7D High ISO Noise & Auto ISO Questions...

<p>I took some pictures at my friends wedding a couple weeks ago. There was no professional photographer and I wanted to help them document the event. </p>

<p>I was shooting a Canon 7D with an EF-S 18-55, (my Xsi kit lens), in AV mode with the aperture set to F/8 and the ISO set to AUTO. <br>

I attached an example picture that has been converted from the RAW file with no adjustments being made, other than the exposure was raised +1.0 because it was underexposed.</p>

<p>My first question is why my camera would have picked such a high ISO, (3200), as the room was well lit with a huge window and lots of sun coming through a thin, white curtain. I didn't even think to check the ISO, (which is a lesson I wont ever forget), because I assumed in such a bright room it would be fine. I suppose it is possible that I had the ISO set at 3200 by accident, but I really remember setting it to AUTO and just leaving it there, (which is what I usually do). Any other reasons the ISO might have been so high? As another point of reference, I was also using a Lumix LX-3, and in the same room with the ISO set at 400 and the aperture F/4, it produced a great exposure, (although somewhat noisy which I would expect from that camera).</p>

<p>My second question has to do with the noise in the picture I attached from the 7D. The picture seems REALLY noisy to me, as do all the others taken in this room at 3200 ISO, (AUTO). These pictures are REALLY noisy, especially if you zoom in or crop them at all. One of the reasons I upgraded from my Xsi was for the ability to shoot at higher ISO. I am just wondering if there is something going on with my camera or if this is the kind of noise you would expect from a 7D at 3200 ISO? </p>

<p>Thanks from a noob.</p>

<p>Dan</p><div></div>

<p>First, The picture would be under exposed due to the white background.</p>

<p>Second, The picture is noisy because you raised the exposure artificially by 1 stop.</p>

<p>Solution ,You should have increased the exposure compensation in the camera during shooting. Then use bigger lens opening .</p>

<p>Btw, what is the shutter speed in this exposure?</p>

<p>Hi Dan, auto ISO can be extremely useful, but you do need to keep an eye on the shutter that you're achieving (if in aperture priority). If auto ISO is picking a setting that affords you a faster shutter than you really need, then you can manually set the ISO lower to gain an edge on noise.</p>

<p>For example you're in AV, auto ISO, and you're shooting a more or less static subject at 100mm focal length. If auto ISO is picking say, 1600 ISO, and the resulting shutter is 1/250th, you can likely manually set the ISO to 800 and still have a fast enough shutter.</p>

<p>As far as noise in this photo, doesn't look too bad, but I believe you that it probably looks worse at full size. Beyond the fact that bumping the exposure in post will make already noisy images much noisier, your goal of lower noise by switching from Rebel XSI to 7D is perhaps going to disappoint you, as they have basically the same SNR across the ISO range that they share.</p>

<p>http://www.dxomark.com/index.php/en/Camera-Sensor/Compare-sensors/%28appareil1%29/619|0/%28appareil2%29/185|0/%28onglet%29/0/%28brand%29/Canon/%28brand2%29/Canon</p>

<p>Granted the 7D has a higher top end, but sites like Photozone that do stringent testing of sensors are not too positive about 7d high ISO performance. Photozone says 1600 ISO "may still be useable at times." That's not a glowing endorsement.</p>

<p>Personally my advice is that for a shot like this you should have been using a flash, bouncing it off the walls and/or ceiling. Not only would you have much lower noise, but likely better color and tone.</p>

<p>Shutter speed is 1/40th of a second, lens is zoomed all the way to 55mm.</p>

<p>I didnt know that raising the exposure in post processing results in higher noise. I thought it was considered a good, (conservative?), thing to slightly underexpose, then fix in camera RAW...?<br>

I am a little confused about your solution... I understand I could have increased exposure compensation, EV value), to brighten up the picture. I also could have metered it differently to get the same result, correct? But chossing a bigger lens opening in AV mode would have just resulted in a faster shutter speed and had no effect other than DOF, ... or am I missing something?</p>

