Exposing Rollei IR 400

[dave_osborne]

Hi there,

I've just got some Rollei IR 400 35mm film to try out. I'm used to

Kodak HIE for which I compensate for a 090 light red filter by setting

the camera's ISO at 400 - where I believe HIE's actual ISO is 50 - so

that's 3 stops compensation for the filter with TTL metering.

So is it that case that because Rollei IR 400's ISO is 400 that with a

red filter and TTL metering I need to expose at 3200??! Doesn't seem

right to me!

Can anyone clear this up?

Cheers.

[neil_grant]

Your compensation for the filter sends you in the direction of less exposure - which can t be

right. Sounds like your camera/meter may not be working accurately. When I used HIE,

exposures were made through a 25A red filter, and under sunny conditions, correct exposure

was typically 1/60 @ f/11-f/16. By sunny 16 rule, suggests ASA of 32-64. Dev was ID 11

[Fotohuis RoVo]

The E.I. of the Rollei IR-400 with a RG695 or RG715 filter is around iso 25.

Much more is depending on the I.R. light availability.

 

The grain is very small for this iso 400 I.R. film.

An example of the Rollei IR film is in the attachment. Made last month Oktober here on the other side of our office.

 

Best regards,

 

Fotohuis RoVo

http://www.FotohuisRoVo.nl

 

Robert

[dave_osborne]

Not really less exposure for IR - it's just compensating for the fact the TTL metering can't pick up IR light. When you put on a red filter your camera TTL metering will expose 3 times longer (or 3 stops wider) because it's getting 3 times less visible light - but you don't want it to do that because the amount of IR light getting though is unchanged - hence bump up the iso to 400 from 50. On a non TTL metered camera you wouldn't have to do this.

I get very consistant results with HIE doing this - but I'm curious if the same recipe works for IR 400.

[dave_osborne]

Thanks Robert - low grain IR - that's the action I'm wanting in on!

 

So would the real ISO be similar with a 090 light red filter or higher than 25 do you think?

That makes more sense though - I'll be metering around 200/400 if that's the case which is much more sensible than 3200.

[Fotohuis RoVo]

It will be around iso 100 - iso 160 for this I.R. film which is sensible till 820 nm, in combination with a (light) red filter.

This example was with a Heliopan RG715 nm filter (M645 Pro-Sekor 2,8/55mm, 35mm testback). Development with RHS/AM74. Compared with HIE, this Rollei I.R.-400 film is very easy in handling.

 

You can load in very subdue light, but 100% dark is not necessary.

This film will be also available in 120 rolfilm and 4X5" format next month.

 

Best regards,

 

Robert