topic Re: Grainy Pictures in EOS DSLR & Mirrorless Cameras

Grainy Pictures

ksalsgiver — Thu, 30 Jul 2015 18:01:16 GMT

Hello,

We are pretty new to using a Canon camera and lens. We are currently using Rebel T5i and the lens that I am having problems with is EFS 18-55mm f/3.5-5.6 IS STM. When the camera is on the tripod my pictures are fine, but if I am hand holding the camera the pictures turn out grainy. I change the shutter speed when I am hand holding it. Any ideas on why this could be? Here is a picture of the grainy when I hand hold the camera, and non grainy when it is on the tripod. Any help we can get is much appreicated!!

Re: Grainy Pictures

RobertTheFat — Thu, 30 Jul 2015 18:17:01 GMT

You're probably using auto-ISO. The higher shutter speed on the handheld shots forces a higher ISO setting, which increases the noise level. The noise ("grain") consists of false positive responses to the incoming stream of photons, caused by the higher gain being applied to the sensor.

Re: Grainy Pictures

ksalsgiver — Thu, 30 Jul 2015 18:23:50 GMT

Hi Bob,

My ISO is set on 12800 should I change that to something different?

Re: Grainy Pictures

oldsurfer — Thu, 30 Jul 2015 20:35:41 GMT

Try using ISO 100 and a camera support!

Re: Grainy Pictures

TCampbell — Thu, 30 Jul 2015 21:13:41 GMT

Here's your meta-data from the grainy image:

Camera: Canon EOS REBEL T5i

Lens: EF-S18-55mm f/3.5-5.6 IS STM Shot at 43 mm

Exposure: Auto exposure, Aperture priority AE, 1/125 sec, f/22, ISO 12800, Compensation: +5/3

Flash: Off, Did not fire

Date: July 30, 2015 12:43:35AM

Color Space: sRGB

Software: Adobe Photoshop Lightroom 5.7 (Windows)

Field Of View: 29.6 deg

File: 1,193 × 2,812 JPEG (3.4 megapixels) , 683 kilobytes)

I've highlighted some items in red -- to call attention to these.

The ISO needs to come way down.... this is the primary reason for the image being so grainy. If the camera is not moving and the subject is not moving then you have all the time you need to take an exposure. There's no need for ISO 12800 in a situation like this. ISO 12800 is for situations when you're desperate, you must get a shot, and you'd rather have a grainy shot than no shot at all or a blurry shot.

The second shot was taken at ISO 200... which is 6 stops down. The shutter speed is .4 seconds (nearly 6 stops longer (0.5 would have been exactly 6 stops longer) which means the camera traded ISO for shutter speed.

But I also notice f/22... and that's forcing the camera to find other ways to gather light (either through long exposures or via very high ISO settings). This is happening becuase you chose Aperutre priority mode (Av) and then selected an aperture of f/22. f/22 is a very tiny aperture opening.

I also noticed that your reflection shows up in the link bracelets. This is because shiny jewelry acts like a mirror. Rotating the watch to a bit of an angle will help.

ISO 100 has virtually no "noise" in an image. ISO 200 & 400 are also very low (almost no noise). At ISO 800 you'll probably notice some noise, but it's manageable. At ISO 1600 you'll see a bit more, and at ISO 3200 even more still. ISO 6400 will have a lot of noise and ISO 12800 is so noisy that it's basically unusable. The lower the ISO, the lower the noise.

Re: Grainy Pictures

amfoto1 — Thu, 30 Jul 2015 23:59:52 GMT

The very "grainy" image is showing image "noise" from using a very high ISO... 12800. That was necessary to get a correct exposure due to your lens aperture (f22, very small) and your shutter speed (1/125) to be able to hand hold the shot, plus you have 1-2/3 + exposure comensation dialed in.

The image without grain was shot using a tripod and a much slower shutter speed (1/3 second), the same super small aperture (f22), and the same + 1-2/3 exposure compensation, but using ISO 200 instead. This was possible because of the much slower shutter speed and tripod.

Both images were shot in Aperture Priority (Av) mode, which is auto exposure where you select the aperture and ISO, and the camera then chooses an appropriate shutter speed based upon those (and the + 1-2/3 EC you have dialed in).

For one thing, try not to use such a small aperture. There is an optical effect called "diffraction" that reduces fine detail when such small apertures are used. The second (not grainy) image is showing some evidence of diffraction. Notice how it looks a little "soft"? Try to use f8 or f11 for sharper images. The only problem with using a larger aperture is that it will reduce depth of field, especially when shooting close ups like this where there is litte DoF anyway. Bigger apertures mean shallower DoF. Longer focal lengths and closer subjects also mean shallower DoF. If this is a problem shooting these subjects, you might try a process called "focus stacking", where several images are combined using the sharp portions of each, in order to increase apparent DoF.

