ISO - Digital Pull

Summer

I'm just getting into cameras again--for painting. I have a Canon Rebel T3 EOS 1100D. I'm mainly wanting to know if it is true about this “digital pull” thing and if I can use the concept on my camera. My native ISO settings are 100, 200, 400, 800, 1600, 3200. The magic digital pull settings on a better camera are 160, 320, 640, 1250, 2500, 5000. Since I don't have these magic numbers on my camera to play with, I want to try something else. Can I just reduce the ISO setting by one-third of a stop to achieve the benefit of the digital pull to the sensor to get the least amount of noise/grain? Like from 200 to 100? I prefer to add the noise/grain in my photo-editing software if I need it. I understand that all of the noise/grain can't be removed from the raw file once it's there. However, after having thought about it, this might change the dynamic range of light to dark intensities. There is something about this theory that doesn't set well with me. Why would I set up my shot in manual mode then deliberately move my ISO setting down a notch and throw everything off? Have any of you camera buffs heard of this? Thank you.

Summer

Excellent advice. Thank you. Good checklist to carry with me or keep on my desktop. It's all there! I may have to ignore this digital pull on the sensor thing because it doesn't set well with me on the camera I have--not enough ISO setting options. Maybe in another life.

[Deleted User]

I don't know about this digital pull thing either. Googling leads me to a different thing entirely (only applicable to video, not still images). It's definitely not something to concern yourself with though, otherwise I would have heard about it before. Like Kingston said, keep the ISO at the lowest you can without compromising aperture and shutter speed. If you NEED a higher ISO, use it — you're not going to paint the noise so it's only an annoyance. If your ISO is excessively high (and what amounts to excessive will depend on the camera) then you need more light or use a tripod or… obviously some shots are just not attainable with current technology! But don't get overly technical about it, photography is difficult but at the same time it's actually not very complicated.

Plus everything else Kingston said. ESPECIALLY ABOUT SHOOTING RAW.

Summer

Thanks, David. I have to keep reminding myself that I'm a painter and not a photographer. I will take your advice and not get overly technical about it.

rgr

I'm a geek at heart but not a photographer, so I'll just chime in and say a bit about this that I'm learning on the geek side of this. Namely that ISO on a digital camera is not the same thing as film speed. It's an approximation of that, and a relative indication of total light gathered over the surface area of the sensor in the camera. (film speed is a measure of film density per square inch of paper under a constant emulsion -- and in chemical photography you can modify the emulsion to modify your results. digital photography you're stuck with what the sensor recorded, modulo any post processing you can do in photoshop/lightroom.)

Also, just as with aperture and focal length, ISO scales with crop factor, but since surface area is an geometric measurement (power of 2), you need to scale ISO with the square of the crop factor. (e.g. a micro 4/3 camera has a crop factor of 2, so the best ISO you can achieve on most 4/3 cameras is ISO 100 and roughly equivalent to 400 ISO on a full frame sensor camera . ISO 200 is roughly equivalent to ISO 800 on a full frame camera, and so on.)

This is a little technical and not that important. Just remember that the bigger the sensor, the more light you get to keep, and the better results you'll get in less than perfect lighting. This is especially important if you print large prints. If you have a poor camera (e.g. with a very small sensor), shooting in RAW isn't going to help with this, though it will help you get the most out of what ever your camera did happen to capture.

Summer

@David_Quinn_Carder @Kingston @rgr Thanks for all the great information here. I'm sure that I will use this thread for future reference as time goes on. For now, what I shall do then is shoot with good lighting, use a grey card for reference, and make the photos look even better in Photoshop. Thanks everyone.

Castillo

@Summer at first I thought you were talking about pushing and pulling film but as I kept on reading I was reminded of this video. I do not have a higher end camera to test this out but I wonder if this applies to stills as well as video.

Summer

@Castillo I like the demonstration of ISO noise that you have posted here. Interesting. I'm still not sure if it applies to this "digital pull" thing on stills but I doubt it at this point. I'm not going to pursue the research into this question because my camera's settings do not have the necessary ISO stops that are required anyway. If I should ever come across more information about this in the future, I'll start another thread. Thanks.

dencal

Folks

YES! Noise applies equally to stills. If you examine the lab tests of cameras, one of the carefully examined attributes is the noise distortion at higher ISO levels. I becomes evident at the boundaries of say, a roof and a blue sky and shows edge breakup and color bleed, more insidiously it can introduce granularity in surfaces where there is none.

For our purposes though noise at high ISO is both easily avoided or ignored.
I could post some links but take my word for it, these lab tests are a good nights sleep on every page.

Denis

rgr

ISO is not a digital camera standard (yet). It's a body of standards from different places, and the film speed standard we generally refer to as ISO was actually an ASA (now ANSI) standard based on chemical tests done in the late 1930s which yielded a simple arithmetic formula for factor of 2 changes in light, which was the simplest to date (others generally used logarithms which are more complicated to reason about quickly).

There are efforts to standardize different aspects of photography across chemical and digital realms, including things like low light performance, but most of those efforts are still in the discussion phases. In the digital realm, what camera makers refer to as ISO is indeed an equation, not a standard.

jrbgolfs

Thought this was a cool quick reference guide on various aspects of the camera. @David_Quinn_Carder feel free to let me know if it has any value. Thanks,




Josh

Summer

@jrbgolfs Josh This is the best graphic I've seen about what I call the Big 3 (Exposure Triangle) in photography. Thanks. Summer

[Deleted User]

Video noise and noise in still images are a bit different, even though they're caused by the same thing. With video, if you have the processing power and enough time, you can remove a LOT of noise without noticeably affecting the rest of the image. This is because you can run an analysis across hundreds or thousands of frames, identifying which part of the image is noise and which part is "signal". I've done this before but for example, it's far, far too time-consuming to do on most DrawMixPaint videos that we're trying to post without an extra day of delay. Which is unfortunate because some of our shots (like our palette shots, typically) use a cropped-sensor mode since we don't have good zoom lenses, and anytime you are using a smaller sensor or smaller portion of the sensor, you're magnifying the noise.

With a still image you can't run an analysis like this, however noise is also less noticeable because it's one set of noise, not lots of sets changing every fraction of a second. And noise is easier to avoid, even in low light, with certain types of still shots (any situation where you can set your ISO low by setting shutter speed to be slow and/or the aperture to be wide). With video you're usually stuck with a certain shutter-speed/frame-rate combination, so you only have aperture to play with, so it's more likely you will have to shoot with the ISO up.

Anyway, don't overthink it unless you get a job as a video camera operator or something. Just do what I mention in the guide — take lots of shots, check the ISOs used, establish how much is too much for your purposes, and keep your ISO below that when you have a choice. When possible, keep the ISO as low as you can, but don't compromise shutter speed or aperture for it, ISO is the least important for the purposes of getting good source material to paint from unless it's truly excessive.

Summer

David_Quinn_Carder said:

any situation where you can set your ISO low by setting shutter speed to be slow and/or the aperture to be wide

This is the exact phrase I tell myself just before I take a photograph--only it's more like LOW-SLOW-WIDE (on a tripod and with a cabled shutter release). I'm glad to have it confirmed here by you. I'm afraid that you and everyone here have contributed so much to my question that my response is inadequate. You can be sure that I will save this thread and refer to it from time to time so your efforts are not wasted. There's a lot to take in and some of it is beyond my understanding at this time. I thank you all very much. Summer

Summer

@Kingston It's articles like these that seed my knowledge. Thanks.