True ISO rating for Portra

Hello everybody. I wonder that is the ISO rating for Portra is true

rating for both ISO 400 and ISO 160. Or I have to set to ISO 200 or

320 when using Portra 400 and set to ISO 100 when using Portra 160 for

wedding and portrait.

I would appreciate any suggests and comments on this. Many thanks.

John:

I did a portrait sitting this weekend for an engaged couple and used Portra in a "work" setting for the first time. I used the 160 VC and rated it at 100 with good results. Regardless of what our friends at Kodak say about rating this film "right on" I would suggest treating it the same as you have with other films.

I have tested the Portra 400 thoroughly and it really should be rated at 400. It does have a very wide latitude for under/over exposure, but the best color reproduction (accuracy) was at ISO 400.

Well, I would not claim to be an expert here. I was in the local "pro" shop today (Glazers) though, and the clerk behind the counter was discussing Portra 160 with a customer and advising him to shoot it at 100. She said it really was more of a 100 film and negs would tend to come out a little on the 'thin' side if you notched it up to 160. She said she didn't know why they decided to call it a 160 film and even the local Kodak rep recommended shooting it at 100 ISO.

 

I had to concur, as I had just gotten my first roll of 120 format portra back from the printer, which I shot at 100 ISO, and it turned out very well. Definitely not overexposed. For what it's worth.

What I have heard meshes with what has been said above. My lab, (Prolab in Seattle) said that Portra 400 is true and should be rated at 400, but Portra 160 should actually be rated more around 125 to prevent underexposure.

 

-John

I have yet to use the new films but one of the UK pro photo magazines did a test both in the studio and outdoors of all 4 films in 120 format. They exposed all the films at correct, -2 stops and +2 stops.

 

Their conclusions:

In the studio there was no difference in grain structure on 8" prints. Also no blocking of highlights and increased shadow detail on the overexposed shots. On the underexposed shots the shadows did not block, highlight detail was enhanced and no degradation of color.

 

Outdoors underexposure was not tolerated well in the 400asa films (2 stops). 2 stops overexposure added greatly to the color saturation. They would rate the 400 films at 320 or 250.

 

The reviewer concluded the films could be used interchangeably with required DOF being the criteria used to select a film. They also felt that "vivid" versions gave colors with more depth.

 

Hope this helps.