<p>Oh I see it now, The exif file says that you have f8, 1/40 speed and -0.7 in camera compensation at 55mm of the kitlens and AV mode.</p>

<p>The biggest mistake here is the -0.7 exposure compensation.</p>

<p>If it were me I'd just use P mode and auto iso, With 0 compensation, An under exposed iso 3200 image would look alot noisier than a properly exposed one. But that's just me, I hope more people that are more experienced that I am, Would chime in their thoughts and settings for this matter.</p>

<blockquote>

<p>I thought it was considered a good, (conservative?), thing to slightly underexpose, then fix in camera RAW...?</p>

</blockquote>

<p>No, other way around. The higher the exposure the better the signal to noise ratio</p>

<blockquote>

<p>I understand I could have increased exposure compensation, EV value), to brighten up the picture. I also could have metered it differently to get the same result, correct? But chossing a bigger lens opening in AV mode would have just resulted in a faster shutter speed and had no effect other than DOF, ...</p>

<p>or am I missing something?</p>

</blockquote>

<p>Yes, it would have also given you a lower ISO, if you'd dialed the shutter back down, or opened the lens up. Again though, this should have been flashed. The light was too funky in any case. Flash, done right, would have given you much better color, and negated the noise/ISO issue.</p>

<p>Brett: What you said in your first paragraph makes alot of sense, and I will be sure to keep an eye on my shutter speed and ISO in the future!<br>

But why would my camera have picked 3200 ISO in the first place?<br>

And your info about the relation to high ISO noise between the Rebel and 7D surprises me. I read the 7D review on photo.net and it said that, "At ISO 1600 and 3200 noise is still quite low but at 6400 it starts to become objectionable," and, "Overall, I’d say that the 7D has the best noise performance of any Canon APS-C sensor camera to date."<br>

Thank you for your advise on a flash. I NEVER even think of my flash, mostly because I have no real idea on how to use it. And I thought I would get better color and tone with natural light as opposed to flash...<br>

I obviously have alot of learning to do.</p>

<blockquote>

<p>But why would my camera have picked 3200 ISO in the first place?</p>

</blockquote>

<p>Auto ISO is generally smart but isn't perfect. In your case it was actually generous in only picking 3200 given that your shutter speed was slower than your focal length.</p>

<blockquote>

<p>Thank you for your advise on a flash. I NEVER even think of my flash, mostly because I have no real idea on how to use it. And I thought I would get better color and tone with natural light as opposed to flash...<br /> I obviously have alot of learning to do.</p>

</blockquote>

<p>Bounced flash can work very well for images like this. The walls and ceiling provide a huge surface to scatter and diffuse the light of the flash, so you get all the benefits of full illumination, accurate color, low noise, etc. without the harsh shadows or flat, washed out look that aiming the flash right at their faces would produce.</p>

<p>Conceivably you could have gotten good color with this natural light, but it looks like funky mixed light. To me it has the typical pinkish. washed out look of a shot that probably should have been flashed. The choice of flash vs. not is a personal one, but in the heat of the moment you need to take some shots in the available light, using the best settings and technique you can, and see if the results are attractive. Then do the same with flash and decide which route to go. Otherwise you can spend a lot of time at your even getting subpar shots when a change in technique would produce much better results.</p>

<p>Thanks Brett. And off-topic, your photo's are inspiring and amazing. I just spent a few minutes perusing your website. What I wouldn't do for your eye!</p>

<p>I tried auto ISO for a short while and, while it was okay 2/3 of the time, about 1/3 of the time it picked a crazy high ISO. You can't really trust it if you're picky about IQ. So I turned it off and dial it in myself. With that said, 7D auto ISO is much better than 40D auto ISO, so it's slowly improving.</p>

<p>And, like others have said, large areas of white or light colors will fool any meter as it expects an average distribution of tones. And weddings, snow and white sand beaches are typical places you need to override the meter by adding +.5 to 2.0 EV depending on the situation. And I agree a burst of fill flash would have helped the couple "pop" and controlled the contrast.</p>

