07-30-2015 02:01 PM
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!!
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07-30-2015 02:17 PM
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.
07-30-2015 05:11 PM - edited 07-30-2015 05:13 PM
Here's your meta-data from the grainy image:
07-30-2015 07:59 PM
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.
07-30-2015 08:52 PM - edited 07-30-2015 08:56 PM
07-30-2015 10:02 PM
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.
07-30-2015 12:16 AM
07-30-2015 12:18 AM