Mjerenje brzine zatvarača na DSLR kamerama

Nakon Matjaževog članka o posjeti Nikonovoj tvornici i tvrdnje da brzina zatvarača i nije ono što se uvijek pokazuje, odlučio sam to i provjeriti na mojoj KonicaMinolta Dynax 5D.

Kod analognih kamera to je bilo jednostavno. Izvor svjetlosti na svjetlosni otvor ili na objektiv, i fototranzistor umjesto filma. Kod digitalnih kamera to nije moguće. Va�'enje senzora ne dolazi u obzir. Zato je ovdje primjenjiva jedino metoda odboja svjetlosti. Za to je bilo potrebno staviti M42 adapter i napraviti držač za žaruljicu i fototranzistor.

Prvo sam izmjerio vrijeme zadrške, tj. kašnjenja od pritiska na okidač (u ovom slučaju dizanje ogledala) pa do otvaranja zatvarača. Mjerio sam standardna vremena, počevši od 1/60s pa do 1/4000s i na kraju 0.5 i 1 sekundu. Rezultati su slijedeći:

Vrijeme od dizanja ogledala do otvaranja zatvarača je 50.6ms

1/60s=16.667ms, izmjereno je 16.7ms, iznena�'ujuće točno

1/125s, 8ms. izmjereno je 7,96ms

1/250s=4ms, izmjereno je 4.16ms

1/500s=2ms, izmjereno je 2.13ms

1/1000s=1ms, izmjereno je 1.105ms

1/2000s=0.5ms, izmjereno je 0.508ms

1/4000s=0.25ms, izmjereno je 0.254ms

0.5s, izmjereno je 0.509s

1s, izmjereno je 1.01s

Rezultati su zapravo za moj pojam vrlo dobri. Sve je oko 10% greške, što za mehaniku i kameru ulaznog razreda zadovoljava.

Test je napravljen kod sobne temperature, a tu su obično odstupanja najmanja. Prvom prilikom ću ponoviti test kod drugih temperatura i naravno, s nekim drugim kamerama.

Shutter speed accuracy in DSLR cameras

In the Nikon factory tour article, Matjaž pointed out that not all shutters are made equal – some are more precise than others. So, I decided to test my Konica Minolta 5D.

It did pose a bit of a challenge, though – with film cameras, all you had to do was replace the film with a light sensitive device. I decided I'd much rather not take the sensor out of my camera, so I had to measure the reflection off the sensor. It was relatively simple - I got a M42 screw mount to Minolta mount adapter, fitted it with a phototransistor and a light.

First of all, I measured shutter lag, i.e. the time between pressing the shutter release and shutter activation.

It takes 50.6 ms from the moment the mirror is raised to the moment the shutter opens.

And now, for shutter time accuracy:

1/60 s=16.667 ms. The measured value is, with the measured value of 16.7 seconds. This is surprisingly accurate.

1/125 s, 8 ms. The actual time is 7.96 ms.

1/250 s=4 ms. The actual time is 4.16 ms.

1/500 s=2 ms. The actual time is 2.13 ms.

1/1000 s=1 ms. The actual time is 1.105 ms.

1/2000 s=0.5 ms. The actual time is 0.508 ms.

1/4000 s=0.25 ms. The actual time is 0.254 ms.

0.5 s. The actual time is 0.509 s.

1 s. The actual time is 1.01 s

I consider these results to be very good, with a maximum error of about 10%, which is acceptable considering that this is an entry level camera.

The test was performed at room temperature. Note that these are the optimal conditions, with the smallest possible errors. As soon as possible, I'll repeat the test at other temperatures and with other cameras, so stay tuned.