Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Notices

Go Back   Film and Darkroom User > General discussions > Photography in general

  ***   Click here for the FADU 2015/2014 Yearbooks   ***

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 25th March 2014, 10:15 PM
gsingh gsingh is offline
Friend
 
Join Date: Jan 2014
Posts: 88
Default ISO limitations for film cameras

When looking at a lot of tutorials they often talk about opting for a higher ISO film when light is scarce. As far as I understand the higher the ISO the more sensitive the film is to light.

That is all great with a digital SLR when you can switch the ISO however on film you can't do the switch that easily. So my question is rather than selecting a higher ISO in darker scenes would changing the aperture/shutter speed have the same effect to selecting film of a higher ISO?

If so what would be the need in opting for a higher ISO film in the first place? Would it not just be easier to select a ISO film of say 100 and then as you move into darker settings just change the aperture/shutter speed instead of having multiple films of different ISO's?
Reply With Quote
  #2  
Old 25th March 2014, 10:44 PM
hastingsb hastingsb is offline
Friend
 
Join Date: Nov 2013
Location: Chester
Posts: 37
Default

Yes that's right, however under some low light situations your lens may not have large enough apertures (low f stop number) or you want to use a relatively fast shutter speed to avoid blur if handholding the camera or "freezing" movement within the frame.

Ben
Reply With Quote
  #3  
Old 25th March 2014, 11:05 PM
Mike O'Pray Mike O'Pray is offline
Friend
 
Join Date: Oct 2008
Location: Daventry, Northants
Posts: 8,968
Default

In a sense we're almost back to the manual metering mode. The camera's meter takes readings which depend on the film's ISO. It does this because it assumes that whatever you have set the film ISO at is the genuine film speed. So if you have a ISO 400 in the camera then the meter assumes, rightly in most cases, that the film is capable of taking good pictures at that speed.

You can of course re-set the ISO speed on the camera from the speed of the film so if the shutter speed of the camera with a 400 film isn't fast enough for the nature of the photo then 800 or 1600 might resolve that problem. However as I think you have inferred from your readings this doesn't really change the true speed of the film. It is still a 400 film and even with push processing you will lose some shadow detail at a higher speed. This may or may not matter greatly if the shot is a night shot where shadows tend to disappear anyway.

The only real way to get a higher ISO speed is to remove the 400 film and replace with say a 3200 film. The latter will give you a higher genuine speed but not the full 3200.

It is generally thought that the Ilford D3200 may have a maximum true speed of 1250.

On a brighter note there are many users who believe that the likes of HP5+ can be uprated to 1600 or even 3200 when required for night shots. However you need to be aware that 1600 and 3200 requires push processing and if you have 400, 1600 and 3200 shots all on the same film then the required push processing for the 1600 and 3200 shots will over-develop the 400 shots so acceptance of some compromise in the negs is required.

I hope this makes sense to you

Mike
Reply With Quote
  #4  
Old 25th March 2014, 11:06 PM
alexmuir alexmuir is offline
Friend
 
Join Date: Jan 2010
Location: Glasgow, Scotland.
Posts: 2,668
Default

You can see how this works by trying different film speed settings on your camera, without loading film. Indoors at night should give typical low light readings. An ISO of 1600, for example, will give you better shutter speeds for hand-holding than one of 100. If using a tripod, on the other hand, the shutter speed can be much slower, and a lower film speed would be ok. The slower film should give better quality negatives, but its not always practical to use a tripod. Recently I have been using B&W film rated at 1600 or 3200 ISO to avoid the need for a tripod. I have found short rolls of 24 exposures useful to avoid being stuck with a high speed film in the camera when subject matter changes and a lower speed would be preferable.
Alex.
Reply With Quote
  #5  
Old 25th March 2014, 11:29 PM
Maris's Avatar
Maris Maris is offline
Friend
 
Join Date: Jul 2009
Location: Noosa, Australia
Posts: 183
Default

In engineering terms a film with an ISO speed of 100 requires about 0.1 Lux.seconds of light to hit the film in order to deliver a well exposed picture. And this remains true no matter how bright or dim the subject matter external to the camera is. It doesn't matter how you get your 0.1 Lux.seconds. Lots of Lux and few seconds or few Lux and many seconds gets you the same exposure as long as the Lux multiplied by seconds product is the same.

The equation looks like this:
E = I x T

where E is exposure (Lux.seconds),
I is intensity (Lux),
T is time (seconds).

The usual challenge posed by dimly lit subject matter is that the maximum aperture of the lens sometimes delivers so little intensity (Lux) to the film that the exposure needs to be made up by increasing the exposure time (seconds). Long exposures can lead to blurring of moving subject matter or blurring of the entire picture if the camera is held in an unsteady hand.

The only way around this problem is to use a more sensitive film (higher ISO speed) that requires a lesser quantity of light for a satisfactory exposure.

Higher sensitivity films tend to deliver pictures with lower image quality due to increased graininess and reduced sharpness.

