ISO, Noise, And Dynamic Range On Fujifilm With Examples/Downloads

#fujifilm #fuji #xt4 #fuji3514 #ISO #Noise #dynamicrange

Hello, I was recently spending a lot of time wondering about dynamic range and noise when it comes to the ISO setting on my X-T4. Since Christmas 2021 I have almost always shot my camera at ISO640. I was shooting pictures of the family and noticed that the window behind my brother and sister-in-law was blown out in the photos I was taking. I thought about it in the moment and realized that in video when you shoot in a LOG mode the ISO on my camera at the time is limited on the low end to 640, and that it's like that because that would be the native ISO and have the most dynamic range. This has to do with the science of our a sensor actually captures images. There's an amazing video by Filmmaker IQ that goes over all of this in amazing detail. I changed from 160 to 640 and literally saw the window gain detail as I raised the ISO(with shutter speed set to auto). It literally blew me away. From then on I only ever wanted to shoot at 640 to capture the most out of every image. But there were draw backs that I noticed. Noise is definitely more noticeable, and if you want to raise your shadows, or your shot is underexposed then you have issues with more noise and color distortion. I shot a lot at the lowest ISO I could shoot at before making this discovery, and those shots are so clean and sharp. Made me wonder if there was a happy medium or if maybe I was wrong. I then made up this quick test to see what is really going on and what the best choice would be. The premise is that shooting at 640 gives the most dynamic range over all, if shooting at a lower ISO do you get similar results if you underexpose? So what I did was place my gray card on a table in a back room which has big windows in the background and took a few of photos at different settings. I will shoot at two ISO setting 160, and 640. These ISOs are exactly two stops apart.

All of these examples can be downloaded. ISO 160, SS 160, f1.4: 0 exposure on the gray card

Shooting at an ideal exposure at the base native ISO

ISO 640, SS 640, f1.4: 0 exposure on the gray card

Shooting at an ideal exposure at the native ISO

ISO 160, SS 640, f1.4: -2 exposure on the gray card

Shooting underexposed to bring the highlights down

ISO 640, SS 2500, f1.4: -2 exposure on the gray card

Shooting underexposed to bring the highlights down.

Right out of the gate thoughts.

These photos make sense. In both shots, 160 and 640, the windows are just as blown out and the cats are super cute. BUT, Here's what happens when we lower the exposure by 2 stops of both images.

ISO 160, SS 160, f1.4: 0 exposure on the gray card -2 in Lightroom

ISO 640, SS 640, f1.4: 0 exposure on the gray card -2 in Lightroom

There's not a huge difference in these photos but you can see that in the ISO160 image that the building out side the window, the fence, and sky are blown out whereas in the ISO640 they aren't.

There definitely are more stops of dynamic range above middle gray when at ISO640. With my experience shooting and with some other tests that had some changing light so I didn't include them in this article, I could clearly see that there are about exactly 2 more stops above middle gray at ISO640 than ISO160. But lets take a look if we under expose the image and then bring it up in post.

ISO 160, SS 640, f1.4: -2 exposure on the gray card +2 In Lightroom

ISO 640, SS 2500, f1.4: -2 exposure on the gray card +2 In Lightroom

They both look pretty similar but if you look down in the shadows, even at full size you can see more noise and a discoloration.

ISO 160, SS 640, f1.4: -2 exposure on the gray card +2 In Lightroom Crop

ISO 640, SS 2500, f1.4: -2 exposure on the gray card +2 In Lightroom Crop

At the higher ISO we can see less detail, and more noise and discoloration. The thoughts that I have after looking through these photos is that it's not necessarily that the higher ISO setting has more dynamic range as much as it is that there are 2 stops more dynamic range above middle gray then at the base native ISO, and 2 more under at the base native ISO. Though with that said there still is information below middle gray just like in the native base but it's just not clean. Unlike on the other side where clipped is clipped and there's nothing you can do to bring it back.

My take away is that when I'm shooting in a high contrast scene I'll shoot at ISO640 to save as much highlights as possible. If it's not very contrasted then I'll shoot at ISO160 to get the cleanest image. Of course you could also just shoot at ISO160 and under expose the image as necessary with high contrast scenes. I'm less likely to do that because the image is great at ISO640, and also I don't have to worry about dark images in the preview and/or having to keep that in mind and adjusting for it. Plus I am a wedding/engagement/portrait photographer, being able to show clients their photos on the spot is helpful. If the previews are dark then they might question what I'm doing. Not that my clients don't trust me but that I don't think the marginal difference is worth the extra effort. With things like landscapes, nature, or special shots you'll want to have the best and cleanest image then it'll be worth it.

I think of the difference between these two photos. The one on the left was taken at ISO160 years ago for my brother and now sister-in-laws engagement session with my X-H1. And the one on the right was a month ago at ISO640 with my X-T4.

In hindsight I could've shot the photo on the right at ISO160 underexposed and then brought it up for the shadows to be a little cleaner. But ultimately with that set I used grain in Lightroom anyway to give this gallery texture so it didn't matter. Plus it's a battle between ease of shooting and the little difference in results.

I think that you can take this with a grain of salt. If this changes the way you shoot or makes you want to investigate it yourself then power to you. Maybe, like me you now want to choose the right ISO setting for your lighting/scene then that's also dope.

I really appreciate you and your time reading this. I hope this has helped you in some way.