Noise problem

[k_meade]

<p>I am a beginner with digital photography and did my first outdoor photoshoot with my nephew a couple weeks ago, but I feel like I got some inconsistent results that I can't explain. It was an on-and-off cloudy day using only natural light. Many of the pictures not only have noticeable noise, but there is a weird discoloration in the edge of some of the shadow/highlight areas (purplish and gray in some places). I know that some of them are underexposed, but I didn't think that amount of underexposure would create so much noise.<br>

Even with ISO 800 and being a little underexposed, I am still surprised by the amount of noise. Do you think it's simply because of the ISO and exposure that it has this much noise, or is there something else at play that I'm not thinking about that would cause this. Not all the pictures had this, but many of them did, even when I was the one taking the picture. I tried to upload an example, but it looked completely different after uploading than it does on my PC.</p>

<p> </p>

[k_meade]

<p>I should also add that I had a B+W polarizing filter on my 24-105mm f1.4L lens and have a Canon 6D. I should have removed the filter, but I had it on because it had been previously raining, and I wanted to reduce the glare from the greenery. I'm just wondering if the filter had something to do with it.</p>

[William Michael]

<blockquote>

<p>It was an on-and-off cloudy day using only natural light. Many of the pictures not only have noticeable noise, but there is a weird discoloration in the edge of some of the shadow/highlight areas <strong><em>(purplish and gray in some places)</em></strong>. I know that <strong><em>some of them are underexposed</em></strong>, but I didn't think that amount of underexposure would create so much noise. . . .<strong><em>Do you think it's simply because of the ISO and exposure that it has this much noise, . . .? </em></strong></p>

</blockquote>

<p>Probably, yes.</p>

<p>Generally underexposure will exacerbate the appearance of noise, especially at High ISO. Even ½ to 1 Stop underexposure can be noticeable as “more noisy” than the correctly exposed image.<br />You can test this yourself by making a Bracket of 5 shots in 1 stop increments of any scene and use an High ISO – an indoors scene is very useful to make this test..</p>

<p><a href="/photo/17144492&size=lg">If this is an example of the problem you have:</a> <br />I note that you made this shot at: F/8 @ 1/100s @ISO800.<br />Working backwards, that would be a “correct” exposure for a scene with EV10 (exposure value / light value).<br />EV 10, when outdoors, can be described as “heavy overcast shade” or “very deep shade” or “at sunset light not in direct light”<br />So, if your exposure for that shot is incorrect, I don’t think it is very much incorrect, but it could be enough to cause you to notice the extra noise.</p>

<p>***</p>

<blockquote>

<p>I tried to upload an example, but it looked completely different after uploading than it does on my PC.</p>

</blockquote>

<p>I don’t perceive an enormous amount of noise apparent, in that particular sample image.<br />I expect that in the uploading, or your preparation for uploading <strong><em>the image was modified</em></strong> – therefore the noise might not be as noticeable when we look at the image in your portfolio.<br />The sample image has a BLUE cast. This common when shooting in OPEN SHADE, but can also be an indicator of the image being a touch UNDEREXPOSED.<br />Also, my guess is that your PC probably doesn’t have the monitor calibrated – so the colours (the Blue Cast) that I see on my calibrated Monitor, very likely is not exactly what you see.</p>

<p>Also - FYI the sample is soft on the face of the Subject – that would likely be because of couple of elements, or a combination of both:</p>

<ol>

<li>a small movement (Camera and/or Subject) and the Shutter Speed not fast enough to counter.</li>

<li>didn’t nail focus.</li>

</ol>

<p>WW</p>

<p>Addendum - I can't see how the Filter would add to noise</p>

[JosvanEekelen]

<p>Can you post pictures? Overall picture + detail</p>

[jcuknz]

<p>Noise comes from amplification of the signal so throwing away 1.5 stops of light with the filter could contribute to making noise not from the filter itself but from the resultant extra amplifcation. <br>

