive adjustments was that the overall noise was increased. In order to lift the contrast of the image content the noise was also lifted & made more noticeable!

Recently at an outside event at night with party lights strung overhead I noticed that my flash shots looked reasonably good, for using a flash, however the same shots with the flash turned off & other camera settings reset for the low available light with this one lens were low in contrast and exhibited a soft fog like halo/glow around the party light bulbs. Since there was no fog or haze of any kind visible in the air that night my first thought was that the lens needed cleaning. I inspected the lens in similar fashion as before however this time with small bright flashlight shining through from behind and found the problem. Some inner elements had a noticeable very smooth/fine haze in addition to the already familiar looking minor dust specks. In comparison all of my other lenses were crystal clear, no haze, with only minor dust visible if any.

Needless to say this lens will be going out for a cleaning.



Nov 10, 2017 at 05:08 PM
engardeknave
Offline
• •
Upload & Sell: On
p.2 #10 · p.2 #10 · Noise in back-lit shots


RustyBug wrote:
In situations where our lighting is not full spectrum, and we may be utilizing predominantly one color of light (say interior tungsten, for example), then we are only gathering information predominantly from the 1 Red pixel.


My mind is blown. Even though I know how sensors work, I had never made this connection.



Nov 10, 2017 at 05:47 PM
 

Search in Used Dept. 



AJSJones
Offline
• • • •
Upload & Sell: On
p.2 #11 · p.2 #11 · Noise in back-lit shots


RustyBug wrote:
Fred is not going to step in and moderate you calling someone an "arse" unless someone reports it first. Fred believes in minimal "censorship" from moderators. Rather, he believes that we should conduct ourselves with a proper decorum toward our fellow FM'ers, and that our seasoned and good fellow FM'ers should lead the way for modeling the decorum of FM ... which is the hallmark of what makes FM, FM.

All I'm saying is that calling another member an "arse" is ad hominem and unbecoming to the decorum of Fred's expectations. Hey, we all have our moments, but the direction and
...Show more

I agree with your description of Fred’s philosophy and how most FMers conduct themselves. I do, however, admit that I had a similar reaction to the OP’s description of a post, from an FMer who was trying to help, as “unhelpful babbling”.



Nov 10, 2017 at 06:32 PM
riokid
Offline
• • • • •
Upload & Sell: On
p.2 #12 · p.2 #12 · Noise in back-lit shots


I got a headache going through this thread especially the vehement opposition of the OP to provide a sample image the knowledgeable "elders" could work on



Nov 10, 2017 at 06:45 PM
AJSJones
Offline
• • • •
Upload & Sell: On
p.2 #13 · p.2 #13 · Noise in back-lit shots


engardeknave wrote:
My mind is blown. Even though I know how sensors work, I had never made this connection.


I had my mind blown a few years ago, once I started going back to old slides: some of them were shot indoors (tungsten lighting ) but on daylight film. Tried to fix the colour balance of a digital grab but there was no blue channel to speak of, only noise



Nov 10, 2017 at 07:04 PM
TeamSpeed
Offline
• • • •
Upload & Sell: Off
p.2 #14 · p.2 #14 · Noise in back-lit shots


The 2 issues I am sure are going on, since he doesn't want to share anything, are:

1) Underexposure - causing issues in post processing.
2) Glare if the light is directed more head-on causing loss of contrast due to the amount of strong lighting going directly across the frame inside the lens.

This was at 2 stops EC with the sun directly coming into the lens, causing flaring through the frame. Any other tests, where I tried to make sure I had good exposure, had no issues at all. It was only this situation that caused problems. If there are artificial lights as Rusty points out, not having a full spectrum will cause some issues, but mostly only if you don't set a correct WB, or you have a wide mix of light sources, making a white balance hard to obtain. I can shoot a concert with just colored spot lights at high ISO and not get that much noise, provided I set my WB correctly and I expose properly.

Very extreme case of back lighting where flare is causing most of the issue...



This is ISO 10K on a 7D2 for a concert where they had colored spot lights, so the noise is manageable in this very extreme case of not having full spectrum lighting.



ISO 12800 almost all blue... noise now due to high APS-C ISO


I am very comfortable stating that is simply poor selection of settings and WB that is causing the issues that prompted this post. but with examples, I could be proven wrong, and would be more than happy to accept that.



Nov 10, 2017 at 10:02 PM
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #15 · p.2 #15 · Noise in back-lit shots


AJSJones wrote:
I agree with your description of Fred’s philosophy and how most FMers conduct themselves. I do, however, admit that I had a similar reaction to the OP’s description of a post, from an FMer who was trying to help, as “unhelpful babbling”.


+1 that the OP didn't help his cause with the "babbling" remark ... as I previously mentioned.

Sadly, the OP is likely going to be MIA now that we've resorted to accuse him of trolling and calling him an "arse". I mean, if someone accused us trolling and called us an "arse" ... how long do you think we'd stick around.

Besides, the "babbling" comment came AFTER he was accused of acting like a TROLL.

Only to be followed up with the assessment of the OP being an "arse" after his "babbling" response following being accused of trolling.

Put the shoe on the other foot, and see how it fits ... probably not anything we'd like either. Just sayin'.



Nov 11, 2017 at 04:50 AM
OntheRez
Offline
• • • •
Upload & Sell: On
p.2 #16 · p.2 #16 · Noise in back-lit shots


Weird that someone wants help but won't provide an example so this forum can attempt to provide information.

Best I can tell - from Teamspeed's post - we're looking at a light spectrum beyond the camera's ability to capture. I don't remember the small light/dark range of a camera vs the human eye.

