Hi everyone, I recently purchased a D50 along w/ a Sigma 18-125. I'm pretty new to dSLRs, however I'm not a complete beginner to photography and I've done share of homework regarding how to use the D50 properly. This is my question:

I understand under certain situations, the meter can be uncertain and display "Lo" or "Hi".

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I'm wondering if there's a way to see the shutter speed despite this?
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Also, I'm baffled at why (having "about" the same settings: metering, ISO, exposure mode, etc.) my 2 P&S cameras (Canon A510 & Casio Z120) ae able to meter the same scene fine, while the D50 gives me the "Lo" message (the scene is pretty dark).

I've posted this at another forum ( http://www.megapixel.net/phpBB2/viewtopic.php?p=34076 ), but I'm looking to get more helpful answers from actual Nikon users here. Any help would be greatly appreciated. Thanks!

There isn't enough light to meter. I'm guessing too that the lens on your D50 has a smaller maximum aperture (bigger number) than do your P&S. Your Canon goes to f/2.6 while the Signma lens is no faster than f/3.5.

Bob Johnson - Earthbound Light - Nikonians Gallery
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Thank you for your reply, bobj. Yes, the max aperture on the Sigma lens is 3.5, while that of the Canon is 2.6 and 2.8 for the Casio. Now, if I decrease the aperture on the P&S cams to 3.5, would that even things up? If so, the P&S cams are still able to meter the scene.

Your D50 is still metering the scene, it just isn't telling you what it is setting

No, that won't work. Metering always happens with the lens fully open. It only stops down to your selected aperture when actually taking the picture.

Bob Johnson - Earthbound Light - Nikonians Gallery
Nature Photography from the Pacific Northwest and beyond
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3.5 on a P&S and 3.5 on a dSLR are not the same. 3.5 on a P&S is the equlivent of about f/14.

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Eh??????

No, aperture is defined as the effective diameter of the hole divided by the focal length, regardless of lens and regardless of sensor size.

You are undoubtedly thinking about the fact that depth of field differs, but this is because the sensor size differs, and has nothing to do with aperture.

Edited to correct typo: aperture is focal lenth divided by diameter, not the other way around. Ooops.

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Focal length's on fixed-lens digital camera's are also different than 35mm film and digital slr camera's. Most are listed as something like 7-21mm or 9-72 or something similar. 9-72mm is the equlivent of 35-280mm.

Therefore if the focal length is different, then since aperture is based on a calculation with focal length, aperture will also be different.

If I took a picture from about 8 feet with a flash and the shutter was 1/60 and aperture was 2.8, focal length used was 36mm it would probably be overexposed. But with a fixed-lens digital that 36mm focal length is actually 7.1mm. So at 1/60 with f/2.8 it is exposed correctly.

With a fixed-lens digital, if 2.8 is the equilivent of f/11 on an slr. Then at 36mm 1/60 with f/11 with a flash is about right.

You may or may not have noticed that most fixed-lens digital camera's have apertures that go past f/11.

Its also pretty difficult to not have a deep depth of field with a fixed-lens digial.

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No, exposure is exposure and aperture is aperture. And focal length it focal length. And of course shutter speed is shutter speed. The size of the sensor has nothing to do with exposure.

Bob Johnson - Earthbound Light - Nikonians Gallery
Nature Photography from the Pacific Northwest and beyond
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Sorry to be a nit-picker, but the relationship is the other way around, focal length divided by the effective diameter - the 'official' notation is f/#, i.e. focal length divided by the f-number. So, as the hole gets smaller, the f-number gets bigger. It goes in strange looking steps (1, 1.4, 2, 2.8, 4 etc.) because the amount of light admitted is what we're interested in, and so dividing the diameter by (about) 1.4 actually halves the area of the hole, and therefore the amount of light admitted. That's the science lesson over.

Easy to see why P&S camera apertures stop at f/11 - that's a hole about 2/3 of a millimetre in diameter in a 7mm lens.

But yes, Bob, I agree with your aperture is aperture etc. post. We don't fuss about the focal length in use when using the Sunny 16 rule. And as I recall that rule works for large and medium-format as well as 35mm and Digital SLRs. Why it should be any different for small format cameras escapes me.

Chris

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Ooops, a typo. Thanks for catching this.

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As I understand it, Lo & Hi indicate that the camera cannot set a shutter speed slow or fast enough for correct exposure. 'Hi' is obvious enough, the camera is physically unable to go beyond 1/4000. But where will the meter stop at the other end? I just did a quick and crude experiment, and I'm guessing at 1s. In Shutter Priority, the aperture gets replaced by Lo or Hi if the camera can't set a suitable aperture.

Maybe the P&S cameras aren't being entirely truthful, and are simply setting widest aperture & slowest shutter, and hoping for the best?

Hope this helps,
Chris

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...
>Maybe the P&S cameras aren't being entirely truthful, and
>are simply setting widest aperture & slowest shutter, and
>hoping for the best?
>
This is basically whats happening. The P&S cameras don't tell the user "scary stuff". Nikon's DSLR's, on the other hand, will warn the user, by displaying "Lo", that the light is too dim for the camera to meter accurately. This is not to say that the camera won't be able to shoot. It will use its best guess, as the P&S cameras do, if you take the picture.

Also, meter cells in SLRs, digital or film, are at a great disadvantage to other metering systems when it comes to low light sensitivity. They only see light coming in through the lens and that light must be shared with the VF and the AF system. Only a small fraction of the light can be split off for the meter cells as most of it is needed for the VF. Combine this with a relatively slow f/3.5 or so lens and you really have a challenge getting decent low light sensitivity.

-----
dwig
nikonian in paradise
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use: cp8400, cp990, cp950
retired: F,ELW, 21mm, 45 f/2.8 GN
used to own: S2, SP, F2, F3, 20mm f/3.5, 35mm f/1.4, 35mm f/2.8, 43-86 f/3.5, 50mm f/2, 50 f/1.4 (for S2/SP), 55mm f/3.5 Micro, 105mm f/2.5, 105mm f/4 Micro, 300mm f/4.5, 180mm f/4.5 (for 4x5)

As far as I understand it the "lo" displayed in the viewfinder is just a warning about handholding the camera. I have only seen this using any of the program modes. When in a low light situation and the camera shows "lo" switch to manual. The camera can definately still meter the scene. Even if you take a photo with the "lo" message in the viewfinder, the camera will still use the proper exposure. It just doesnt tell you what it is while in a program mode.

Nikon D50
18-55 Kit Lens
50mm 1.8 AF
75-240 AF

A big THANK YOU to everyone who's replied and offered advice, I really appreciate it!

And yes, if I get Hi or Lo, I can still go into full Manual mode and the meter will work, although it'll "blink", I guess as a warning to possible inaccurate metering. Also, I can get a "Lo" warning even if the shutter speed is within reasonable range, ie. 1/1.6s.

I just wanted to post this just to see if its a problem with the camera's meter, because I still have time to exchange it for a new one. But it from reading the comments here, that doesn't seem like the case.

If there's more suggestions, please share. Again, thank you.