aporodagon
3-Feb-2009, 00:29
Trying to come to terms with regard to what exposure to use when using filters, I assembled 4 meters, some filters and several film types. Each of these represents a variable to be tested.
This test was run with 120 film because the electronically controlled shutter on a
Rollei 6008AF would be more accurate and precise than any LF mechanical shutter.
The meters tested were a Sekonic 778 spot meter, a Sekonic 608 multifunction meter, a Pocket Spot meter and the meter housed by a Rollei 6008AF.
Films were 120 format 320 Tri X, HP5+ and 100TMX (the films I use the most).
Filters were my most commonly used Heliopans, a Wratten 8 medium yellow (ff 3.0X), a Wratten 13 green (ff 3.0X), a Wratten 22 orange (ff 4.0X), and A Wratten 25 red (ff 8.0X).
Target was an 18% grey card. Film was developed N (to 0.75 DU for Zone V) and read on a densitometer. The meters were secured to a tripod immediately beside the camera such that the reading angle was fixed. Meter readings were were transferred to the Rollei which has manual selection of shutter speeds to 1/3 step. For meters with 1/10 stop display, the closest approximation in thirds of a step were made.
After a reading though a filter was transferred to the camera and an exposure made, a reading without a filter was exposed on the next frame. Therefore, the difference in an exposure through a filter and without a filter should show the amount of correction that would have to be applied if one metered through a filter.
Differences of 1/3 of a stop are probably insignificant (e.g. the Pocket Spot only reads in 1/3 steps - a reading of , for example EV 13 * * could be between 13 * and 14 EV).
The results (see thumbnails) suggest that a meter may be keyed to a particular film (e.g. the Sekonic 608 to 320TRX, and the Sekonic 778 and Rollei to HP5+). The Pocket Spot seems to cover both these films equally well. 100TMX , on the other hand would require a correction factor to be used, regardless of which of these 4 meters was used.
This may be justification for having more than one meter if more than one film type is used. This doesn't represent a real world situation unless you specialize in photographing grey cards but hopefully, this will give some insight and a starting point to metering through filters. As in most things, YMMV. Proceed with caution and do some testing with your own combinations, especially with coloured objects in addition to neutral targets.
John
This test was run with 120 film because the electronically controlled shutter on a
Rollei 6008AF would be more accurate and precise than any LF mechanical shutter.
The meters tested were a Sekonic 778 spot meter, a Sekonic 608 multifunction meter, a Pocket Spot meter and the meter housed by a Rollei 6008AF.
Films were 120 format 320 Tri X, HP5+ and 100TMX (the films I use the most).
Filters were my most commonly used Heliopans, a Wratten 8 medium yellow (ff 3.0X), a Wratten 13 green (ff 3.0X), a Wratten 22 orange (ff 4.0X), and A Wratten 25 red (ff 8.0X).
Target was an 18% grey card. Film was developed N (to 0.75 DU for Zone V) and read on a densitometer. The meters were secured to a tripod immediately beside the camera such that the reading angle was fixed. Meter readings were were transferred to the Rollei which has manual selection of shutter speeds to 1/3 step. For meters with 1/10 stop display, the closest approximation in thirds of a step were made.
After a reading though a filter was transferred to the camera and an exposure made, a reading without a filter was exposed on the next frame. Therefore, the difference in an exposure through a filter and without a filter should show the amount of correction that would have to be applied if one metered through a filter.
Differences of 1/3 of a stop are probably insignificant (e.g. the Pocket Spot only reads in 1/3 steps - a reading of , for example EV 13 * * could be between 13 * and 14 EV).
The results (see thumbnails) suggest that a meter may be keyed to a particular film (e.g. the Sekonic 608 to 320TRX, and the Sekonic 778 and Rollei to HP5+). The Pocket Spot seems to cover both these films equally well. 100TMX , on the other hand would require a correction factor to be used, regardless of which of these 4 meters was used.
This may be justification for having more than one meter if more than one film type is used. This doesn't represent a real world situation unless you specialize in photographing grey cards but hopefully, this will give some insight and a starting point to metering through filters. As in most things, YMMV. Proceed with caution and do some testing with your own combinations, especially with coloured objects in addition to neutral targets.
John