You have two choices when it comes to the issue of too high ISO and the image noise that results. You can either make longer exposures, which probably will require putting the camera on a tripod and might also mean locking up the mirror to prevent internal camera vibrations (which also can be done using Live View, if you prefer). Or, you can add light with strobes, flashes or continuous lighting of some sort. This will be tricky with reflective jewelry. Often a "tent" is used for this purpose... that acts to diffuse the light all around the subject.

You also are getting "self-portrait" reflections in the shiny polished surface, most obvious in the wrist band links in the second shot. You also see some lighting above and behind you being relected there. You may be able to minimize the self-portraits by making a black "flag" with a hole in it for your lens, that you and the rest of the camera are hidden behind. Another way to avoid those sorts of reflections is to use a Tilt Shift lens, that shifts to one side to "dodge" the self-portrait reflections.

Jewelry is a particularly tricky subject to shoot. This just scratches the surface. You might look for some books and tutorials on the subject, that can give you lots more info and ideas.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
FLICKR & EXPOSUREMANAGER

Re: Grainy Pictures

ScottyP — Fri, 31 Jul 2015 00:56:12 GMT

I don't know how you ended up pinched down to f/22. That made necessary the nose-bleeding lay high ISO which in turn gives you the grain. Your camera does ISO 200 great. Stick to that.

You are shooting a still subject. That gives you an incredible advantage IF you use a tripod. You could do practically as long an exposure as you need for even poor room light because there is no subject motion blur or camera shake blur to worry about.

Re: Grainy Pictures

ebiggs1 — Fri, 31 Jul 2015 02:02:31 GMT

Hmm, ... the last three posters must not have read the first two, one by Bob from Boston and one by oldsurfer. Who correctly identified your problem of too high ISO.

What happens is simular to your audio stero system. The camera (stero) has an amp in it. Both increase the signal either a video or a audio electronic waveform. However, like your stero you get distortion as volume gets louder. Aslo like your stero there is a low volume threshold. No dostortion but no sound either. That is ISO below 100. Usually ISO 100 is the "cleanest" setting you can use. Of course this is a much simplified explaination but you get the drift? Both are an electronic device.

Re: Grainy Pictures

ScottyP — Fri, 31 Jul 2015 04:16:33 GMT

Only Biggs would have the cheek to chime in at the end of a string of all similar agreeing answers, with the same message, but to open with a statement that the folks ahead of him were all being redundant. Truly the kingdom of Cheek has a king, and his name is Biggs.

Re: Grainy Pictures

ScottyP — Fri, 31 Jul 2015 04:18:19 GMT

🙂

Re: Grainy Pictures

ksalsgiver — Fri, 31 Jul 2015 12:58:52 GMT

That makes a lot of sense thank you so much for the help!! Like I said before we know some but very very little about this kind of camera. Very much appreciated!

Re: Grainy Pictures

ksalsgiver — Fri, 31 Jul 2015 13:16:15 GMT

Alan

I just tried what you said and WOW did that help out a lot!! Thank you for putting it into step by step for us! Also The pictures that I posted were just taken very quickly to show the grain, we usually make it to where the reflection is not there lol!! But thank you for the help with that as well!

Re: Grainy Pictures

TCampbell — Fri, 31 Jul 2015 13:40:36 GMT

You can find numerous videos on photographing shiny metal objects.

Here's a video that will help you with the basics: http://youtu.be/C8HNBcu3Hig

The watch dial is a bit different because you want to eliminate the reflection from the crystal but still see the face below. That usually calls for a circular polarizing filter to reduce the reflections.

Re: Grainy Pictures

ilonkagray — Tue, 07 Aug 2018 19:04:45 GMT

Hello

I recently bought asecond-hand Canon 5D Mark 111

I have been shooting children at schools in AV format, but resulting in grainy images. So i thought, clearly im getting my ISO wrong within the AV setting. (Usually ISO 800 inside classrooms, and ISO 400 outside in playgrounds - f4)

So i put ISO on AUTO. But i still am getting grainy images, as per the attached. In fact, the grain in the image attached was worse in its original raw size (19 meg) - looking a little better in its small 2meg size actually.

What am i doing wrong do you think? Surely the camera is clever enough to get this right?

ilonka

Re: Grainy Pictures

kvbarkley — Tue, 07 Aug 2018 19:10:02 GMT

That looks fine to me. Ken Rockwell shows that grain is pretty well controlled even at high ISO's:

https://kenrockwell.com/canon/5d-mk-iii.htm

You should probably start your own topic and attach a crop.

Re: Grainy Pictures

ebiggs1 — Wed, 08 Aug 2018 14:07:00 GMT

A couple things. Yous shot is slightly underexposed to my liking. That will show more grain. In general it is a good looking shot so I would not be concerned, just a 1/2 stop more exposure.

This is how you shot it if you were wondering because it isn't as you suggested.

f8, 1/40, ISO 1250 and FL of 32mm. MPO is I never use auto ISO. Never! That is P&S stuff if you want a P&S you don't need a 5D3. Set your ISO where you wnt it.

