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Old Mar 28, 2005, 2:25 PM   #1
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The old 1/ASA (1/ISO) at F16 for bright Sunlight, does not seem to work for me using a digital camera. Is there a new formula for Digital cameras? I own a Nikon D70.



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Old Mar 28, 2005, 2:52 PM   #2
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I could be mistaken, but I thought the sunny 16 rule was used to calibrate light meters.


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Old Mar 28, 2005, 3:03 PM   #3
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Maybe that also, but I use for exposure for pictures. Bright Sun f16, cloudy down one F-stop, in the shade down 2 f-stops all at 1/ASA for Sutter Speed...... Thats How have used it seemed to work well for me with film. All that went down the tubes using my Digital Camera.



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Old Mar 28, 2005, 4:01 PM   #4
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Those rules should be equaly valid for digital as they are for film. Those numbers quantify a particular amount of light. That is the same in ANY camera or lens. If you have the forumla correct (I am not familiar with it) then something is wrong with the camera. For that formula to work, the camera must be in manual exposure mode. I don't know if exposure compensation affects manual mode but just in case make sure it is set to zero. Make sure your ISO is not set to auto. What are the specs of your lens. The lens must be capable of operating in the range of values that you are using in your formula. Do you have any filters on the front of the lens (other than uv). If so, remove them. Make sure the builtin flash is closed.

If all seems OK, then you should probably take the camera into a repair shop and have the ISO and shutter speed calibration checked.

I hope this is of some help.

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Old Mar 28, 2005, 5:24 PM   #5
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jsaenz wrote:
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The old 1/ASA (1/ISO) at F16 for bright Sunlight, does not seem to work for me using a digital camera. Is there a new formula for Digital cameras? I own a Nikon D70.
That should get you pretty close. What problems are you having (overexposure, underexposure)? By how much?

Does the camera's meter indicate the under or over exposure when you're using manual exposure mode?

One thing to keep in mind is that Dynamic Range with Digital is notgoing to be as wide as with negative film.

So, even though the Sunny 16ruleworked with film, you had more exposure latitude with film.

Shooting Digital is morelikeshooting color slides. You want to expose for the highlights, with exposure accuracy becoming more critical.



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Old Mar 28, 2005, 9:23 PM   #6
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jsaenz wrote:
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Maybe that also, but I use for exposure for pictures. Bright Sun f16, cloudy down one F-stop, in the shade down 2 f-stops¬* all at 1/ASA¬* for Sutter Speed...... Thats How have used it seemed to work well for me with film. All that went down the tubes using my Digital Camera.

¬*

-jorge

¬*
The 'sunny-16' rule still works with digital cameras; the problem is that some (most?) digital cameras are not held to any standard for calibrating the ISO value that is offered by the metering system. For example on the same bright sunny day (two hours after sun rise, which is the standard for which the rule applies) both my Luna Pro and Sekonic L358 light meter showed 'dead-on' 1/100sec at f16 for ISO 100, yet my Minolta A1 reported 1/160 sec for f16.

In Minolta circles, as with several review sites, it is well known that the A1 has a sensor that is ~2/3 stop more sensetive than advertised. My data supports this claim.

My guess is that this sort of variance is not unique to the Minolta A1.

My old Oly C3020 ISO is slow by ~1/3 stop using the same experimental process.

None of this matters if you stick with the camera's metering system determining the exposure (assuming that the metering system of your camera is self consistent). The only disconnect is when you want to use manual exposure settings.

When I am using my A1 set at ISO 100, for example, I dial in ISO 160 on my Sekonic and the A1 manuallly set exposure as determined by theSekonic is spot on.

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Old Mar 28, 2005, 11:54 PM   #7
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I thought this thread might be about taking pics in a Fighter Jet when I clicked on it.

I'm embarrassed.

It shows how green I am.
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Old Mar 29, 2005, 6:37 AM   #8
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I the camera is set to manual, but the ISO is set to Auto. There are no filters on the lenes. There is no compensations set on the camera. The pictures are I am getting are underexposed. I will change the Auto ISO Settings on the camera, and give it another shoot.



Thanks for all your help, I will try it and get back to you.



-jsaenz


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Old Mar 29, 2005, 7:46 AM   #9
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Get an EXIF reader so you can see what your settings were: they aren't always what you remember them to be.
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Old Mar 29, 2005, 8:59 AM   #10
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Quote:
I the camera is set to manual, but the ISO is set to Auto. There are no filters on the lenes. There is no compensations set on the camera. The pictures are I am getting are underexposed. I will change the Auto ISO Settings on the camera, and give it another shoot.
You are aware that the camera starts out at ISO 200 (not ISO 100), right?

In any event, if the camera used a higher ISO speed than you think it's using, your photos would be overexposed, not underexposed (and you say your problem is underexposed images).

I looked through some D70 photos, and from what I can tell,it should be pretty accurate with it's ISO speedrating.

For example, this photo was taken at ISO 200, f/11, and 1/500 second:

http://www.steves-digicams.com/2004_...s/dsc_1393.jpg

This is exactly what I would expect if lighting was at an EV of 15 (typical for this type of scene). In other words, you would have gotten about the same exposure using ISO 200, f/16 and 1/250 second (slightly faster shutter speed compared to using the Sunny 16 rule of thumb). IOW, the scene would have been exposed slightly brighter if you followed the Sunny 16 rule in this example (the opposite of the problem you're having).

Here is another image that was taken at ISO 200, f/5 and 1/2000 second. This is what I'd expect of the lighting was slightly less than EV 15.

http://www.steves-digicams.com/2004_...s/dsc_0521.jpg

The human eye adjusts well to variations in lighting. So, you may be assuming that light levels are at EV 15, when they're really at EV 13 (which would underexpose by 2 stops using the Sunny 16 rule of thumb). With film, you may not have noticed these variations, since the labs are compensating for it, and negative film has a wider dynamic range compared to Digital.

You may also be seeing a variation in the lenses you're using -- where the stated aperture is not totally accurate at all focal lengths.

Your best bet to insure accurately exposed photos is to use the meter built into your camera (which will tell you how much your settings vary from what the camera's metering believes is correct). Simply center the needle for most scenes (depending on the metering type selected, this is probably going to work well most of the time). You can then check theimage's exposureusing the camera's histogram to see if you got it right, or need to reshoot it with different settings.

Or, if your goal is controlling Depth of Field, shoot in Aperture Priority (Av) Mode, and let the camera select the appropriate shutter speed for the shot.

I know where there is a gallery of D70 images that include meter readings, as well as camera settings. But, it's down right this minute.

When it's back up, I'll take a closer look to see if there is a variation between the metered light, and the camera settings used, that would indicate the camera's ISO sensitivity is not accurate. But, I suspect that it's probably "spot on", and you're just seeing a variation in lighting.


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