How do I change the lens opening when the samera is on the manual mode. I swtch to manual and can change the shutter speed, but not the lens opening. Can you mail me a user manual to desccribe these techniques

Set the exposure mode to "M" (Manual). You'll have to set both the aperture and shutter speed yourself.

You'll also get no exposure assistance from the camera's light meter. You can review the picture after taking one and/or use the histogram to tune the exposure.

M stands for 'Manual mode'. This is the mode wherein you set your shutter speed and aperture setting. A stands for 'Aperture Priority'. This is the mode where you set the aperture or opening of the lens and the camera sets the shutter speed. The lower the aperture number setting, the more light penetrates the lens, a faster shutter speed is needed. This setting is usually used for portrait scenarios. S stands for 'Shutter priority'. This is the mode where you set the shutter speed and the camera sets the aperture. The higher shutter speed number, the lower aperture number is set by the camera to accommodate more light into the lens. This setting is usually used for capturing moving objects like cars. P stands for 'Program Mode'. The camera takes care of different settings except for the aperture and the shutter speed. You get to choose combinations of aperture and shutter speed settings that will not change the exposure of your scene. This is like a combined 'A' and 'S' mode with different combinations. N stands for 'Natural Light'. The camera tries to make use of available light. This is ideal for indoor use when flash is prohibited or when you just want to capture the ambiance of the scene. The camera sets a high sensitivity setting to handle low light conditions. The drawback of this would be grainier pictures. SP1 and SP2 stand for Scene Position 1 and 2. This is like a memory setting for most commonly used scene settings. For example, you can assign SP1 for landscape mode scene and SP2 for night mode scene. You have 13 scenes to choose from in your camera, 2 of which you can assign in SP1 or SP2. The default setting for SP1 is Portrait mode and for SP2, it is Landscape mode.
Hope this helps.

I'd say you're severely underexposing. The M mode is for manual exposure. This means you're responsible for setting the appropriate shutter speed and aperture. The aperture controls how much light passes through the lens, the shutter speed controls how long that light hits the sensor. The two of them have to be adjusted properly to suit the amount of light hitting the subject. If the lens doesn't admit enough light and/or the shutter is opened for too short an amount of time, not enough light gets to the sensor and you get a black image.

The S mode is for shutter priority. This lets you set the shutter speed and the camera automatically adjusts the lens aperture for correct exposure. However, the lens has a maximum aperture beyond which it cannot open. If the shutter speed is too fast, again not enough light gets through the lens and you get a black image.

Since you didn't specify the model of your Nikon camera, I can't tell you exactly how to adjust the shutter speed and aperture. If you can't find the procedure in your manual, please feel free to reply to this post, specifying the model.

Once you're in the P mode, turning the command dial will change the shutter speed and aperture in opposite directions to maintain the same exposure (within the limits of the camera and the lens). You should see the shutter speed in the viewfinder change.

If you want absolute control of the shutter speed, change to the S mode. The command dial will then allow you to control the shutter speed, and the camera will automatically change the aperture to compensate (again, within the limits of the lens).

Proper exposure is a balancing act between the shutter speed and the aperture (the size of the opening in the lens). (There's also the ISO sensitivity, but I'll ignore that for now.) If the shutter is open for a longer time, the lens must be closed down. If the shutter is open for a shorter time, the lens must be opened up wider to allow the same amount of light to reach the sensor.

The Shutter priority mode attempts to adjust the aperture to give the proper exposure for the shutter speed you've selected. The lens has physical limits as to how wide the opening can be. If the shutter speed is too fast, the lens will only open as far as it can go but that may not be enough. In this case the camera will display "Lo" in the viewfinder to warn you but will go ahead and take the picture anyway. If the shutter speed is too fast then you won't get enough light through the lens and you'll end up with a dark or black picture.

Try reducing the shutter speed (leaving it open for a longer time), like 1/30 of a second instead of 1/125 of a second. If the shutter is open too long, you run the risk of camera motion. You can also increase the ISO setting, making the sensor more sensitive to light. This increases digital noise, which looks somewhat like film grain. You can also try adding more light, perhaps by using the flash, if the subject isn't too far from the camera.

You have described Aperture priority mode: you set the f/stop and the shutter speed changes to make the exposure correct.

Full manual mode requires you to set both the shutter speed and the f/stop. You are seeing the recommended f/stop for the shutter speed you have selected.

According to what you say, it seems that you selected B (Bulb) as shutter speed (and MANUAL mode).

First, check whether you are on MANUAL mode ("M"); then, check your shutter speed. If it's really in "bulb" mode, all you have to do is dialing the speed button down to figures that match your subject's light conditions and your other preferences involved in the exposure (ISO, lens apperture).

Quite right too. When the M42 adaptor is fitted there is absolutely no exchange of information between the lens and the body: M42 lenses pre-date all of those later developments. Your camera will also be unable to stop down the lens automatically when taking the picture, most M42 lenses don't even stop down automatically when connected to an M42 body.

You need to do things the old-fashioned way. Your camera needs to be set to meter manually, shutter priority mode may also be used. In manual mode you focus the lens as normal with the aperture ring set to the lowest aperture number (i.e.aperture is wide open).
You then make sure that the lens in in manual mode as well and stop down to whatever you want, if the image remains bright enough then you can adjust the precise focus using the hyperfocal principle if you like which takes advantage of the increased depth of field of a stopped down lens.
In manual mode, you then tell the camera what aperture you have set (read it from the lens barrel) and set the shutter speed using the camera's light meter to guide you. If using shutter priority mode then the camera will choose the shutter speed for you.
Check everything is set as you intend and press the shutter.

It all sounds long winded but is exactly how many of the world's greatest photos were taken and soon becomes second nature. You also learn far more about the relationship between aperture, shutter speed and ISO settings and will be able to talk about reciprocity like you know about it!

I have two possible solutions:

First, are you shooting with the flash up or an external flash connected to it? If so, the camera likely needs to synchronize at 1/200 or slower otherwise it won't be able to take a full photo. As a safety feature to prevent that, many new cameras just restrict the ability to pick a faster shutter speed.

Second, if its not related to the flash, it might be related to the mode you are using. Turn the camera off the automatic modes and put it on an all manual setting. Change the ISO to 400 or so, got outside and aim up at the day's sky, put it on manual mode and then adjust the shutter speed. Open up the aperture on your lens all the way (turn it to the smallest number). Now adjust the shutter speeds. It should be able to go past 200 now.