I would like to know what camera mode you were using and how the camera was set-up to cause the under-exposure. We should get such info from the EXIF of a photo you post so ensure your editing process doesn't strip it off if you want real help rather than guesswork.</p>

<p>After you post your contribution the programme here at PN takes you a page where you can browse your computer to find the file you want to add. You need to resize the image to no more than 700 pixels across and/or vertical and with a file size of less than 100Kb for the image to show with the message. Note also the need for a caption to be entered on that page. If you want to show detail, such as noise, then make a 100% crop to those specifications. <br>

For a digital newbie I would mention that it is usual and normal for DSLR images to be sharpened unlike P&S cameras which probably do it for us 'in-camera' unless we turn it off.</p>

[dcstep]

<p>ETTR ("expose to the right") with digital, to minimize noise. Generally, in overcast conditions, shooting in Raw, you'll want +1EV, or more. Shooting JPEGs, you'll still want +1/3EV. </p>

<p>If you're having to raise overall levels in Raw conversion, then your under exposing. The only reason to underexpose is to save important highlight. If you get into that situation, HDR is the best solution to expose for both shadow and highlight with minimal noise. Of course, if the subject is moving, then multi-exposure HDR is a problem.</p>

[k_meade]

<p>It sounds like it may just be the fact that it was underexposed that there seemed to be extra noise. Again, I thought being the 6D that it could stand a bit of underexposure. I looked at many of the other images that seemed correctly exposed, and I didn't notice any apparent noise like there was in the the darker ones.<br>

The photo that I posted on photo.net was, in fact, one of the ones that I was talking about; however, it doesn't look like it did before I uploaded it. Both in RAW, TIFF in photoshop, and jpeg in PS, it was much brighter and had apparent noise. As for calibrating my monitor, I tried to do it last night, but I'm not sure if I did it correctly. I actually did see the blue cast that someone was talking about, but that only appeared after uploading it. I shot in RAW, imported it in LR4, rendered/edited in PS CS4 as a TIFF, then I saved it as a JPEG so that I could upload it (for the record, besides the cropping in LR4, I did no processing on the one I uploaded so that you could see it as shot). The color of that picture changed completely after uploading it (his blue shirt looks more purple).<br>

As for how it was shot, I had my camera in manual mode. That particular picture was shot by my dad though because I was actually in it (I cropped it due to not know if my nephew wanted a bunch of pictures posted on the internet, so half a face was a compromise in my mind). My dad's 73 and used manual focus, so that's probably why it was definitely soft (I set the aperture to f8 instead of f4 because I wasn't sure how he would do with focusing).<br>

I guess I just need to practice more getting the correct exposure and metering (and learn how to use the histogram). Using manual mode, it seemed that the meter bar fluctuated a lot even without moving the camera that much left/right. If I'm doing portraits, would you recommend that I use spot metering? Thanks.</p>

[William Michael]

<blockquote>

<p>If I'm doing portraits, would you recommend that I use spot metering?</p>

</blockquote>

<p>If you choose to use Spot Metering for available light shooting (and I use Spot metering mostly always) - it is very important to understand the various tones that will be in any scene and have a very good idea which ones approximate Photographic Grey - <strong>does that make sense?</strong><br>

The camera's meter is looking for about 12% to18% "Photographic Grey".<br>

So IF for example you spot meter on my face (which is un-suntanned Caucasian skin) you would get different reading than metering off a Dark Skinned, Person's Face.<br>

Knowing these facets, is one of the critical elements of using use Spot Metering efficiently and ‘correctly’ for any Available Light shot: this is so one can assess what areas are to be exposed ‘perfectly’ and make the appropriate meter readings on various parts of the scene and then lock the exposure at what you deem to be "correct".</p>

<p>WW</p>

 

[dcstep]

