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Craig Zuckerman avatar image
Craig Zuckerman asked ·

DOF and "fireflies"

Hi, can someone please give me a good range of samples to use in a render,? the part of my model that is out of focus has grain, also, in my IPR, my image is 72 dpi, do I need to change settings for out put of 300 dpi, for example,? thank you

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Mike Farnsworth avatar image
Mike Farnsworth answered ·

The only way to resolve DOF noise is to use more AA samples. The actual number of pixel samples in Arnold is the square of that number, however, so don't go too crazy with it. (AA samples of 4 means 16 pixel samples, AA samples of 5 means 25 pixel samples, etc.) This is because doubling the sample setting will get you roughly half the amount of noise, which is intuitive. However, it will take four times as long.

You often can get away with reducing the other sample settings as you increase AA samples; e.g. AA samples of 1 and GI diffuse samples of 5 is roughly equivalent in indirect diffuse noise as having AA samples of 5 and GI diffuse samples of 1. Because you need to increase your AA samples to deal with DOF noise, you can probably decrease your other sample settings (lights, GI samples) to compensate so that your render time doesn't go up a lot.

Also for DPI, Arnold knows nothing about it. If you want a 300 DPI image in the same size, you need to render out of Arnold at a higher resolution so that you have enough pixel data. For example, if you had 1920x1080 image, at 72 DPI that would fit an area of 26.67 in by 15 in (1920/72 by 1080/72). But if output that same image at 300 DPI, it would only take 6.4 in by 3.6 in (1920/300 by 1080/300). So, if you needed an image at least 12 in wide and 16:9 ratio, you would need 12*300 = 3600 pixels wide and 3600*9/16 = 2025 pixels high.

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Craig Zuckerman avatar image
Craig Zuckerman answered ·

Hi, I was just reviewing the great advice concerning , removal of fireflies, yes the rayswitch node is great , but the suggestion is, to lower the specular weight to zero, fireflies are gone, but my model is devoid of highlights; can someone please explain why the specular weight needs to be at zero, and as an experiment, I raised the specular weight to .2 while using the ray switch, some highlights come back , perhaps I should try, increasing spec. roughness, in crease light size? any insight would be very helpful, thank you -PS, what if I use distant light, and not a quad, can't reduce size, or can I

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Craig Zuckerman answered ·

Thank you Lee, CZ

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Lee Griggs avatar image
Lee Griggs answered ·

That's a very small intensely bright specular. You could try increasing Specular Roughness or increase the light size. More tutorials about removing noise can be found here.

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Craig Zuckerman avatar image
Craig Zuckerman answered ·

Hi Mike,how are you,? please see attached render. In this piece, I did increase the AA, but also used ray switch, and reduced the specular weight in all models, but I still get the fireflies; are there any other solutions, or do I just resign myself to retouching in Photoshop. Please let know, any revelations, would be awesome, Craigantibody-lipids.jpg


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Craig Zuckerman answered ·

thank you

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