<p>Dan, I'm not smart enough to be able to interpret graphs or other data suggesting the 7d isn't much different than the Xsi at higher ISOs, but having a lot of prior experience with a Xsi and 6 months with a 7d under my belt, I'll unequivocally state the 7d is clearly cleaner above ISO800. It isn't even close in my book. I have borrowed my friend's 5d2 and believe the high ISO difference between that camera and the 7d is much closer than 7d vs Xsi.<br>

I've had satisfactory results up to ISO5000, generally by overexposing a full stop and backing down in Aperture.<br>

I would not hesitate to use ISO1600 in any circumstance.</p>

<p>The camera picked ISO 3200 in an effort to make the shutter speed faster. The room was fairly bright for interior but there's really no such thing as a well-lit room, at least for photographic purposes. You'd forced f/8, you were zoomed out to 55mm so the camera probably wanted a shutter speed of 1/80 to keep the camera shake blur to a minimum. So it ramped the ISO up to 3200, and even that only got it to 1/40. In short, it did what it was supposed to do.</p>

<p>The scene is difficult because it's strongly backlit, and that does tend to throw off the meter; and your -0.7 stop exposure bias is actually pushing the exposure the wrong direction. (Though, that bias did make the shutter faster and so might have prevented camera shake from ruining the photo completely... at least this way you got something.)</p>

<p>Easiest thing to do would have been to use f/5.6 instead of f/8. And in the future get a fast lens if you want better shots in these situations. A 50mm f/1.8 would easily have handled this without boosting the ISO to crazy levels.</p>

<p>Thanks everyone for your input. I learned alot of things from this experience including:</p>

<p>1) ALWAYS check your ISO when in AUTO,<br>

2) I should tend to overexpose, then dial back in post-processing,<br>

3) Time to start experimenting with flash.</p>

<p>5d2 has much better noise, relatively, at high ISO. 7d and newer rebels are all using essentially the same sensor. The big jumps come between point and shoots and aps-c dslrs, and between apc-dslrs and full frame models like the 5d2. It just comes down to engineering realities.</p>

<p><img src="http://www.brettcolephotography.com/client_files/pn/pic.jpg" alt="" width="630" height="352" /></p>

<p>Yeah what needed to happen is one of two things. This shot needed to either be exposed correctly so that the noise would be less noticeable. OR you could easily just not shot at a constant f8.0 in this shot. this shot could have been done at half that or more depending on the focal length used and what your smallest aperture number is, all while keeping the individuals in focus. So lets just say you were shooting this shot at say f/4. You are letting a MORE light into the sensor than you were at f/8, so you can then effectively shoot the same exposure as you did above with a 1600 iso instead. <br>

As mentioned, the 7d does well with iso but you want to have an overexposed shot before having an underexposed shot. When you edit a high iso image that is underexposed and try to bring up the exposure after the fact, you are introducing more noise to the image. If it was overexposed, you can reduce the exposure some and the noise is less noticeable I have taken some usable images at 12,800 iso with that camera. Would i print them super big? probably not. But still very usable. its really about your exposure and also the use of some noise reduction. Also, high iso shots can look very nice in black and white (black and whites look great depending on the shot) as the high iso gives a film grain look and the color noise is not a factor (still produces "grain" in a black and white, but does not visually show the color pixels you see in the color shot). So you can always give a black and white conversion a try and see how the image looks.<br>

I never shoot iso auto...there is just too little control there. If shooting in Av mode which i do, alongside of manual, i set my iso based on the lighting conditions, adjust my aperture a little as needed for the type of focus (depth of field) and lighting needed and just make sure that my shutter is reasonable. All this means is that if i am indoors in similar lighting, i might get my iso to 800, 1600, 3200 if needed...and stay there until the lighting changes a lot ( i go outside, by a window, etc...) and so all i am worried about is making sure my aperture is what i want which is what you are already doing when you shoot, and making sure i have an acceptable shutter for the image i am trying to capture. This method will be a good idea to use so you don't have iso shooting thru the roof on you when you can control it by adjusting other settings.</p>