I approach the problem in two ways. First is to shoot the best "average" I can and correct in post. (Often only sort of OK.) I've also had success with a 3-shot HDR and processing without any of the HDR madness.

I think we're dealing with a limitation in our tools. It's likely to take a new sensor/paradigm to expand DR.



Nov 11, 2017 at 04:50 PM
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #17 · p.2 #17 · Noise in back-lit shots


I don't think the OP is asking about anything related to DR at all. He is asking about why a properly exposed (yes, blown blacklit BG outside the DR of the sensor) subject (illuminated by NOT the backlighting directly) has more noise than when using a flash to illuminate the subject with a similar proper expsoure.

Everyone wants to jump on the DR issue, and that is not his question at all (from what I can tell).

rek101 wrote:
Well if I spot meter on the face and expose it correctly, the window is of course blown out which is what I wanted. What I didn't understand is why the face is still very grainy.


Imo, the issue at hand is related not to the matter of the DR being exceeded in the backlighting. Rather, the issue rests in the lighting that IS illuminating the subject. Of course, without an image to deconstruct the lighting, we really don't KNOW what that lighting is. So, as such we have to accept the concept that the OP has exposed it correctly (as he so indicated above), rather than jump on the bandwagon of telling him that he is doing something wrong.

It strikes me that his awareness of the situation and use of spot metering is indicative of someone who does in fact have a degree of credence to the matter. Yet, for some reason he is experiencing something that differs from when he illuminates the subject otherwise. Accepting that "exposed it correctly" stands as stated regarding the QUANTITY of light, then we have to consider what possible differences there might otherwise be. COLOR of light, CONTRAST level of light (specular / diffuse), thus remain as viable attributes.

Typically, a backlit situation conjures up the prospect of underexposure (i.e. fooled metering). Here however, we have the OP stating that he is spot metering the subject (i.e. to avoid metering error from the backlighting), and presuming to also avoid an underexposure (i.e. exposure is correct).

Like everyone else, I would like to see the images so we can more assuredly assess the deconstruction. But, without the images, we are reliant on what the OP has written. However, it seems that some folks were quick to dismiss (or just glossed over) the viability of what he wrote as pertinent information.

Cyber-comms can be a tough gig sometimes.

I just find it unfortunate that folks are assessing the character of the OP simply because he hasn't provided an image. It isn't like he is the first person to have reasons why they don't want to post an image. Granted, most of us are very proficient with doing so, so it seems to be a normal tendency / expectation. But, even so that doesn't make someone a troll or an "arse" for not doing so ... particularly after being told he was doing something wrong and not being listened to for what he was trying to further explain.

Quite simply, he may have not know how to post up an image in FM ... yet, no one bothered to offer up to him the various ways in which he could have done so (i.e. before calling him a troll and an arse). It could also be that the images were not authorized for public display. Or, even that he has already deleted images, or ...

I mean, I recall a time that I was a member of FM ... and had not yet learned of the different ways to post images to FM. Did that make me a troll or an arse? Okay, maybe I shouldn't ask that.

Suffice to say, I think that Page 1 is far too soon to be accusing someone of trolling and calling them names to denigrate their character (top of Page 2), just because the cyber-comms weren't going according to the norm.



Nov 11, 2017 at 05:35 PM
dhphoto
Offline
• • • • • •
Upload & Sell: Off
p.2 #18 · p.2 #18 · Noise in back-lit shots


For the avoidance of any doubt, I used the words I used because I meant them and have no wish to retract anything.

I showed the OP nothing but support and advice and he started calling names. He/she proceeded to troll. If you guys can't spot a troll you need your eyes testing.

I'm disappointed that certain members here have such thin skins and want to point-score, but perhaps that what FM has sadly become.

I don't post here much nowadays because there are too many people with whom I do not see eye to eye, it's just not worth it, which is a shame as I've been here a long time. Such is life and the internet, time to do some hiding of people



Nov 11, 2017 at 07:16 PM
RustyBug
Offline
• • • • • •
Upload & Sell: On
p.2 #19 · p.2 #19 · Noise in back-lit shots


Sorry, but I seem to have missed where the OP was calling names. However, I do see where he said "thanks" a couple times ... ummm, before the trolling assertion was presented.

Just like I missed where the OP was calling names, I missed where he was trolling and I missed where he was being an "arse".

Just because the OP continued to seek a different answer from the ones given ... is that the definition of a troll. If it is, then I certainly qualify as a troll by that definition. Lord knows I have my times when I can't get folks to understand what I'm asking for / talking about. Yet, nobody ever accuses me of trolling or calls me an "arse" just because I might be struggling with the cyber-comms.

Just sayin' ...

Not everyone is so well versed that we are always on the same page right away. Sometimes it takes a bit to get there. Imo, the troll / "arse" call was premature. That, and even if the OP was trolling, the "arse" statement was still inappropriate by Fred's expectations, imo.

YMMV






Nov 11, 2017 at 07:28 PM
TeamSpeed
Offline
• • • •
Upload & Sell: Off
p.2 #20 · p.2 #20 · Noise in back-lit shots


When somebody tries to help you and asks for a file, and you tell that person they just aren't being helpful and babbling, and you don't want to hear their babbling, how is that not being an dweeb, jerk, or whatever other favorite noun? At this point, it is over, the person isn't going to help themselves any by supplying a file.


Nov 11, 2017 at 11:25 PM
1      
2
       3       4       end






FM Forums | Canon Forum | Join Upload & Sell

1      
2
       3       4       end
    
 

You are not logged in. Login or Register

Username     Reset password