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Thread: "True" ISO ratings of films

  1. #1

    Default "True" ISO ratings of films

    I have read that the film normally requires over exopsure by aboubt 1/2 or 1 stop. Cos the manufacturer also up their ratings. Was wondering where can i get "true" ISO ratings of films.
    I have heard that Press 800 must be exposed at ISO 640 to get good results? And NPH 400 exposed at ISO 320. What about other films? By overexposing films, will i encouter problems in scanning the negatives, as it will be too dark?

    Also another question, what are the difference between Press 800 and the normal Xtra800. Is it grain size? I have read the film characteristics, they are the same. Was wondering whether they renamed the film and sell it at a higher price.

  2. #2

    Default Re: "True" ISO ratings of films

    press800 is the pro version of xtra800

    practically no differences

    expose the film at their rated ISO will be fine

    those exposing at other ISO's are just somebody else's personal preference. to follow and try it otu or not is up 2u

  3. #3

    Default Re: "True" ISO ratings of films

    Quote Originally Posted by user111
    press800 is the pro version of xtra800

    practically no differences

    expose the film at their rated ISO will be fine

    those exposing at other ISO's are just somebody else's personal preference. to follow and try it otu or not is up 2u
    Any idea what so pro with the pro version? If not, i jus save my bucks for a cup of coffee.

    user111, have you tried overexposing the film? What are the results you achieved. Better image quality?

  4. #4
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    Default Re: "True" ISO ratings of films

    Usually the colours are "denser" when you overexpose films by abt 1 stop. Anyway, as a precaution, its always better to over than under when using film, so usually I tend to shoot 1 stop over for negatives. Not for the case of slides though, unless its supposedly rated at lower iso.
    If you understand my works, it's photography. If you don't, it's art.
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  5. #5
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    Default Re: "True" ISO ratings of films

    Quote Originally Posted by Splutter
    Anyway, as a precaution, its always better to over than under when using film,
    Colour negative film, that is. With slides, it's the other way round.

  6. #6
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    Default Re: "True" ISO ratings of films

    Quote Originally Posted by sweat100
    I have read that the film normally requires over exopsure by aboubt 1/2 or 1 stop. Cos the manufacturer also up their ratings. Was wondering where can i get "true" ISO ratings of films.
    The ISO documents cost $$$, so I can only offer some second hand information. The ISO sensitivity rating is based on the _minimum_ exposure to achieve a certain (small) reaction of the film. It doesn't say anything about the latitude of the film - and as long as the image contrast range falls within the latitude range, exposure variances do not matter much. Typically there are considerable reserves on the overexposure side.

    To make things more confusing, some manufacturers (e.g. Ilford) do not give ISO sensitivities, but "practical" sensitivities, whatever that may mean.

  7. #7

    Default Re: "True" ISO ratings of films

    Apparently several labs that i've asked have ceased to do push and pull processing for print film, so don't rate print film with the intention to push/pull, labs don't do it anymore.

    Slides/BnW are still ok.
    My Personal Folio (of random events and things)

  8. #8

    Default Re: "True" ISO ratings of films

    What speed you rate film is highly subjective and up to you. I used to rate the old NPH at 250 and the new NPH at 320. Fuji's superia does well at the printed speed, no need to overexpose, it's an awesome and cheap film. Also need to consider the scanner used if you are scanning.

  9. #9

    Default Re: "True" ISO ratings of films

    Quote Originally Posted by sriram
    What speed you rate film is highly subjective and up to you. I used to rate the old NPH at 250 and the new NPH at 320. Fuji's superia does well at the printed speed, no need to overexpose, it's an awesome and cheap film. Also need to consider the scanner used if you are scanning.
    I will be sending it outside to scan or scan using my coolscan III. Can film scanners take over exposed negatives like 1 stop? I will be using Press 800, NPC 160, potra 160VC and 400VC for a wedding this weekend. Any "recomeended" ISO setting on these films?

    Btw, if lets say I expose 400VC at iso 320. And I will be using it with flash, will the flash go and think that it is a ISO320 film and overexpose the film with a lot of light? Show i do flash compensation? Using a canon 580EX flash here.

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