<p>With regard to high ISO on the 7D, you might also check to see what the in-camera noise reduction is set on. I generally have mine set at the standard setting and get great results shooting at 3200ISO, while still retaining detail. I find the noise performance to be a lot better than the 30D I used to have and the 40D I now use for a back-up camera.</p>

<p>I don't shoot weddings--I did one years ago, and that once was enough stress for me--but I would offer a couple of suggestions.</p>

<p>First, yes, learn to use flash. When the background is lighter than the subjects, and you lack good lighting on the faces, flash is the way to go. If you want to avoid fancy equipment, get yourself a stofen omnibounce, maybe $15, and a Demb Flip-It, which is maybe $25 or $30. Bounce the flash, and use the flip-it to get some reflected light on the faces. For a really nice introduction to flash--both how it works, and how to use it--check out:</p>

 

<h1 >Speedlights & Speedlites: Creative Flash Photography at the Speed of Light [Paperback]</h1>

<p> <a id="contributorNameTriggerB001HCZFDW" href="http://www.amazon.com/Lou-Jones/e/B001HCZFDW/ref=ntt_athr_dp_pel_1">Lou Jones</a></p>

<p>Second, turn off auto ISO. The more automatic stuff you turn on, the less control you have. Set the ISO at a tolerable level. Then it will be obvious to you if you are running low on light--the meter will call for too slow a shutter speed. You can then bump up ISO and deal with the noise, or get more light.</p>

<p>Thanks again to everyone who responded and gave advise.</p>

<p>Dan M's advice is key. Bounce flash will completely change your results for the better for this kind of photography. The difference is dramatic. You do need a dedicated external flash though. At a bare minimum the Canon 270 is only $140. It doesn't rotate though, it only tilts up. The 400 and 500 series flashes give you full control.</p>

<p>The 7D chose ISO 3200 because no matter how bright the room appeared to your human eye, at f/8 there wasn't very much light reaching the sensor. The camera had to choose 3200 to get a 1/40s shutter speed, which is already dangerously slow for a subject which moves and that focal length, regardless of IS.</p>

<p>Because you had underexposure dialed in and the subject is darker overall than middle gray, the noise in the subject is effectively worse than what you would see from a properly exposed ISO 6400 shot. (I'm betting your Lumix shot had the advantage of the subjects being lit from the front. Just because you're in the same room doesn't mean the exposure is the same every direction you point. It can be radically different with just a few degrees of movement.)</p>

<p>Contrary to several of the responses, this is not evidence of poor high ISO performance on the part of the 7D or APS-C bodies in general. A properly exposed and processed ISO 3200 7D shot will make 11x14 and 13x19 prints with low visible noise. I've got ISO 2000 7D prints that show tighter grain than ISO 160 and 400 35mm portrait films show. Those were standard wedding films for years and continue to be used by some wedding photographers to this day. This is a far cry from "may still be usable at times." (Read the Imaging Resource print evaluations for a better perspective on what can be accomplished at each ISO.) Also, a 7D will show less noise in print than a XSi regardless of per pixel SNR measurements for the simple fact that the pixels are magnified less from the 7D for any given print size. So yes, it is a step up in regard to high ISO, though probably not a huge step.</p>

<p>That said, APS-C in general does not tolerate underexposure well at high ISO, at least not compared to the FF bodies. And that's true of the 7D specifically. You increased exposure in post by a stop and the subject still looks dark. You desperately needed some fill light to balance out the bright background. The subject is basically more than a stop underexposed.</p>

<p>Suggestions?</p>

<p>* Buy and use faster glass. A 50 f/1.4 could have given a proper exposure at ISO 800 assuming f/2.8 for some DoF. You can easily make quality 24" prints at that ISO from a 7D.</p>

