So, when I took images with the Mamiya RZ67 together with the Zinstax (Instax film back), and used it indoors - the ISO 800 was fine - except that when doing so in warm light indoors, you get slightly underexposed images - because of the warm nature in the light, tend to do so. Also the motive contrast is usually lower, which means the image also turns out darker. I added almost 1 stop (ISO 400-500) in order to get lighter Instax images.

Now the outdoor images I took the other day, showed severe overexpose, when i had the light meter set to ISO 800. At least 2 stops, perhaps even 2.5 stops. What could be the reasons for such a deviation ?

Longer than normal central shutter speeds ?

Perhaps it was the lens' central shutter speeds are not really 1/400 sec, but longer. After all, these lenses are old from the 80s, and i kept the central shutter cooked. When you store Mamiya Sekor Z lenses for longer term storage, it was recommended to keep the shutter uncooked.

Now this is just theory, me thinking that the shortest shutter speeds in the lenses, perhaps ain't holding up - but maybe equal to longer speeds, more something like 1/125 sec. (+1.3 stops), or just 1/80 sec (2.5 stops).

I can't really judge that, unless perhaps i try out some iPhone app which aims at measuring the shutter speeds ? I could look for it. The Mamiya Sekor Z lenses, are electronically controlled. But they do have a mechanical shutter speed of 1/400 sec. Also when you go from the cooked state of the shutter, and uncook it - it will fire that mechanical speeds.

Perhaps I should try to measure it, and see - if there is something to the 1/400 sec speed - that it over time has gotten longer. That would explain why my daylight Instax photos, are so strongly overexposed.

Baby Shutter Tester

There are solutions on the internet. One is called "Baby Shutter Tester" (YouTube) - especially made for testing central shutters (in lenses) if i understood that correctly - albeit the video does show a camera with focal shutter in camera. Costs 75 € including shipping from France. That one marvels me, to be honest.

I also could test the Mamiya C330 Sekor lenses with it. Not just the Mamiya Sekor Z lenses for the RZ67.

I might give it a go.

Albeit i wonder how long the cable is between sensor and the device. Mamiya RZ67 + a long lens - means a lot of distance - and i doubt this testing device has a cable that long enough... !?

Maybe I should ask the guy before i buy.

No it isn't long enough... Damn !

I didn't find any acoustic measuring apps

any longer. You know, just to get a hunch of how the shutter speeds are on my Mamiya RZ67 lenses. I thought it would be good enough to get an indication. I remember that i once had such an acoustic measuring app a long time ago, but i doubt it is working on the newer Apple iOS.

PhotoPlug (Shutter Speed Tester)

Then there a provider from Germany for 40 € + shipping. The guy developed an optical sensor device you plug into a phone with a sound port (iPad 5 still has it) alt. with adapter for lightning or USB-C (Adapter cables need to be of “TRRS” type and need to have an internal DAC (digital to analog converter) present.

The lightning version that works together with the PhotoPlug Shutter Speed Tester, is Apple's own version. That brings the to 55 € + shipping.

So, with help of an iOS or Android app, you can measure camera or lens shutter speeds up to 1/500 (apparently things go critical at or above 1/1000 becoming garbled / imprecise).

I really wonder if my Mamiya Sekor Z lenses are still up to their task at their highest speed of !7400 sec. (I normally rarely used that speed, and was mainly using 1/60s, or 1/125s, occasionally even 1/250s in daylight. But the Instax film is ISO 800 - which in daylight makes you easily hit 1/400s while also having to stop down the lens' aperture s considerably.

One does assume that the highest speeds in a shutters are always a bit longer than they've been advertised to be. Over time, this gap tends to increase. Especially in mechanical (camera body) focal shutters.

Yeah, all those options.

And always money involved. (In one way understandable of course - yet also a bit annoying). I do marvel about the geniuses who create tools, though experiments leading to all kinds of devices (some good, some not so good).

It is kind of cool, though. With clearly creative spirits.

I admire that.

How to release the electronic shutter in the RZ67
without film / without film back ?

Since everything is electronically controlled in the Mamiya RZ67 with help of a 6v silveroxide battery - it might not be easy to know how you actually can test various speeds (in the lens) via the camera body - without film. Because the camera will refuse to trigger the shutter. You get a warning lamp illuminating in the Viewfinder. Or together with a red lamp.

Naturally, on the shutter button, suited in front of the camera, lower right side (from your own perspective as a photographer) - you should have it in the "white dot" position.

Now switch on the the right side of the camera, the lever to the "M" setting (multi exposure). Voilá - you can now trigger the shutter, without the film back attached - and see through the camera the various shutter speeds via the lens. The shutter speed you change at the wheel located on the left side of the camera (seen from the position, as if you are behind the camera).

Visual inspection

So, i checked the speeds of my Sekor Z 110/2.8 lens - and they seemed fine. Each shutter speed was shorter than the previous. OK. However - I did this on a different RZ67 camera - nor with the lenses i originally had used with Instax film. So, I have no clear indications yet of what is going on.

Additionally; I should clean the gold contacts in both lenses and cameras.

I made one test with Instax film, 110 mm lens and the older RZ67 - showing that the image was correctly exposed at ISO 800, at a speed of 1/250s with aperture ƒ11. However, the motive sucked: overexposed sky, and underexposed forest / trees.

The motive contrast was too large for the Instax film. Really finky film material I must say...

Not particularly colorful Instax

It also surprises me how dull the Instax colors often turn out, when using that film directly with a camera. Far less "pop", compared to when you print out images via an Instax printer.

What a difference !!

I am really not impressed at all.

Recalibration of my brain needed ?!

On the other hand - one can recalibrate my view and senses, as if i am using a contrasty, but strongly under-saturated film, with mediocre "blacks" (more dark gray than black). It reminds me as if using - almost - Black & White film. Then perhaps my focus should be more on shapes and patterns and faces, rather than colors. Here my brain needs adjustment when i use Instax film, but seem to misjudge the motive. They often turn out far duller and boring, than I see them with my naked eye. Especially the high contrast gives me headaches in judging the motive i see, turning out BLÄH.

Sensitive for color tint

Another thing I noticed is, that the film in daylight often turns quite blue. Especially if you get daylight indoors, while the sky is blue outside - everything shifts strongly to a cool color scale. For indoor photos, i will in the future use warm correction filters in order to get more neutral - or at least - less blue color cast in Instax images.

As i said, I find the Instax to be a rather funky film material... I am sure people are happy with it - given the tremendous popularity of Instax film - where Fujifilm really hit the jackpot year after years ! From a photographers perspective, i find the Instax film emulsion is leaving a lot to be desired.

Especially when used directly via a camera... Via a printer, things become more interesting colorwise. Albeit the overall contrast can at times be a bit weak with indoor images. (Kind of the opposite of what you get when using Instax directly with a camera)

Man, what have i gotten myself into ?!