New to D50, questions about modes

[colemanr]

I'm new to photography, and I just purchased a D50 and 18-70mm/F3.5-4.5 lens. I'm still feeling my way around the different settings, and I'm noticing a couple of things that I didn't expect.

First, if I'm taking indoor, flash pictures in "Aperture Priority" mode, it looks like the slowest shutter speed that the camera will select is 1/60s. Based on the exposure meter in the eyepiece, the picture will be underexposed for every single f-stop that I choose, F3.5-F22 (the bars fill the "-" side of the meter), so I don't understand why it won't slow down the exposure to correct it.

On the other hand, in the same scene, if I choose "Shutter Priority" and crank down the shutter speed to 1/4s, the camera chooses F3.5 with proper exposure. Why does the camera not choose a slower shutter speed in AP mode?

Second, in "Program" mode, sometimes the exposure compensation control seems to allow me to continue to increase or decrease the desired EV, even if there's no apparent change to the shutter speed, aperture, or ISO values. For instance, I'll start with the camera's choice of shutter and aperture and the camera will pop up the "program modified" icon no matter which way I adjust the exposure, without any noticeable change in the parameters. It even keeps track of the number of "clicks" that I moved the dial and requires the same number to return to normal.

In other cases, I've had it respond "properly" and offer me alternative parameters, so I'm left wondering if, when it doesn't appear to change anything, it's just changing something that I can't see.

"Program" mode also seems to limit me to 1/60s shutter speed, so I suppose that's just another indication that it's just a good idea.

I appreciate any advice,
Rob

[erichlund]

Well, I haven't figured out the second one, but I tried the first one with my D200 and got the same result. In aperture priority and flash, the slowest the shutter will go is 1/60. So, if you don't use a wide enough aperture, you will underexpose the photo. I don't know if it's just a Nikon thing, but it doesn't appear that your meter is somehow broken. It may be that 1/60 is the slowest automatic flash aperture.

[colemanr]

Thanks for the reply. At least that's independent verification with a much more expensive camera. I can get the exposure I'm looking for with shutter priority, so it's not a big deal.

As far as the second question, I apologize if my description was a little convoluted. Here's a simpler example:

Turn on the camera indoors without the flash. Set it to "program" mode and use the "command" dial to select alternative aperture/shutter combinations with the same exposure. Each click of the dial away from "normal" causes an icon to appear (P*) on the camera's top display. In some cases, I can see the aperture and shutter speeds changing when I rotate the dial, but other times it appears that nothing changes. Even when I see no apparent changes to the shutter or aperature, the camera lights the "P*" icon, presumably to indicate that the settings are no longer what it selected.

In these cases, is the camera adjusting some other parameter that isn't displayed? I've turned "ISO Auto" off, so I know it's not adjusting ISO.

Thanks,
Rob

[erichlund]

Thanks for the reply. At least that's independent verification with a much more expensive camera. I can get the exposure I'm looking for with shutter priority, so it's not a big deal.

As far as the second question, I apologize if my description was a little convoluted. Here's a simpler example:

Turn on the camera indoors without the flash. Set it to "program" mode and use the "command" dial to select alternative aperture/shutter combinations with the same exposure. Each click of the dial away from "normal" causes an icon to appear (P*) on the camera's top display. In some cases, I can see the aperture and shutter speeds changing when I rotate the dial, but other times it appears that nothing changes. Even when I see no apparent changes to the shutter or aperature, the camera lights the "P*" icon, presumably to indicate that the settings are no longer what it selected.

In these cases, is the camera adjusting some other parameter that isn't displayed? I've turned "ISO Auto" off, so I know it's not adjusting ISO.

Thanks,
Rob
OK, My wife and I were going out dancing, so I didn't have time to mess with the second item then. (Never keep a lady waiting. That's the most important information I can convey in this post. :) ) There's a very simple answer to your question. As you hold the shutter half down and rotate the command dial, it changes to alternate exposures. When the numbers stop changing, it is because you have reached the f stop limit at either end. It cannot change any farther because this mode always provides an equivalent exposure to the basic P mode exposure, so if you change exposure time, you also have to be able to change exposure f stop to compensate.

Try this. With the lens set full wide, use the flexible program mode (this is what you were doing) to set the smallest possible aperture. On my 18-200, that is f/20. Now, while holding the half shutter, zoom to full telephoto. My aperture changes to f/32. Just a simple little illustrative exercise that has no real meaning at all, except you learn something about how your camera behaves. BTW: The 18-70 may have the same smallest f-stop both wide and tele, so you may not see any change.

[colemanr]

OK, My wife and I were going out dancing, so I didn't have time to mess with the second item then. (Never keep a lady waiting. That's the most important information I can convey in this post. :) ) There's a very simple answer to your question. As you hold the shutter half down and rotate the command dial, it changes to alternate exposures. When the numbers stop changing, it is because you have reached the f stop limit at either end. It cannot change any farther because this mode always provides an equivalent exposure to the basic P mode exposure, so if you change exposure time, you also have to be able to change exposure f stop to compensate.

