To Diffuse or Not?

[jbb]

I routinely shoot at ISO 800, with excellent results.
Bill

yes but that all depends on whether you have a point and shoot, micro 4/3 or dslr. A curious question, is it better to bump up the iso to properly expose a scene (low natural light) or capture said scene at a lower iso and adjust in processing? Six of one and half a dozen of another?

 

[Storker]

is it better to bump up the iso to properly expose a scene (low natural light) or capture said scene at a lower iso and adjust in processing?

Yes and no. Depends on the sensor.

Many of the recent dSLR models have an "ISO free" sensor, i.e. it doesn't matter whether you expose correctly at a high ISO setting, or underexpose at the native sensitivity. AFAIK, not all have, and older dSLRs don't have that kind sensors. For a non-"ISO free" sensor, pushing an underexposed shot in post will give more noise than upping the ISO and exposing correctly. With my dSLR, which doesn't have an "ISO free" sensor, I like to "expose to the right" (ETTR), i.e. overexposing slightly - while, of course, making sure not to blow out the highlights - and pull the image in post. That makes for a slight improvement in noise, particularly in the shadows. See Digital Exposure Techniques for some info on the ETTR trick.

And no matter your ISO setting preferences, personally I'd rather have a somewhat noisy, but sharp image, than an image with motion blur or unacceptably low DOF. If I can accept blur, I might as well add it in post, by using heavy noise reduction

 

[PatW]

I find that without diffusers, I get harsher shadows. I would agree that silvery fish work better with diffusers. If you have a powerful strobe, I would think that the loss of light would be less but I have not tested it. I have read that if you are really goodat adjusting your strobes so that anything closer to the lens is outside of the cone of light, that you get less Backscatter without diffusers. I am not that confident that I can control my strobes placement that well.

 

[jbb]

Yes and no. Depends on the sensor.

Many of the recent dSLR models have an "ISO free" sensor, i.e. it doesn't matter whether you expose correctly at a high ISO setting, or underexpose at the native sensitivity. AFAIK, not all have, and older dSLRs don't have that kind sensors. For a non-"ISO free" sensor, pushing an underexposed shot in post will give more noise than upping the ISO and exposing correctly. With my dSLR, which doesn't have an "ISO free" sensor, I like to "expose to the right" (ETTR), i.e. overexposing slightly - while, of course, making sure not to blow out the highlights - and pull the image in post. That makes for a slight improvement in noise, particularly in the shadows. See Digital Exposure Techniques for some info on the ETTR trick.

And no matter your ISO setting preferences, personally I'd rather have a somewhat noisy, but sharp image, than an image with motion blur or unacceptably low DOF. If I can accept blur, I might as well add it in post, by using heavy noise reduction

thanks, I have an Oly EM-5. BTW Digital Photography has started a series of articles describing sources of noise which at my first quick read supports your approach. I've never taken the diffusers off my two z240 strobes. I think the light would be too hard on the macro critters i am usually shooting.

What's that noise? Shedding some light on the sources of noise: Digital Photography Review