Correct ASA Setting for 160 ASA Film

[russelljtdyer]

Not long ago I purchased a Zeiss Ikon camera and a Zeiss 35mm f/2 lens. I'm thoroughly pleased with them. However, I have a set of questions about using the camera which might improve the exposure of my photographs.

I like to use Kodak Portra 160 VC & NC film. When I set the ASA setting on the camera for 160 ASA film, I'm not sure whether to set it to 100 or the notch between 100 and 200 ASA. So, to be safe, I've been shooting with the ASA set to 100. The results of setting the camera to 100 have been fine. However, I'm wondering if I could do better.

The manual that came with the camera cautions "to make sure to set film speed exactly at a notch position, not in between, otherwise proper shutter speeds will not be shown in the Viewfinder." Of course, I'm not sure if between 100 and 200 is not a notch position since there is a dot at that point and it does somewhat click there. Assuming it's not and playing with it, the shutter speed does show in the viewfinder and seems right when set it on that unnumbered notch. In the few tests that I've done in Aperture priority mode, the shutter speed calculated by the camera is the same for an ASA of 100 and '150'--assuming that is the speed in between 100 and 200. So, again, I've been setting it to 100 and it's been working fine.

Still, should I set it to the supposed value of 150? For that matter, is that notch in between actually a graduated ASA, or is it still just 100 with an extra notch to give space between the text for 200? If I'm to use 160 ASA film, would I do better to set the camera to 200--160 is numerically closer to 200 than 100--and adjust the exposure compensation, either up or down? If so, by how much for what general lighting conditions? What do y'all recommend?

 

[Rob-F]

Is this the Zeiss ZM for Leica lens mount? Seems odd that it would not have two settings between 100 and 200. Those two setting should be for 125 and 160. Yet it has only one? Presumably it would be 140, the geometric average of 100 and 200. But I can't remember there ever being an ASA 140 film (I'm old enough that I think I would know if there had been, but maybe not).

Well, I would be inclined to put it on the in-between dot/notch. That is so close to the film's box speed that it's got to be OK. Color print film generally performs quite well with mild overexposure. The fact that you are getting good results at 100 is consistent with that.

Funny there's only one in-between setting, though.

 

[keepright]

Each of those dots between the full-stop iso values does count as a 'notch position', so as Rob says, you'd be positioning the dial to the first dot below 200 for an iso setting of 160.

You can also do the same adjustment by dialling in exposure compensation, but I personally find that the less math I have to do, the more creative I can be.

 

[lic4]

I've always rated 160VC as 100 ASA film for good results. It's generally a bad idea to underexpose (rating at 200), and often people overexpose their negatives slightly to make the colors and saturation pop.

here is a helpful thread on rating 160VC:
http://www.flickr.com/groups/portra/discuss/72157600276730372/

**EDIT: I should mention that if you rate it at 200ASA, you might not notice any problems because of the latitude, but I don't think it would be as nice of an image as rating it at 100ASA.

 

[akremer]

160, 80, 40 - if you can't get it on 160 then put it as close as you can on the overexposure side eg 100.

 

[Juan Valdenebro]

160, 80 and 40 for me too... But metering in camera makes no sense if you're considering (and it's good!) that precision level... Your scene's reflectance will make your camera meter at different ISOs no matter the ISO you set... If you don't have intermediate ISO settings, and plan to meter with camera, set 100 and avoid light sources, and meter a part of the scene where there are both dark and light subjects, or a medium one...

Cheers,

Juan

 

[Mister E]

The Ikon has a setting for 125 and 160 between 100 and 200 on the ISO dial.

 

[jpberger]

That film has enough latitude that a stop one side or the other won't matter that much, especially if you lean towards over exposure. That said, the meters in most cameras is geared towards transparency film, which will mean you will tend to underexpose negative film if you rate at box speed. I.E with neg you want to expose for the shadows and with slides you want to expose for highlights, the exposure for an evenly lit scene will be the same for a slide and a negative of the same nominal speed, but with a high contrast scene the negative will be better with a stop more exposure than the negative. I set the autoexposure to 80-125 for 160 speed negative film. As far as the shutter speeds that show in the viewfinder, my understanding is that the resolution of the display is in full stops just like the voigtlander
"a" cameras, so anything less than a full stop change in film speed setting won't necessarily change what you see in the viewfinder. The electronic shutter is step less, however, so it does change the actual exposure.

 

[semilog]

If you were shooting a Leica M3-M6, the shutter would (at least at some speeds) in all likelihood be off by the <0.2 stop between ISO 140 and ISO 160. Don't worry about it and, as others have said, err on the side of overexposure.