Using f8 and 1/40 I am pleased you got as good a shot as you did.

Re: Grainy Pictures

ilonkagray — Wed, 08 Aug 2018 17:16:09 GMT

Hello

thank you for your feedback.

Youre absolutely right, that was the AUTO measurements.

I reverted back to controlling my ISO today, going lower than ever. Whilst better , sadly i am still seeing some grain.

Somehow i am not achieving the clarity im looking for.

Thanks for the feedback anyway.

ilonka

Re: Grainy Pictures

ilonkagray — Tue, 14 Aug 2018 12:18:43 GMT

I am still achieving grainy images 😞

I noticed a '!" onscreen when looking through my viewfinder. Could this be the cause?

Any thoughts?

Re: Grainy Pictures

ebiggs1 — Tue, 14 Aug 2018 14:09:04 GMT

"I noticed a '!" onscreen when looking through my viewfinder."

My cameras don't have that but I think it means it can't achieve focus. Your shots look pretty normal. Slight underexposure but I think they are OK.

Re: Grainy Pictures

TCampbell — Tue, 14 Aug 2018 15:08:58 GMT

This is a change of subject since the original thread ... it’s often better to just create a new thread.

Anyway, in the image you posted, I am not seeing any noise ... which makes me wonder what you’re seeing. I am specifically looking at the sock in the lower left corer (since that’s basically a black area). If the image is noisy... that area should reveal it. But I’m not seeing it in this image (possibly due to resizing).

Re-sizing an image to a smaller size involves reducing more pixels into fewer pixels. E.g. if you make an image half as wide and half as high, then that means each 2x2 cluster of pixels (4 pixels) will be reduced to just one pixel. If ONE of those 4 pixels was excessively noisy it will get averaged out by the other three non-noisy pixels and this naturally reduces the noise.

To truly evaluate the noise, we’d need to see a full-size version of the image (preferably the RAW “.CR2” file since JPEG images are typically auto-processed to reduce noise.

So a bit about noise...

ALL cameras have noise. But the reason you might see one image and think it has no noise and see another image and think it has a lot of noise has to do with something called the “Signal to Noise Ratio” (SNR).

Basically the noise level remains somewhat constant... but it’s the signal level that varies. If you don’t collect enough “signal” (good data) then the ratio is worse and you perceive a noisy image.

Exposure is based on ONLY shutter time and aperture size. ISO is not part of “exposure” because ISO is an amplification of the data which occurs only after the shutter closes and the image is captured. At that point any amplification is amplifying everything ... good signal and noise alike.

This is why people feel shots taken at low ISO don’t have noise and high ISO do have noise. The reality is that the amount of noise is the same. But in the low ISO shot, you either had more available light (good signal was arriving in abundance) or you allowed a larger aperture or longer exposure time until the camera collected enough signal... such that there was no reason to amplify the data. That results in a high amount of signal relative to the noise (a good SNR) so the noise isn’t amplified and you don’t perceive it (even though it really is there ... every digital sensor has noise.)

If you were to leave the lens cap on and take the fastest possible exposure at base ISO (ISO 100), then inspect the pixels in that “black” photo (since you would have guaranteed no light could enter the camera), you’d find the pixel values aren’t actually zeros... there very low values just fractionally above 0. This is because in order to operate the sensor, it has to be powered up (voltage must be applied) and there’s a minimum charge that can be read out from each pixel as a result. This is called the “bias” level. Also, you’d notice that the pixels wont all have the same value.

When the camera performs a read-out of the sensor, it collects “read noise”, there is also “thermal noise”, there’s even quantum noise (which can’t be eliminated ... it’s in the nature of the universe).

There are many kinds of noise that collect... but in order to not notice the noise you need to collect enough “signal” that the signal (good data) overwhelms the noise so that the noise simply isn’t noticed.

Enough on “why” you have noise (you can find loads of technical articles on noise if you want to know more). Once you have It, you can still do things in post-processing to reduce it.

”noise” is basically a pixel that reads a slightly higher value than it’s neighbors. This really tends to be noticed in dark shadowy areas... and also in smooth non-contrasty areas. It tends to not be noticed in bright areas and is more difficult to pick out in areas with lots of details (it can get camofauged in the detail).

The process of de-noising involves sampling neighboring pixels and then averaging the colors. But in areas of an image with high detail, this can result in the image starting to look soft. BTW, sharpening is the opposite... this involves finding subtle differences in contrast... and amplifying those differences. Since a “noisy” pixel is already different in contrast, when you “sharpen” an image you will increase the perceived noise.

So to deal with this, use tools that let you selectively sharpen only the areas you care about (e.g. eyes for example) and you can selectively de-noise the smooth areas.

There are de-noising tools that will deal with noise by tonal frequency (since noise tends to be stronger in shadow areas). But you can also build edge-masks so that you avoid de-noising edges that need to remain sharp... then invert the mask to sharpen only those edges without sharpening noise in the flat areas.