Consistently 1 stop under exposed.. thoughts?

[PaulN]

Hi all,
I've been using my R-D1 since December 2004 without any problems. In the last few months, I've been noticing that all of my photos are consistently 1 stop under exposed. I have a Sekonic 608 that I use as a light meter with other cameras and have never had any issues with it.

Recently when doing some studio shots, I noticed that at 1/125, the flash sync speed, I was seeing bars on the shots. I dismssed them and unfortunately erased them. I shot the shoot at 1/60 and everything was fine. It is only now that I realize that this could have been an a sign on a larger problem.

My theory is that my shutter may be operating 1 stop faster than what is on the dial. 1/125 is really 1/250, etc. Has anyone seen anything like this? Is it even possible? I'm going to run some tests with other cameras side by side to verify..

 

[jlw]

I suppose it's possible, although I haven't seen it.

But if the shutter were simply traveling too fast (i.e. closing blind releasing too early) then you wouldn't see "bands" in flash shots -- you'd just see that the edge of the frame was unexposed. Banding suggests that the blinds are traveling at an uneven speed, which certainly could also cause underexposure effects.

How about shooting a lot of test shots at various shutter speeds of an evenly lit surface, and then check them with Photoshop for variations in density? That should give you a clue as to what is going on.

 

[mfunnell]

When you say that it is consistently underexposing by a stop, is that apparent in the histogram for the photos? Underexposure should result in a histogram gathered to the left (lots of dark values) with fewer values to the right (few light values) and often tapering off before reaching 255. If that's the case then it probably is underexposing. If the histogram looks OK but the meter disagrees with an external light meter then it may just be that the sensitivity of the sensor is greater than its nominal ISO value. (For example, ISO200 may really be ISO 320 or whatever.)

Just a suggestion - I'm not familiar with the sensor of the RD-1. Of course, that wouldn't account for flash sync problems but you're unclear on whether that's an on-going issue.

...Mike

 

[pfogle]

...My theory is that my shutter may be operating 1 stop faster than what is on the dial. 1/125 is really 1/250, etc. Has anyone seen anything like this? Is it even possible? I'm going to run some tests with other cameras side by side to verify..

One way to test your shutter speeds (it's a bit rough, but should do in this case) is, if you've got access to a record player, put a disc on with a white strip of paper at the highest speed on the turntable (78rpm is best, but not that common these days) and then measure the angle the strip has turned through during the exposure. At 78rpm, a 60th of a second should give an angle of approx 7.8 degrees, at 45rpm a 60th will give 4.5 degrees etc...

-ps I don't think this will work above 125th as the shutter will then be a slit rather than fully opening. Also, since it's a focal plane shutter, the image of the strip will probably be curved, so care needed to measure the angle!

Another thought is to check the shutter speeds in the exif data on your jpgs. If the shutter is firing at the next higher shutter speed, then 1/1000 and 1/2000 should give the same exposure, as that's the limit of what the shutter is designed to do mechanically, AFAIK.

Keep us posted!

 

[jrgoldman]

R-D1 underexposure

R-D1 underexposure

My R-D1 has always underexposed by one stop. I leave it permanently on +1 as the base setting and no problems.

I asked about this here last year and someone said it was not unusual.

 

[emraphoto]

i'm not sure about the flash sync issues but every review i have read states the rd-1 underexposes. there was a post here a few days back? comparing the rd-1 and m8 images... the sure fire way to identify the rd-1 image was that it was underexposed.

 

[iml]

My R-D1s routinely underexposes slightly too, presumably to prevent highlights blowing out. I shoot raw so I correct it in post processing.

Ian

 

[PaulN]

Sorry for the lack of updates; I haven't had an opportunity to setup a test environment.

When people state that the camera underexposes, are they referring to the meter or the sensor? In my situation, it is the sensor that is underexposing the image by 1 stop. In other words, if my Sekonic states 1/60 @ f2.8, I'll have to use 1/30 @ f2.8 (or alternately change the aperture if the DoF won't be an issue).

When I meter the scene with my old D60, and then shoot it on manual with the metered readings, the image is spot on. It is only with my R-D1 where I am continually increasing the final image's exposure by one stop in the post-processing.

 

[Benjamin Marks]

I also keep the exposure compensation for AE at 2/3 stops over. However, I find that when I use a handheld meter and set the exposure manually that everything is fine. I think it's an AE bias. And, well, that's what the compensation dials are there for.

Ben

 

[mwooten]

Paul,
Like Ben, I tend to leave my RD1s set on "AE" with it set a notch below +1 on the dial. If I'm using my 28mm Ultron, I'll set it on the +1 mark or a notch above.

I just took three shots with my camera with it set on manual. I used my Polaris meter set on incident to measure the light falling on the subject. The meter called for 1/60 @f4 -- I shot at that as well as 1/30 and 1/125. The camera did well when set to the indicated 1/30 @ f4, (but I did like the added range the -1 shot gave).

If I get a chance this week, I'll try a better test using both reflected and incident light from the handheld meter vs. the in camera meter.

Take care,
Michael