iso 200 is not iso 200 with Sony

[denisbergeron]

I have a three months old Sony DSC-V1 (5MP f2.8 4x zomm and iso 100 to

800)<br>

I always find that the speed was always to slow.<br> Today I made a

test with my Canon Elan IIe and the Sony V1.<br> I set my Sony V1 to

f2.8 ISO-200 and with the ligth entering from the window, I got 1/13s

exposure, with the same setting on my Elan IIe 1/30s (the lens was

50mm 1.8 set to 2.8) ! <br>

I made an other test tonight, I take, my Elan IIe (with 50mm 1.8 set

to 2.8) my Minolta X-700 (with 50mm with 50mm 1,4 set to 2.8 and 28mm

2.0 set to 2.8) and of course my Sony V1. All of them mesuring the

light from a white wall lit by an halogen lamp with an iso-200 and

af2.8 setting !<br><p>

 

Here the result :<br>

Elan IIe 50mm f1.8 at f2.8 : 1/125s<br>

X-700 50mm f1.4 at f2.8 : 1/125s<br>

X-700 28mm f2.0 at f2.8 : 1/125s<br>

Sony V1 (wide open equiv 38mm at f2.8) : 1/50s<br><p>

Someone know why ?<br>

[bobatkins]

Presumably the ISO rating on the Sony is wrong.

 

This isn't unknown in the world of digital cameras. I think some of the Canon P&S Powershot consumer digicams tend to be a bit pessimistic about ISO to the extent of about 1 stop. So ISO 50 on them gives the same shutter speed/aperture combination as ISO 100 on many other cameras.

[gsbhasin]

Agree with Bob on the Canon G2 at least. Its ISO 50 is in reality ISO 100.

[Jochen_S]

I had some damned wrong exposure on slide film, when I used a Powershot 70 as a flashmeter. And I always wondered why my meter readings were totally unusable with the Canon...

A technical excuse for your reading should be that zooms eat light by having more elements than primes. But according to modern coating successes this can justify maybe 10% of the whole missing f-stop. I'm no consumer protection law expert, so Ican't tell you if you 'll have any chances if you take Sony to court. I suppose the whole stuff goes like this: A common p&s user has learned more than ISO 25 is good, so he likes to buy quite fast cameras. He has neither a handheld meter nor any other reason to check the camera setting. There is no technical reason to give right ISO ratings because there is nothing to combine (like camera & film) and maybe the industry also claims to give the ISO ratings somehow 35mm equivalent like focal lengths and by this way they can compare a wide open digital with a stoped down 35mm. Next thing is: Can you imagine how hard it is to explain to every usual 200 Film buyer that ISO 50 on a digital is quite the same?

[beerbrain_ronny_perry]

What if the Sony was the correct exposure, when I meter for film off something white I open up one stop cause I know that the white wall is faking out the meter, that would put me at 1/60th at 2.8,,instead of 125th at 2.8. When you go from ISO 100 to 200 on a digital camera, you are amplifying the signal, .In the video world we call it adjusting the gain.. going from 0db to 9db, that is one stop of light , the image sensor isnt getting anymore sensitive with the change of ISO/db..it is just amplifiying the signal .............along with the noise.

[denisbergeron]

I made other test today, on a not so sunny day, I get 1/125s with both my Canon ElanIIe and my Minolta X700 at iso 200 f4.5, with my Sony V1 I have to be at ISO-800 to have the same speed at f4.5 ! My Canon ElanIIe was on Center-weighted average metering, and the same thing with my V1, I don't remember how the X700 work,but anyway I don't have choice of metering. I also try other metering with the same result !

[craig_gillette]

So how do the pictures turn out? Anything appear to come out grossly incorrectly exposed?

[denisbergeron]

Everything are correctly exposed, but with 2 stop slower that it's supposed !

[kw_smith]

FWIW, my Canon G3 almost always over-exposes, even with a mostly white subject! Not judging by shutter speed, just the results. Using a -2/3 compensation keeps it to a minimum but I've had to dial in as much as 2 full stops. I have to pull the flash down some, too.