Tagged: Sony 50mm f/1.8

Low Light Issues


I got a new lens … the Sony 50mm f/1.8 lens for my NEX-6.  The above is one of the first pictures I have taken with it.  This one at f/4.  I focused on the center of the flower … note the depth of focus, even at this aperture when used at its minimum focus distance.

I have found that for making pictures inside the buildings here that I have had the best results when using my Pentax K-5 and the Pentax 50mm f/1.8 lens.  My problem has been making pictures without flash or added lighting under conditions of poor lighting with mixed color temperatures from various sources.  Generally I have used the Pentax lens at f/2.5 which is wider than optimum for best sharpness but OK.  I ordered the Sony lens to see if I can squeeze a little more light out of it by using it at an aperture wider than 2.5.  If that works I will be able to use even a lower ISO setting with the NEX-6 camera and thus have less digital noise to remove.

There are three issues with getting good pictures in existing low light.  First, it helps to have a good prime lens with a wide aperture, but having a wide aperture lens isn’t good enough.  It has to be sharp at the wide open apertures.  With many lenses you have to stop them down before they become sharp enough.  Since I do a lot of crop-zooming it is imperative that the lens is sharp at a wide aperture.  That is why I really don’t use my Pentax at a wider aperture than 2.5 … it isn’t as sharp on up to 1.8.  I’m hoping that the Sony lens will be sharper at a wider aperture, but it will take a while to test it and compare it with the Pentax 50mm lens.

If the lens is sharp at wide enough apertures, the next issue is the depth of field (DoF).  Depending upon the distance of the subject, the DoF is quite shallow at the wide apertures.  I often run up against this limitation depending upon the conditions and having the wider apertures of the Sony lens will not be of much value for some uses.

The third issue is the ability of the camera at high ISO levels.  The more you boost the ISO the greater the noise in the image.  To some extent it can be removed with the software, in my case LR5.  The problem is that the greater the noise removal, the less detail in the image.  A major factor in the camera’s high ISO capability is the age of the sensor/camera design.  The more recent designs tend to have better electronics and software resulting in less noise.  The other factor is the size of the sensor … the larger the sensor the less sensor noise.

The combined noise — focal length issue is my biggest problem in making most of my pictures inside of buildings as well as in making pictures of nature details early and late on cloudy days.  Since I usually need the extra reach, I have resorted to my longest fast prime lens and crop-zooming; but it often isn’t long or fast enough.  This issue is weighing heavily upon my decisions relative to my next camera.  I think that I may have to go to a full-frame sensor camera if I really think the cost is worth it.  Another problem, other than cost, is the size and weight of full-frame lenses.  I would have to not only replace my cameras but also the lenses.  If I wish to continue to make pictures of wildlife, and other subjects requiring longer focal lengths, it gets quite expensive and heavy.  What I am trying to do is balance my needs for better low-light capability against the likelihood of what pictures I will be making in the future.

My options seem to be:

1) Go with two new camera systems (includes new lenses) … one with a smaller sensor for use with longer zoom lenses in better light, and one with a larger sensor and shorter focal lengths for poorer light.  This is the most expensive option.

2) Replace my current cameras with one new larger sensor camera and shorter focal lengths and give up making pictures with longer focal length lenses; i.e. limited by ability to crop-zoom.

3) Some mix of new and current systems.

4) Use the cameras and lenses I have and work within their limitations.  This is the no future cost option and why I got the Sony 50mm lens.  I’m going to see how I do with it and use the time to wait and see what happens in the camera industry.

ADDENDUM:  I checked out the Sony 50mm f/1.8 at the wide aperture.  It is fine.  I saw no objectionable change in resolution/sharpness at ISO = 1000 vs. aperture of 5.6 with ISO – 3200.  I’ll now be using the NEX-6 with it rather than the K-5 with its 50mm f1.8 lens when making pictures indoors.