<p>Metering off the face with spot is a way to go, particularly if the BG is very dark or bright in comparison. As William said in a different way, you meter off a light face, then you might end up underexposed because the meter is exposing for a medium grey. Ideally, you'll have you medium grey photo card with you and have your model hold it next to the face to get both a meter reading and color balance. On the fly, you'll have to get a feel for how the various metering patterns of the camera will work.</p>

<p>If you get to know the metering patterns well enough, you can apply plus or minus EV as you look at the scene. Center weighted is really useful for me when doing head shots.</p>

<p>No matter what, ETTR. Next time you hand the camera to your old man, take the polarizing filter off. ;-)</p>

[William Michael]

<p>Yes, exactly.<br>

Depending upon what you spot meter, the light meter might give you an inappropriate result.<br>

What I was getting at specifically - <strong><em>is to know how much to correct</em></strong>, for different tones which you might be metering in the scene.<br>

For example, if, using my cameras I were to meter off lightish Caucasion skin, I would open up about 1½ Stops.<br>

If I were to meter off a White Shirt or Dress, I would open up about 2 Stops.<br>

If I were to meter off typical green foliage (in the same light as the Subject’s face) then I would not adjust.</p>

<p>Yes, definitely a Grey Card can be very useful if you want to use spot metering: but you can also learn to see the tones, especially to recognise and learn by rote, different skin tones, if you want to spot metering off Subject’s faces. <br>

<br>

WW</p>

 

[dcstep]

<p>I think that William and I agree that spot metering is really an "expert" technique for those that really understand the Grey Card and how meters on digital cameras try to push an pull the exposure in a what that's not intuitive to most noob users.</p>

<p>I really like the Center Weighted metering. Review the manual and take careful note of the patterns of the various metering options. All that said, you still have to ETTR when shooting digital, unless you insist on shooting in-camera JPEGs, then you'd expose as if you're shooting positive film.</p>

[jcuknz]

<p>Surely whether you use spot or centre weighted the key to the situation is an appreciation of what is going on so you the photographer can take what the meter tells you with a grain of salt or not and decide what you want. <br>

PS ... there is nothing to stop you using a centre weighted meter as a spot meter when the situation requires it ... you just have to walk up close.</p>

[dcstep]

<p>This is the "Beginner" Forum, so I don't think that we should assume that the OP will have any appreciation for how things like DSLR meters actually work. I know that I was caught out by an incorrect assumption about how the meter was working.</p>

[William Michael]

<p>Specifically about <strong>TTL Metering</strong> (Through The Lens Metering):</p>

<p>It is my view that a basic understanding of HOW each Metering Mode works and subsequently understanding HOW that affects the final image in VARIOUS shooting scenarios are cornerstones to good quality Available Light Photography.</p>

<p>Also I hold the view that “ETTR” (Expose to the Right) and “Check the Histogram” and “Watch the Blinkies” – are useful techniques to know and understand: but NONE is more important than understanding HOW each metering mode works – the main reason is, that if an understanding of the metering mode is attained, then the Photographer has the advantage of making a shot, confidently, and without necessarily needing to ‘review and correct’. It is obvious that I am skewed to this thinking because my background is making Photographs where “review and correct” was not usually an option.</p>

<p>In these regards I agree that Spot Metering is more ‘expert’ (‘expert’, purposely in inverted commas) and that using Spot Metering correctly and more importantly, USEFULLY, necessitates not only understanding how the TTL Meter works, but also the nuances of TONE in a scene (which I’ve mentioned above.)</p>

<p>So what I would suggest to any beginner (or experienced Photographer if they haven’t done so) is to really knuckle down and get to grips with how each of the Metring Modes works, in their camera(s).</p>

<p>***</p>

<p>It is important to recognize that different camera manufacturers may use slightly different names for the Metering Modes. As we are discussing CANON DSLRs on this thread – I’ll make the point that whilst using CWA (Centre Weighted Average) metering AND moving in close can used as a facsimile for Spot Metering - if one is using a Canon DSLR, then using Partial Metering Mode, is better for that task, because one does not necessarily need to “move in close”. </p>

<p>WW </p>