Help with fast prime lens please

piolet_rampe · January 19, 2011

Hello, I would really appreciate some feedback about my technique with my Canon EF 50mm 1.4 lens. Below is a link to a gallery where I have taken the same shot with each available stop starting at 1.4 and ending at 22. Taken with Canon 60D on tripod using aperture priority, auto iso, no flash, average indoor light conditions.

I have owned this lens for more than a year and have always attributed some of my poor shots to operator error, however now that I am reading more online, it seems that this lens (and other fast primes in general) gets inconsistent reviews. This reinforces my belief that it is my lack of knowledge in how to use the tool, rather than the tool itself. With many people claiming that it is a "sharp" lens, with good examples as evidence, I am now motivated to learn what I am doing wrong. I decided to run this experiment using existing light indoors since one of the main reasons I bought this lens in the first place was to be able to take low light pictures.

Please have a look at my gallery.

http://mountains2sea.smugmug.com/Other/test-shots-wCanon-EF-50mm-f14/15509724_fcTeK#1161685754_SaWBL

The shots aren't looking good in my opinion until about f4 or so, with the pictures at greater aperture looking very dreamy. I carefully focused as best I could on the shell in the center by zooming in on the screen. After about f5.6, the shutter speed compensates with slower settings, making anything beyond f5.6 unsuitable for hand held shots. Also, the iso has to compensate as well.

I have read that some people believe they have gotten a bad copy of the lens. I suppose this is always possible, but I certainly hope not since the warranty period has elapsed. I suspect I simply don't know what the natural limitations of this lens are.

Any tips please? Thanks.

SimpsonBrothers · January 19, 2011

The ISO not staying constand and using 1/3 stops is also killing your quality. I would recommend reshooting using a consistant ISO and let your speed change.

pathfinder · January 19, 2011

Or adding flash, rather than dealing with extending the shutter speed.

The depth of field at f1.4 is very thin, while at f16 it is significantly larger in your image, as is expected from optical theory.

I agree with the above poster, stick with a single ISO for lens evaluation images.

These don't look horrible, shooting at f1.4 is hard to do, with extremely shallow dof, and less sharpness than at 2 stops higher apertures, again, exactly as expected from Optical theory.

piolet_rampe · January 19, 2011

pathfinder wrote: »

Or adding flash, rather than dealing with extending the shutter speed.

The depth of field at f1.4 is very thin, while at f16 it is significantly larger in your image, as is expected from optical theory.

I agree with the above poster, stick with a single ISO for lens evaluation images.

These don't look horrible, shooting at f1.4 is hard to do, with extremely shallow dof, and less sharpness than at 2 stops higher apertures, again, exactly as expected from Optical theory.

some new ones.
http://mountains2sea.smugmug.com/Other/shells-400iso-w-flash/15516743_Do8Mo#1162218703_Nihn3

Thanks for the advice. I went back and shot some of the same picture, but used a 430ex flash, held the iso at either 400 (or 1600 for the statue). There is certainly improvement, and it seems that the sweet spot for this lens is around f2.8 - f5.6.

But.... my curiosity is specifically about the qualities of using f1.4. As you can see in my shots, f1.4 is pretty dreamy looking, with such a narrow DOF that using this for a portrait would result in a focused nose, but blurry eyes and ears.

What circumstances lend themselves to shooting in f1.4? Does anyone have a good example? Having invested in a lens that opens up this much, it is natural to want to use it at that setting to take full advantage of what it has to offer. Thank you.

adbsgicom · January 20, 2011

You need to get the focus point right. Focus on the eye, then the nose and everything behind is blurred and the eyes are sharp. Don't let the camera pick your focus point. At this shallow DOF, you also can't focus and recompose. You need to have the focus point where it needs to be and then crop as necessary in post.

SimpsonBrothers · January 20, 2011

Really depends on the distance from you to your subject:
5' away: .2" of focus
10' away: .6" of focus
20' away: 2.4' of focus
50' away: 15.6' of focus

piolet_rampe · January 20, 2011

SimpsonBrothers wrote: »

Really depends on the distance from you to your subject:
5' away: .2" of focus
10' away: .6" of focus
20' away: 2.4' of focus
50' away: 15.6' of focus

This is helpful. The shots I have in that gallery are all at less than 2 feet away, meaning that the 50mm 1.4 EF (at f1.4) is likely not the right lens for such a shot. A larger subject, taken from 5' to 10' away may be a better subject when shooting at f1.4.

For this particular shot, I'll bet I would get better results with the EF-S 60mm, or an 85mm 1.8, or even one of the 100mm primes. Because the subjects of these shots are small items, I am kind of asking this lens to do the work of a macro lens it seems.

Thanks for the help everyone!

SimpsonBrothers · January 20, 2011

piolet_rampe wrote: »

...meaning that the 50mm 1.4 EF (at f1.4) is likely not the right lens for such a shot.

No, it can be the right lens, just not at that aperature.
Try it again at f11 and see what happens.

adbsgicom · January 20, 2011

Bear in mind that if you are using a 50mm lens at 2', then a 100mm lens at 4' is about the same DOF.
On a 5D (full frame)
50mm f/2.8 @ 2' = 0.91" total DOF
100mm f/2.8 @ 4' = 0.91" total DOF

SimpsonBrothers · January 20, 2011

Here is an example of 50mm set at f1.8 at 3' away:

and at 5'

piolet_rampe · January 20, 2011

SimpsonBrothers wrote: »

No, it can be the right lens, just not at that aperature.
Try it again at f11 and see what happens.

Yes, you are correct, the shots that are stopped down look sharp and are higher quality in this example. The nature of my inquiry however is more along the lines of "What the heck can I use f1.4 for now that I own a lens with this capability?" The nice shot above with the baby is a perfect example. I think more than other lenses / settings, this type of wide open shot requires a tripod. Hand held shots at 1.4 or 1.8 are going to be difficult to do.

pathfinder · January 20, 2011

Yes, shooting at f1.4 requires careful execution of focus, with or without autofocus.....

One of the main reasons for having an f1.4 lens is that it gathers so much more light in dim situations, it allows your camera to autofocus in light that an f4 lens will not AF at. Even if you shoot your f1.4 lens at f8.

The iris does not does not close down until the instant you press the shutter.

divamum · January 21, 2011

adbsgicom wrote: »

You need to get the focus point right. Focus on the eye, then the nose and everything behind is blurred and the eyes are sharp. Don't let the camera pick your focus point. At this shallow DOF, you also can't focus and recompose. You need to have the focus point where it needs to be and then crop as necessary in post.

+++1

I think this is far more important at wide apertures than a tripod (assuming your shutter speed is high enough and dependent on subject matter, of course).

Use singlepoint af and choose the appropriate one for the composition - for portraits, carefully place it on an eye or bridge of nose for maximum sharpness in the eyes (bearing in mind that if the head is turned you may not be able to keep both eyes in sharp focus if the head is turned even slightyly). Also, when shooting shallow dof, be prepared for more duds than you might get stopped down, and shoot accordingly.

Help with fast prime lens please

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