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February 13, 2013
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I need some help with time exposures on auto.

:iconxenomorph1138:
xenomorph1138 Featured By Owner Feb 13, 2013  Hobbyist General Artist
First let me say that I'm just a hobbyist, and it's been quite some time since I've used my older SLR 35mm film format cameras (Pentax ME Super and Nikon F3), about 12 years). I recently bought a digital SLR, (Nikon D3100). With the older camera's, in "Auto" mode, on a tripod, for instance, if I was taking a night photo of a freeway to get the "river of lights effect", I used to be able to set aperture and shutter speed and the camera would choose the correct exposure time, let's say 8 seconds. With the digital cameras, I can't figure out how to do that. I can select a shutter speed or aperture but not both. Also with macro photos, there is the problem with depth of field, and to compensate I usually use a tripod and use the same method I described above resulting in a sharper, cleaner looking image.If someone could help me with this problem or point me in the right direction. If this is not the right forum, if anyone would care to share a couple of good sites with forums, I would be very grateful. Thank you for your help.

Baron
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:iconfallisphoto:
FallisPhoto Featured By Owner Feb 16, 2013
Cameras that can autoexpose can shoot in either aperture priority mode or shutter priority mode. Some have one mode, some have the other, some have both (but never both at the same time). With aperture priority, you select the aperture and the camera selects the shutter speed. With shutter speed priority, you select the shutter speed and the camera selects the aperture. To get the river of light effect that you are speaking of, you would select the shutter speed, which would be a long exposure, and the camera would select the aperture. Actually, that would not be the way to do it, but it might work. A better way to do it would be to do it in manual, where you select both aperture and shutter speed and the camera makes no decision at all. On a digital camera, the autoexposure modes are marked AV (aperture value) and TV (time value); there is also an "Auto" mode, but this is not truely auto, it just uses defaults. There are also some preset exposure modes, like "fireworks," "nightclub," and etcetera; these also use default settings -- for example, fireworks mode probably uses a time of  10 seconds and an aperture of f/16 (autoexposure is not involved). 
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:iconfallisphoto:
FallisPhoto Featured By Owner Feb 16, 2013

"I used to be able to set aperture and shutter speed and the camera would choose the correct exposure time, let's say 8 seconds."

 If you are selecting aperture and shutter speed, you are shooting in manual, not automatic. Your shutter speed is your exposure time. About exposure: There are only three adjustments that you can make: ISO, aperture and shutter speed. If you are using film, you usually set the ISO at the speed of the film, although you can adjust this to give an exposure that is slightly over or under if your shutter will only allow for whole stop adjustments. Otherwise, aperture and shutter speed are all there is to it. If you are selecting both, you are shooting in manual, because there is nothing else for the camera to select.

 

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:iconstevecaissie-stock:
SteveCaissie-stock Featured By Owner Feb 14, 2013  Professional Photographer
Also, for macros, there’s a program called Helicon Focus that can take a number of shallow-DOF photos with different focal planes and merge them into a single image with apparent “hyper-focus”. Invaluable for macros where you don’t want to introduce diffraction by exceeding your lens’ sweet spot.
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:iconxenomorph1138:
xenomorph1138 Featured By Owner Feb 14, 2013  Hobbyist General Artist
Yea, I realized that after I posted, and there is no edit. Actually I dug out my old ME Super and peered through the view finder and I saw the row of led lights on the left side with the exposure time next to each one (1/1000 - 1/60 - 8sec) and as I turned the aperture ring the exposure time would change depending on which direction I was turning the ring. I just explained it wrong. As I said, it's been 12 years or more since I picked up a 35mm. On top of that my memory isn't what it used to be. Anyway thanks for everyone's input.

Baron
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:iconstevecaissie-stock:
SteveCaissie-stock Featured By Owner Feb 15, 2013  Professional Photographer
Right there with you. My memory’s been going for years. I’ll be in the middle of a sentence and suddenly forget the most common word, like “salt” and my wife will roll her eyes while I sputter on for a few minutes trying to jar my brain back to work.

Have fun with the new camera.
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:iconxenomorph1138:
xenomorph1138 Featured By Owner Feb 15, 2013  Hobbyist General Artist
Thanks. :thumbsup::nod:
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:iconstevecaissie-stock:
SteveCaissie-stock Featured By Owner Feb 14, 2013  Professional Photographer
I think in your original post you must have meant to say, “...I used to be able to set aperture and ISO and the camera would choose the correct exposure time...”. The equivalent on a DSLR is to use Aperture Mode and manually set the ISO sensitivity.
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:icondrewzor:
drewzor Featured By Owner Feb 14, 2013
Some cameras will have a program mode, like pentax. It allows you to set either, iso, apature or shutter and auto compensate the other settings. So, change shutter to 30 seconds, it will set the best appature and iso for the light metered through the sensor. Its useful to use to learn the relationship between thesestting and before you know it, you wanting to go manual to push particular features. Like depth of feild, colour or motion blur.
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:icondrewzor:
drewzor Featured By Owner Feb 14, 2013
I should explain, this is different to say appature mode as it allows you to use your camera in manual like mode.
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:iconxenomorph1138:
xenomorph1138 Featured By Owner Feb 13, 2013  Hobbyist General Artist
Ok, I think I know what I was doing wrong. I'm just so used to the old SLR's. I suppose it's going to take a while to get to know my new camera. I would still be interested to know of some other recommended photography sites with forums. Thanks again.

Baron
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