Grainy Pictures

[ksalsgiver]

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!! 

[RobertTheFat]

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.

[ksalsgiver]

Hi Bob,

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

[oldsurfer]

Try using ISO 100 and a camera support!

[TCampbell]

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.

[ksalsgiver]

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! 

[amfoto1]

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 
 

[ScottyP]

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.

[ksalsgiver]

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!

[ebiggs1]

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.