Long Exposures on 120 film

[ansdkajnsdkjns]

A friend of mine and I were discussing long exposures on 120 film and he had

heard that metering with a digital camera (as I am doing currently, waiting

for my Sekonic to arrive from HK) or even metering more accurately with a

light meter on 120 film will underexpose your film. ie 120 films on a long

exposure require much larger shutter speeds than you would use for the

equivalent 35mm (what i dont understand if this is true is that 35mm film is

the exact same stuff as its roll equivalent?).

 

Unfortunately i havent shot a 35mm and 120 in the same light conditions with

the same type of film to compare, but i do have an example...

 

Shooting very low light (a factory lit up by car headlights from a nearby

bridge), f3.5 30 seconds on my canon 30D with ISO 100. i set my hasselblad on

f2.8 shooting astia 100F on exposures of 1, 2, and 3 minutes (by this time i

already noticed that if i exposed the same settings as my digital then the

shots would come out horribly underexposed). 2 minutes came out as the most

well balanced exposure, so...

 

f3.5 30" ISO 100

comes out the same as

f2.8 2 minutes ISO 100 on 120 film

 

i have also noticed the same on velvia 100F which is my film of choice. i have

only been shooting 120 for under a year so please feel free to drown me in

superior knowledge!

 

thanks, sacha<div></div>

[russ_britt3]

Because the film surface is larger it requires more light.......

 

 

 

 

No , just joking. Its the same exposure for the same asa as 35mm film. Some 120 films are slower, 35mm triX is 400, 120 triX is 320.

[justinblake]

One thing you will have to compensate for on long exposures is reciprocity failure (this applies to all film not just 120). The longer your film is exposed for the less sensitive it becomes so you will have to extend your exposure to compensate for this.

 

Most popular films have reciprocity charts floating around on the net that you can use to calculate how much correction is needed.

[justinblake]

As an example for Velvia 100F, exposures up to 1min require no correction, 2min correct by 1/3 of a stop, 4min correct by 1/2 a stop, 8min correct by 2/3 of a stop.

[SCL]

Since your exposure meters don't have a setting for camera type...there must be a message here. All joking aside, your friend is either misinformed or you misunderstood him.

[john_gleason1]

"35mm triX is 400, 120 triX is 320."

 

<p>

No, there are <i>two</i> versions of Tri-X in 120 size; one is ISO 320 and the other is ISO 400.

[ilkka]

One could draw the casual conclusion that large format film needs more light because the lenses are slower and often stopped down more, and medium format similarly is slower than small format. So one needs to use long shutter speeds more often and needs to compensate for the reciprocity failure more, and more often. But that is not due to the film.

[noah]

The difference may be between digital and film, not 35mm and 120. Digital doesn't suffer

from reciprocity failure, as mentioned above.

 

Have you had the same problem with short exposures? If not, you have your answer.

 

Also, digital may have more shadow detail than film, so you may in fact be underexposing

your digital photos slightly without really noticing it, but with chrome film it will be visible.

And on top of that, there's no absolute guarantee that iso 100 on your 30d matches iso

100 film. I've found that there is some variability in the iso sensitivity of digital cameras. I

have two identical bodies, and if I shoot the same scene with the same exposure and lens,

the files are not identical.

 

However, you could shoot the same scene on film with 35mm or MF or 8x10 and the

exposure would be the same, assuming no bellows factor or reciprocity failure.

[ken_schuster]

Sacha - Justin Blake is right, although not entirely technically correct... but it's fine to think of it that way.

 

Regarding large format film: View camera work often relies on small diameter apertures, such as f45 (usually along with tilting the lens and/or film planes), to achieve long depth of field or other effects. Additionally, view camera work often involves close-up photography. Usually, that means the "accordion" between the lens and film is extended longer than the focal length, resulting in "bellows extension factor" which must be calculated in addition to any reciprocity failure... and any filter factor.

 

By the way, the other side of long exposure compensation is short exposure compensation. Your light meter doesn't tell you that, either. Unfortunately, many photographers discover it after looking at film exposed with very short duration electronic flash, and being disappointed by severe underexposures. Some units flash at 1/20,000 of a second, or even shorter, when set on automatic and a light-color subject is close. For most film, that is way too short for anything more than a "ghost" image to develop, even though "according to the numbers," the flash exposure was correct. Many flash manufacturers publish their flash duration data.

[classcamera]

I shoot a many rolls of 120 at night, mostly Kodak Tri-X, and Verichrome Pan, however sometimes I shoot Efke R-100.

 

My take on metering is that you will have to decide what you really want, shadows or highlights, meter for either then expose appropriately. As for the Reciprocity failure--WHO CARES! This is only a technicality for most pictures as what it describes it the amount of silver on the film, doubling as the exposure doubles, once all the silver is exposed then it can no longer double, so the film is said to suffer reciprocity failure. This in a night shot will only effect the highlights and not the shadows. So it begs the question to ask, how dense do you want the highlights anyway? If you exposed for the shadows then they got there 4-8 stops extra anyway and you will need a healthy pull in some type of compensating developer just to (split contrast) print them.

 

If you are shooting at night forget reciprocity and just try to get a negative with low enough contrast you can easily print it.

[stwrtertbsratbs5]

Try Fuji Acros sometime. No reciprocity compensation is needed until the exposure exceeds 2 minutes, and then you only need 1/2 stop.

[frankz]

As evrybody has said, exposure is the same for a given speed film, regardless of size.

 

 

This reminded me of something I told my daughter as a joke when she was 4 or 5 years old. She asked why the black and white keys on my keyboard.

 

 

Oldest joke in the world - 'The white ones are for weddings and the black ones are for funerals'.

 

 

At a parent teacher meeting some time later, her music teacher asked me about where she got that - seems the teacher almost fell out of her chair laughing when my daughter recited what dad had said.