Try this. With the lens set full wide, use the flexible program mode (this is what you were doing) to set the smallest possible aperture. On my 18-200, that is f/20. Now, while holding the half shutter, zoom to full telephoto. My aperture changes to f/32. Just a simple little illustrative exercise that has no real meaning at all, except you learn something about how your camera behaves. BTW: The 18-70 may have the same smallest f-stop both wide and tele, so you may not see any change.

Thanks for that explanation, that makes sense. You're right that I've reached the f-stop limit of my lens when the numbers stop changing, but I found it odd that the camera doesn't simply ignore my attempts to continue clicking the dial in that direction. It still acts as though it's increasing or decreasing the exposure (by popping up the icon), but I don't think it's actually *doing* anything.

Perhaps, based on your example, it's allowing me to request a certain amount of over- or under-exposure, even though my current zoom setting (and corresponding f-stop range) won't allow for it. Adjusting the zoom may "expose" additional f-stops, and the camera would automatically shift the settings.

By the way, my lens supports f/3.5 at 18mm and f/4.5 at 70mm, so I do see what you mean.

Thanks, that was very helpful.

Rob

[erichlund]

Thanks for that explanation, that makes sense. You're right that I've reached the f-stop limit of my lens when the numbers stop changing, but I found it odd that the camera doesn't simply ignore my attempts to continue clicking the dial in that direction. It still acts as though it's increasing or decreasing the exposure (by popping up the icon), but I don't think it's actually *doing* anything.

Perhaps, based on your example, it's allowing me to request a certain amount of over- or under-exposure, even though my current zoom setting (and corresponding f-stop range) won't allow for it. Adjusting the zoom may "expose" additional f-stops, and the camera would automatically shift the settings.

By the way, my lens supports f/3.5 at 18mm and f/4.5 at 70mm, so I do see what you mean.

Thanks, that was very helpful.

Rob
No, it's really much simpler than that. The code that causes it to do that pop, as you call it, happens with every click of the wheel, whether or not there is a change. That keeps the code simpler, so it takes less space. Cameras are computers, but they are very small computers, so space to store code is at a premium. Why change a behavior if it's going to take up space and not make a significant contribution to the operation of the camera?

[colemanr]

No, it's really much simpler than that. The code that causes it to do that pop, as you call it, happens with every click of the wheel, whether or not there is a change. That keeps the code simpler, so it takes less space. Cameras are computers, but they are very small computers, so space to store code is at a premium. Why change a behavior if it's going to take up space and not make a significant contribution to the operation of the camera?

Fair enough. I was willing to give Nikon the benefit of the doubt and also thought that perhaps there was another mechanism by which the exposure was being modified. It sounds like that's not the case.

Thanks for your help,
Rob

[goletitout]

I know the first problem with the 1/60 of a second in AV mode. I think it doesn´t matter that much. My shots are NOT underexposed, at least if my subjects are not that far away. I your subjects are only 1-2 meters away, you can safely use the 1/60 of a second. Some of my portrait shots have even been overexposed using that setting ! But if your subject is 3 or more meters away, yes, it will underexpose in dim light.

[goletitout]

I´ve made some new discoveries with the exposure. I´ve set to AV mode f7,1 and the cam automatically took 1/60s exposure time, as nearly always in AV mode when using flash. Then I set the flash power to +3 and took a shot of subject 3 or 4 meters away. They were totally overexposed, although the cam had still indicated that the shot would be totally underexposed.
I assume that the cam doesn´t include the expected flash power into its over- or underexposure calculation...I think the cam measures the over- or underexposure display ignoring the flash, as if you would take the given shot without flash. Clearly, with F7,1 and 1/60s without flash, the shot would have been very underexposed, but WITH flash, it simply wasn´t.

[colemanr]

Well, after a little sleuthing, I think I now understand why #1 happens (shutter pegged at 1/60 in low light and aperture/flexible program mode).

As far as I can tell, the flash on the D50 (and also, it seems, on some external flashes) can't or won't fire for a duration longer than 1/60 sec. This is why the camera always chooses at least 1/60 sec for the shutter speed when the flash is enabled and it's allowed to choose the speed (auto, aperture, flexible). Its goal is provide even flash illumination throughout the exposure, and it limits the shutter speed to allow that to happen.

When the shutter speed is decreased to less than 1/60 sec, some portion of the exposure will only be illuminated by ambient light. By forcing these slow shutter speeds in "S" and "M" modes, you're essentially determining how much ambient light you'd like to allow in after the flash finishes illuminating the scene.

Nikon actually calls this type of flash exposure "slow sync". If you hold down the flash button and spin the command dial, you can explicitly ask for "slow sync". This tells the camera that even in cases where it picks the shutter speed, you'd prefer longer exposures even if they let in additional ambient light. When "slow sync" is enabled, the camera appropriately chooses longer shutter speeds when necessary for proper exposure.

In those modes where the user sets the shutter speed, you're essentially using a back door method for enabling "slow sync".

This (http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00FJnP&tag=) is an interesting page and goes into this subject a little deeper.

Rob