Filters and Grainy images

[Vagebond]

Originally Posted by dcclark

... Canon has some equivalent to Nikon's ADR, which "enhances" shadows and generally pretends to improve the dynamic range of their sensors ... It's possible that that's what's causing the noise -- since your subject's face was in shadow, the camera may have bumped up the ISO for that area only, causing noise.

On my Canon 450D it's called "Auto lighting optimizer" and it's ON by default. Found under Custom functions. According to the manual it can indeed cause noise.

[dcclark]

Originally Posted by Vagebond

On my Canon 450D it's called "Auto lighting optimizer" and it's ON by default. Found under Custom functions. According to the manual it can indeed cause noise.

In that case, I'd bet money that this is the OP's problem!

(...not MUCH money, mind you, but I'd toss in some pocket change at least.)

[rickp1]

Excuse my ignorance, but you're saying the light optimizer could cause this?? So I should disable it?

Thanks
R.

[dcclark]

Do this:

1. Leave everything as-is. Take a sample photo (for example, another portrait) which has some bright sunlight AND shadows.

2. Turn the lighting optimizer off and take the SAME photo.

Compare them. If you can find noise in one and not in the other, then you have your solution!

It may also have settings for "Strength" or something -- you could turn it down a bit.

[rickp1]

LOL!!! but it's easier to ask others!!!!! LOL

Seriously now, you're right, I'll give that a try. The reason I ask is because I still haven't developed the "eye" to see what people with a lot more experience see, so a lot of times I miss things. But there no better way to learn than by doing.

Thanks
R.

[Dreadnought]

looks more like a focus issue rather than a ISO or noise issue to me...

[inkista]

Noise always shows up more in underexposed areas than in well exposed ones. Faces in shadow from the hat brims are going to be underexposed compared to, say, the shoulders that are in the sunshine. If you look at the shoulder area, there's no noise. If you look at the shadow on the face, there is.

When you use post-processing of any kind, to lighten a darker area (i.e., adjusting exposure upwards) digitally, you will be further increasing the noise. Canon doesn't selectively swap the ISO around on bits of the frame--the whole frame is taken with the same voltage gain across the sensor for light sensitivity. But the "lighting optimizer" does the equivalent thing that doing reverse-S curve in Photoshop does: brings up the shadows, brings down the highlights.

This "bringing up the shadows" bit is what's increasing the noise. If you were to shoot with lighting optimizer off, and then hand adjust in post to brighten up the faces, you'd get the same effect.

Fill flash, or being content with dark shadows across the faces, is pretty much going to be your only way to eliminate the noise.

BTW, when you underexpose something and bring it up in post-processing you're doing the digital equivalent of "push processing" and increasing the ISO. And this is how the cameras achieve the H1 and H2 levels of iso (6400 and 12800). Physically, the sensor only really goes to 3200 iso. That's why the noise performance is so bad at these "pushed" levels. AND it's also how some of the third-stop ISO settings are done. So, you could actually be getting worse noise with, say, iso 320, than you would with iso 400.

What everybody forgets to tell you is that it works the other way 'round, too. If you slightly overexpose something and bring it down (darken it) in processing, you'll reduce the noise. And pull processing is how the other one-third ISO settings are done. (I.e., to get iso 125, they may be pushing the iso 100 by a third stop, and iso 160 may be pulling 200 by a third stop).

This was definitely a bone of contention on the 5DMkI, since both of the 1/3 settings were done by pushing. So you'd actually have less shadow noise with iso 200 than you would with iso 125 or 160. With the 40D, Canon "fixed" things by doing push for +1/3EV and pull for -1/3EV of the full iso settings.

But this is why I turn off the 1/3 stop ISO settings in my 50D. I can't keep straight which one is going to add noise and which one's going to reduce it, so I just use the actual settings that are native on the sensor.