D800 ISO Moon Study

Okay, I was able to run an ISO study on the crescent moon of Sept 20, 2012. The images are straight out of the camera and the only adjustment made was the crop.

D800; 70-300mm; f-6.7, EV = -2.0. Each photo was shot in M and spot metered and shutter speed was set at point 0 on light meter.

ISO-100; 1/45 sec

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ISO-200; 1/45 sec

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ISO-400 1/125 sec

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ISO-800; 1/250 sec

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For whatever reason the ISO-200 seems a little brighter than the others and perhaps less of the moon was within the focus point, giving me a slightly lower reading on the light meter and hence, causing me to slightly over expose.... not sure.

I'm not sure what to conclude. With the exception of the overexposure at ISO-200, there doesn't seem to be much difference between them all.

And then I played around with the EV again. Despite reading up on it, I'm still not wrapping my head around the difference between lower the EV or speeding up the shutter speed but there is a clear difference. The closest thing I can come up with is that the EV attenuates the post sensor signal, much like a volume fine-tuning on a high end stereo. But despite not fully understanding it, it does produce some excellent results.

This photo was taken at ISO-100 with the EV= -5 and shutter speed at 1/250. The color is directly from the camera, I did not adjust the temp. I did bump the highlights up in LR as well as a little sharpening (typical PP) but I must say I really like the differences lowering the EV can deliver over shutter speed changes

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I think it gets better as the ISO goes higher to be honest with you. That is strange wouldn't you say?

The EV shot seems to have a lot more detail in it upon casual inspection.

Interesting deal MD.

I like the ISO 200 one myself. Looks really sharp. Nice shots, Dave.

Great photos mate, I am going to have to see how my 80-400mm VR handles handheld moon shots with the D800, the D80 did a good job last time I tried.

When I shoot good film like Fuji 160 Pro S or C I always rate it at 125. Problem is I don't have a meter on my F2 it is an Eye-level finder. Everything about the camera is mechanical and manual. What this means is I have to have a reference point for a particular level light. The reference point I use with the 160 speed film is an EV of 15 or sunny 16 rule or a starting point in full or slightly hazy sunlight. In other words I shoot a full or slightly hazy sunlight scene at 125 shutter speed and f/16 I "pull" the Fuji film 160 a little bit You use +/- EV values to overexpose/underexpose whatever your meter is reading. With the 160 film I "pull" it to 125 so it overexposes the film. If EV is negative you are underexposing...positive you are overexposing. If you push the film you are underexposing if you pull it you are overexposing it.

A big part of digital photography is ISO and white balance...this is the major component in any snap...and this why an understanding of EV and all of the rest is critical.

Eye-level said:

I big part of digital photography is ISO and white balance...this is the major component in any snap...and this why an understanding of EV and all of the rest is critical.

Click to expand...

I've been reading up and trying to understand EV but I many of the references I've been reading doesn't seem like the authors thoroughly understand or at least they're unable to explain it in a way that I can wrap my head around. It seems like they circle about the subject but don't fully explain it.

However, I've been thinking about EV and here's my take on it. It seems to me that the EV adjustment is simply a secondary fine tuning attenuation for the voltage coming from the sensor to the processor. And I believe this is why the effect is different than simply limiting the amount of light that reaches the sensor by way of shutter speed. Because in the case of increasing shutter speed and reducing the amount of photons that reach the sensor the secondary signal from the sensor to the processor would still have the same volume albeit less information. Again, almost like a volume knob on a high-end stereo... sorta.

So Jeff, is this even close to the way EV functions or no?

Yes it makes sense...sort of an "advanced" way of adjusting exposure through the sensor as opposed to the shutter or aperture. Makes even more sense than normal because the sensor is connected to a chip. Eg. you could probably more precisely control the light through the chip and thus fine tune the exposure to a high degree but in the end it still comes down to stops of light.

160 film at 125 is 1/3 stop overexposure...note how I am using the ISO to compensate the exposure instead of the aperture and shutterspeed... +1/3 EV... If it were a digital camera this would be the sensor. AND THIS IS WHY white balance should be thoroughly understood. WB decides what your snap "feels" like. White balance with film is just the type of film you use...(films are based upon temperature)

I like to shoot people so pulling the 160 tends to produce more detail in the highlight areas...this is also why I like how the Fuji S5 Pro sounds...it is supposedly great at controlling the highlights in portraits...

EV +/- on the D800 is based upon what is metered though I bet and perhaps the camera does do the compensation with the sensor/processor...check the exif...no shutter speed or aperture difference then the camera is making it up somewhere likely the sensor and/or processor itself.

If you move the EV only a click or two the suggested shutter speed, in M mode, does not change. But if you kick it down or a few more it will show you need to adjust shutter speed. But the thing is I can shoot an image at say 1/250 w/ EV= -1 and then another at 1/125 w/ EV = 0 and the two will not look the same. So EV changes produce something different than just limiting the amount of light on the sensor thru shutter speeds. That's why I was theorizing that it attenuates the voltage coming from sensor and before the CPU.

What does the exif say about the ISO on those two snaps?

Eye-level said:

What does the exif say about the ISO on those two snaps?

Click to expand...

Which two?

250 ev -1 & 125 ev 0

Eye-level said:

250 ev -1 & 125 ev 0

Click to expand...

Ahhh, Okay. Let me try to find them. I hope I didn't cull them.

Just found this and thought you might be interested.

Today Yanik Chauvin from Image-Y shares how he uses EV Compensation.
I’ve been using the EV (Exposure Value) button on my camera more than any of the other buttons so I thought I would share with you why and when I use it. Remember that I shoot with a Nikon so shutter speed and aperture are controlled with the front and back wheels not buttons

. But before I get into that, let me briefly explain to you WHAT the EV button is and what it does.
To put it simply, the EV button allows your to quickly underexpose (darken) or overexpose (brighten) your image. How it works is pretty simple. When you’re taking a photo, the camera’s job is to adjust itself by changing the shutter speed and/or apperture to properly expose your shot so that it’s not too bright or too dark. Some cameras do this better than others but that’s another story.

When you play with the EV button, what you’re doing is telling the camera to either brighten or darken the photo from the optimal exposure it perceives.

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You can use the EV button in P (programed auto), S or Tv (shutter priority) or A (aperture priority) modes.
In P mode, the camera will adjust the EV by changing the shutter speed and/or the apperture. In S/Tv mode, since you set the shutter speed manually, it will adjust the aperture to compensate. In A mode, the camera will change the shutter speed since you manually control the apperture.
NB: You cannot use the EV button to under or overexpose your photo in M (manual) mode since you control both the shutter speed and aperture manually.


Read more: EV Compensation Explained