<p>* Use bounce flash in situations like that.</p>

<p>* Do not use auto ISO. Meter your scene, know what's needed, and make your own choices about the settings. (I'm not against Tv or Av, but when you add auto ISO it becomes too easy for the camera to indulge bad aperture and shutter choices. Your eye is more sensitive than any DSLR sensor. Rooms that are well lit and bright to you are not necessarily so to a camera.)</p>

<p>Daniel, you are right, now that I look back at them, the Lumix shots where from the exact opposite direction and where front lit!</p>

<p>I'm not a fan of auto ISO. It seems to pick a higher ISO than I think it should. For instance, I can be outside in bright light and the camera will pick ISO 200. Ive taken shots at that ISO, then drop it to 100 and the camera performs well. <br>

Brett is spot on with the bouncing flash. I'm not really good with a flash, but when I have experimented with bouncing flash, it amazes me how it improves the shot without blowing out the subject. I just need to use it more.<br>

Brett, thanks for that link. I have an XSI and was contemplating upgrading to a 7D, assuming it will have better ISO performance. Me thinks I should spend the $$ on better lenses. </p>

<p>Dan<br>

As others have suggested Auto ISO has let you down. In my experience the 7D is very sensitive to exposure at high ISO. It is the first APS-C body I have owned as all my others are full frame or APS-H but it does seem more sensitive to exposure errors when shooting at high ISO. I find that mine is quite usable at ISO 1600 and can be used with care at ISO 3200. The difference between the 7D and say my 5DII is that you can get away with a lot of exposure issues at ISO 3200 on the 5DII and still get a good image. On the 7D I find I need to be within 1/3 of a stop of a perfect exposure and even then process quite carefully. The new metering system on the 7D is actually an improvement in backlight performance as it looks at the colours of the image. Unfortunately for those of us who have got used to the evaluative Canon metering system over the last 20+ years the 7D generally needs less exposure compensation than you expect.<br>

If you are shooting weddings I suggest that you do it the old way with the camera in a semi-auto mode such as Aperture priority and set the ISO and aperture to settings that give you the depth of field you are looking for and a reasonable shutter speed. Then if you find that you have to use high ISO you are aware of the need to nail the exposure. DSLRs make checking your exposure very simple - set the camera so that it shows the histogram and the smaller image after the shot and just look at the histogram. If the histogram shows spikes at either end you will immediately be aware you need to correct your exposure. You can also set the camera to flash the areas that are under or over exposed so that you do not blow highlights or lose shadow detail. In the case of your image yo have obviously blown the highlights on the wall behind the guy. Even if the exposure settings and noise were more controlled these blown hilights ruin the shot as they pull the eye towards them.</p>

<p>The overall problem was not enough light on the sensor. The shot was underexposed about 1.5 stops, making it effectively about ISO 8000. Properly exposed with a wider aperture -- I feel f/4 or even f/2.8 should have been adequate -- could have delivered a shot at ISO 800 to 1200. Image stabilization and a slight assist from a monopod might bring that even lower, while still keeping shutter speed high enough for slow moving subjects.</p>

<p>Also, the 7D is diffraction limited at f/7.2, due to its very fine pixel pitch. f/8 was sub-optimal for the shot.</p>

<p>Existing light can be challenging, as others have pointed out. Dim interiors is one problem. Contrast range is very often an issue with average room lighting. Even outdoors especially in direct sun, contrast range is a problem. Flash often goes a long way toward solving all three, but might not always be available or even appropriate. The real solution is to shoot lots in various kinds of light. It helps to practice and experiment before having to do it under pressure.</p>

 

<p>Brett: You say-<br>

"5d2 has much better noise, relatively, at high ISO. "<br>

Your graph @ ISO 3200 showed this:<br>

26.0db/5D2 24.5db/7d<br>

"Much better"?<br>

1.5db.<br>

Really?<br>

I'd say- "marginally"<br>

rt</p>