Sekonic target for quality control

[whojammyflip]

I thought I would share an idea, making quality control a bit easier. I just shot a negative of the Sekonic target, number JQ5797, at the metered off 18% recommended exposure settings, and processed according to the recommended processing for Rollei 100, in APH09 at 1:50 of 12 mins.

Using a Darkroom Automation meter, I can measure off the single frame the densities of the various patches which are factory calibrated. This means that I can know whether my processing and rated film speed are off (I think the film speed needs to be rated at 50 seeing this).

Additionally, I then printed at Ilford Grade 2 using a condensor enlarger, onto MG IV, for 10s, and generated a print, which can then be compared to a Kodak scale, to see where the densities end up. It looks to me surprisingly that the contrast is a touch on the high side, even though the difference in the negative between -2.33 and +2.33 EV was 2.5 stops (which means that the negative gamma is lower that the target of 0.6).

I'm trying to link to a photo I stuck on Flickr as Photrio was being stubborn and preventing me from uploading directly a shot of the final print.

https://flic.kr/p/2m9pJmS

 

[Bill Burk]

That target is a very useful design. I particularly like the 1/6 stop series of grays. You should have a lot of fun refining your understanding of film speed, exposure placement and tone reproduction.


Don’t conclude the speed is 50 for a 100 speed film though, as you may not have reached the ISO parameters. A single shot from that target won’t reveal that. Instead, evaluate it as if film is really what they say… 100 and see how your ideas fit.

 

[whojammyflip]

So, this is my thinking for the film speed: the transmission density of the -2.3 EV panel was 0.19 in log 10 units, relative to base + fog. This is close to the target density of 0.17 for Z1.5 as mentioned in the WBM book. So its not really Z 2.5, but Z 1.5.

 

[Lachlan Young]

printed at Ilford Grade 2 using a condensor enlarger, onto MG IV, for 10s,

It looks to me surprisingly that the contrast is a touch on the high side,

Ilford's baseline numbers for G-bar 0.62 should more or less put 7 stops on to G2 with a diffusion head (allowing for some flare). Depending on the condenser design you could need a neg that is a fair bit softer to land correctly on G2. What speed you prefer to set on your exposure meter is a reflection of your metering habits rather than the ISO test parameters used to determine ISO film speeds.

 

[Bill Burk]

So, this is my thinking for the film speed: the transmission density of the -2.3 EV panel was 0.19 in log 10 units, relative to base + fog. This is close to the target density of 0.17 for Z1.5 as mentioned in the WBM book. So its not really Z 2.5, but Z 1.5.

Mid tones aren’t good for speed testing because they vary widely.

What you might do is shoot the target so that it receives 3 1/3 stop less exposure than the gray card metering says. Then look at the 1/6 stop chips for the reading closest to 0.10 above base plus fog.

 

[john_s]

.......
What speed you prefer to set on your exposure meter is a reflection of your metering habits rather than the ISO test parameters used to determine ISO film speeds.

Absolutely agree.