ELi5: Under Expose And Over Develop

Messages
8,275
Name
Ian
Edit My Images
No
Please help... o_O

So, I (think that I) get that when you push film you intentionally under expose it and over develop. I understand the concept. I also understand how this affects contrast in the overall image. Similarly, I (think that I) understand the concept of Over Expose and Under Develop where you "pull" the film to try and retain dynamic range or reduce contrast. Historically, I've always pushed film to make it work in lower light and that's been about the extent of it.

What's been keeping me awake at night is that [in my head] increasing your ISO from 400 to 800 is actually over exposing the film, whilst the internet reckons it's the other way around. In my (digital) head - if I take a correctly exposed image at 400, then I up my ISO to 800, I will get an over exposed image (because I've given the sensor too much light). In short - I cannot understand how increasing the ISO under exposes....

I'm missing something fundamental in the language here but I can't see it and have not found an internet explanation that makes any sense. I think the wire in my brain is just missing, so an ELI5 would be very much appreciated.
 
Last edited:
increasing your ISO from 400 to 800 is actually over exposing the film, whilst the internet reckons it's the other way around.

It is underexposing though, if you put 400 speed film in your camera and set the ISO dial to 800, the camera will think it's 800 speed film which is twice as sensitive as 400, and will expose the film half as much.

edit to add- With a digital camera if you change the ISO from 400 to 800, you are actually changing the ISO, so overexposing it. With film, if you change the ISO dial from 400 to 800, it's still a 400 speed film. The camera just thinks it's 800, so will change the shutter speed (or aperture) to suit an 800 speed film. This will underexpose by a stop.
 
Last edited:
Thanks Carl :)
 
Yes, exactly as Carl said. The way to think about it is that changing ISO in a digital camera is equivalent to physically changing film. Whereas all you're doing when you change ISO on a film camera is altering the meter's calibration so it under or over exposes.
 
Also I must be getting old as I had to Google what the heck "EL15" meant.

Wikipedia tells me it's a class of electronic locomotive used in Sweden.

Thankfully the Urban Dictionary had a more sensible answer, so now I know!
 
Also I must be getting old as I had to Google what the heck "EL15" meant.

Wikipedia tells me it's a class of electronic locomotive used in Sweden.

Thankfully the Urban Dictionary had a more sensible answer, so now I know!

Yep - also had to look it up.

But have to say, I do like the concept...especially as you can reply with, "ELI4", if you still don't understand!
 
EL15? so far from google got to:- "Nikon is offering to replace old under performing Nikon EN-EL15 batteries for free" :D
EL15 must be the wierdest slang ever, why EL and why 15 any young-ens can explain :rolleyes:
 
I think it's my reddit time. I found the "Explain it like I'm 5" subreddit and spent ages on there learning stuff I never knew I needed to know. (It's eli5 not 15)

https://www.reddit.com/r/explainlikeimfive/

Also, in answer to the OP, my film cameras are not automatic, so I'm not sure if that has made things worse.

(OP = original post...) :exit:
 
Last edited:
I think it's my reddit time. I found the "Explain it like I'm 5" subreddit and spent ages on there learning stuff I never knew I needed to know. (It's eli5 not 15)

https://www.reddit.com/r/explainlikeimfive/

Also, in answer to the OP, my film cameras are not automatic, so I'm not sure if that has made things worse.

(OP = original post...) :exit:

I've just spent five minutes reading that page and so far I've learned about seven things I didn't even know I didn't know. Going to spend all day dropping these new found facts into conversations at work to sound like I'm intelligent :LOL:
 
What's been keeping me awake at night is that [in my head] increasing your ISO from 400 to 800 is actually over exposing the film, whilst the internet reckons it's the other way around. In my (digital) head - if I take a correctly exposed image at 400, then I up my ISO to 800, I will get an over exposed image (because I've given the sensor too much light). In short - I cannot understand how increasing the ISO under exposes....

I'm missing something fundamental in the language here but I can't see it and have not found an internet explanation that makes any sense. I think the wire in my brain is just missing, so an ELI5 would be very much appreciated.

When you change the ISO in post, you're doing so after the image has been metered and exposed for 400. That's like setting 800 in the camera and then over-exposing by one stop. If you had set to 800 and exposed correctly, it would be fine. With film, you set the ISO in-camera (or on a separate meter), then meter and expose. If you had set to 400 and then over-developed the film as if to push it one stop, the neg would look like it was over-exposed as well. (It likely wouldn't be classed as an ISO change, however, due to the effects of the chemical process not satisfying the criteria for an ISO rating with film.)
 
Last edited:
So, I (think that I) get that when you push film you intentionally under expose it and over develop. I understand the concept.

Pushing refers strictly to overdevelopment; your exposure (i.e., under exposure, over exposure, or "correct" exposure) does not technically impact your (in)capability to push in any way.

For instance, I can overexpose all of my exposures and still push the film. That said, the practice of pushing is often paired with under exposure.
 
Last edited:
Back
Top