The digital world offers variable ISO values that vaguely mimic what different film ISOs do. Going for a high digital ISO value generates pictures with nasty speckles of electronic "noise". It may be a matter of opinion but I think the grain pattern of high ISO film has a beauty that the speckles of digital electronic noise don't match.
__________________
The word Photography first uttered and defined by its author Sir John Herschel at Somerset House, London on the evening of March 14, 1839: quote "Photography or the application of the Chemical rays of light to the purpose of pictorial representation" unquote.
Reply With Quote
  #6  
Old 26th March 2014, 12:36 AM
gsingh gsingh is offline
Friend
 
Join Date: Jan 2014
Posts: 88
Default

My theory was that you could stick with a particular ISO film such as 100 and be able to manipulate the shutter and aperture to get the right level of exposure in any giving setting. However, I think the problem with this is the shutter speed. If I wanted to take shots in darker scenes I could lower the shutter speed however lower shutter speeds means more potential for motion blur. The only way therefore to prevent motion blur AND get the right exposure level in darker settings would be to switch to a higher ISO film.
Reply With Quote
  #7  
Old 26th March 2014, 07:12 AM
EdBray EdBray is offline
Friend
 
Join Date: Oct 2011
Location: Plymouth, UK.
Posts: 350
Default

The other problem you run into at long shutter speeds (typically shorter than 1/2 sec) is the issue of reciprocity failure. This can be quite significant with some films (Ilford, Foma,) and insignificant with others (Fuji Acros).

The downside of reciprocity failure is that for longer exposures you need to add additional exposure to get the same result from the film. For FP4+ for example you have the following:

0.5 - 1 sec 1.5x
1 - 2.5 secs 2x
3 - 6 secs 2.5x
7 - 12 secs 3x
13 - 18 secs 3.5x
20 - 22 secs 4x
24 -26 secs 4.5x
28 -32 secs 5x

So if you take a low light reading that suggests a 30 second exposure you actually have to give an exposure of circa 2.5 minutes.

In my opinion there are only two benefits where using a higher end Digital Camera over a similarly specified Film Camera these are for high ISO work and teaching (due to the instant feedback available).

With sheet film each sheet can be developed individually so there is no issue with having to use a specific ISO for every image so the fact that you can do this with digital is slightly negated when using sheet film.
Reply With Quote
  #8  
Old 26th March 2014, 07:46 AM
Steve Smith's Avatar
Steve Smith Steve Smith is offline
Friend
 
Join Date: Dec 2008
Location: Ryde, Isle of Wight.
Posts: 1,102
Default

Quote:
Originally Posted by gsingh View Post
The only way therefore to prevent motion blur AND get the right exposure level in darker settings would be to switch to a higher ISO film.
Or a tripod if your subject is staionary.


Steve.
Reply With Quote
  #9  
Old 26th March 2014, 09:18 PM
JohnX JohnX is offline
Friend
 
Join Date: Jan 2014
Location: West Yorkshire
Posts: 134
Default

Quote:
Originally Posted by gsingh View Post
.....However, I think the problem with this is the shutter speed....
It is also aperture, larger apertures give a shallower depth of focus which can be problematic depending on the focal length, the distance from your subject and the depth of focus you require.
You're definitely getting it gsingh , you can manipulate settings and film but there are limits, you can't just dial in iso 128000 like you would with a digital camera, film just doesn't stretch that far easily.
Reply With Quote
  #10  
Old 27th March 2014, 07:04 AM
EdBray EdBray is offline
Friend
 
Join Date: Oct 2011
Location: Plymouth, UK.
Posts: 350
Default

Quote:
Originally Posted by JohnX View Post
It is also aperture, larger apertures give a shallower depth of focus which can be problematic depending on the focal length, the distance from your subject and the depth of focus you require.
You're definitely getting it gsingh , you can manipulate settings and film but there are limits, you can't just dial in iso 128000 like you would with a digital camera, film just doesn't stretch that far easily.
Not to want to be pedantic, but Depth of Focus refers to the amount of focus at the film/sensor plane, Depth of Field is the perceived amount of sharpness either side of the 'plane of focus'.
Reply With Quote
Reply
Support our Sponsors, they keep FADU free:   AG Photographic   The Imaging Warehouse   Process Supplies   RH Designs   Second-hand Darkroom Supplies  

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
APS cameras/film CornishChris Cameras - small format 12 13th March 2018 07:57 PM
Leica still makes film cameras Miha Cameras - small format 9 24th April 2014 02:58 PM
For Sale: 3 different 6x9 Roll Film Adapters for 4x5 Cameras EdBray Sale or Wanted 4 8th September 2013 09:39 PM
3D / Stereo Cameras and 127 Film CambsIan Photography in general 7 23rd December 2012 05:47 AM
New (old) Cameras Dave miller Cameras - Large Format 4 8th March 2012 04:37 PM


All times are GMT. The time now is 09:29 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.