Low light lens vs using Flash

[xtra12]

Okay, so I am rather new to the serious photography world. I have a Nikon D5100 and seriously love it. I've purchased a couple of low light F1.8 lenses and those have been fantastic. I also purchased a larger flash for the top, but honestly haven't used it.

I guess because I'm new to the world, I don't know the advantages of using the flash instead of just a low light lens. The F 1.8 seems to be able to take photos in any environment. I know once I start incorporating a flash there will be a big learning curve with where to aim, settings, etc... (The photos I've practiced on have been seriously blown out.)

What are the advantages to using a flash instead of just a low light lens? I know I see most serious photographers, although I'm sure they have low light lenses, use flash for most purposes.

 

[astroNikon]

A "low light" lens allows more light to the sensor due to the larger aperture opening.

BUT the larger aperture opening also affects the Depth of Field (making it much shallower) =>Understanding Depth of Field in Photography

At some point in your photo, you may want a specific Depth of Field / Aperture

Also, at some point you may not want a slower Shutter Speed due to any type of movement.

Also, your camera's ISO may be limited to your criteria.

Thus at some point you may be limited to the Shutter, Aperture and ISO for the specific image you want to shoot.

and if the photo is still too dark, then you have to add more light.
Thus you add a flash or other alternative light source.

OR, you adjust ISO / Aperture /Shutter beyond what you wanted and deal with the consequences/ results.

Adding light, from a flash or other source, allows you to keep your Aperture, Shutter and ISO well within the "bounds" where you want a good photo. It also allows you to light up the details, shadows and give depth to a photo (if used properly). There's a lot to learn in using a flash. Here's a starting point ==> Strobist

 

[astroNikon]

Flash can help in many situations, but cannot help in other situations.

If you shooting someone one a bright day, but they are under a tree in the shade. You'll probably get the person in a good exposure but the background/sky would be totally blown out. The flash allows you to balance out the subject by adding light, to help the background not get blown out.

BUT
If you are in a low light situation such as many sports. either indoors or in the evening. You simply cannot use a flash (either too far or too fast action and simply not allowed). For indoor sports, etc you deal with your setting as you cannot slow down shutter too slow otherwise it will be blurry. too high an ISO introduces noise/grain. thus your equipment & experience really matters at that point.

 

[soufiej]

"What are the advantages to using a flash instead of just a low light lens?"


This is not an either/or situation in all cases. As suggested above, your lens has certain properties which relate to more than simply avoiding any supplemental light source.

You should first begin to study the exposure triangle which involves aperture, shutter speed and ISO (what would have been called our film speed prior to digital photography) as a three legged stool. If you remember back to high school physics class, three points define a plane and the plane will always try to seek its own level. So too will the three legs of the exposure triangle seek the proper exposure value.

By learning the triangle you will begin to see when you are able to use the widest aperture on your lens as a creative choice for picture style. In another situation you might resort to a faster/slower shutter speed or possibly raise the ISO to enable a closed down aperture (with a deeper in focus field) and a slower shutter speed.

Slower shutter speeds risk blurring of the subject though and ISO values (digital signal amplification) can only take you so far before increasing digital noise becomes problematic. It is at that point that you must begin to consider adding supplemental light sources. Flash is your most common form of supplemental light though not always your single best choice.



Alternatively, realize the simple fact your digital camera lacks the dynamic range of human perception. This can often lead the photographer to consider adding "fill light" from a supplemental source. Once again, flash is the most common source for this light.

Though there are multiple ways to obtain additional light in the deepest shadows of a subject, adding flash to your arsenal of tools is a quite common technique. Place "how to use fill flash" in a search engine for ideas about the use of flash as a supplement to full daylight conditions. Additionally, any back lit subject might benefit from a bit of supplemental light.



Stepping indoors will cut your available natural light by dramatic amounts. Now, inside even a well lit room you must make your decisions as to where you will gain the additional light sensitivity your camera requires for proper exposure.

You can raise ISO (noise) or slow shutter speed (blur) or even open up your lens aperture (shallow depth of field).

Each step you take will require you make further decisions about image quality. If you are shooting, say, a child's birthday party indoors, your options become more limited. Slower shutters will likely result in blurred images. Raised ISO values can add significant amounts of digital noise - or "grain" - to your photos. Wider apertures will result in a more shallow depth of field which will leave many subjects out of focus.

The answer here is most often to add your flash unit as supplemental light which gives you a bit of a fudge factor in your exposure settings.



So whether you are using your flash for the purpose of purely supplemental light which will allow you to keep your exposure settings at a reasonable point or you are adding supplemental light as a creative choice, you will need to learn to rules of using flash.

Your shots that appear to be blown out are the result of too much light falling on your subject. Your camera's menus have settings which will control the amount of light being output by the flash and exactly when during the shutter opening that light flash occurs.

More than likely though what you are seeing in your present shots is simply a matter of distance between your flash and your subject;