F 1.8

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Archive 2009 · F 1.8

Ian Bower
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p.1 #1 · F 1.8

I am editing some photo's I took of my wife. (I will probably post them later if I am happy with them)

To shoot these photo's I used my 50mm 1.8 Wide open. Its really been my first test run with this lens since I got it...

This lens is supposed to be like - Spot on razor sharp focus. But all of the photographs seems out of focus. I shot all of them at 1.8

So my questions about shooting this wide open is...

Is it just such a narrow DOF that I couldn't possibly get her whole face into focus? should I shoot at a higher F stop for a Head and shoulder shot?

This is the only lens I have that opens that wide - so I'm not sure if this is a normal result.

I'm including one of the shots - Unedited, no WB adjustment or cropping. Tell me what you think of the focus.

Did I just miss?

Am I crazy and her face is in focus?

What happened?

Shot at f/2.5 50mm 1/60th

P.S. I realise I said I shot them all at 1.8 and this one is at 2.5 but humor me

Nov 05, 2009 at 11:39 PM

Steady Hand
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p.1 #2 · F 1.8

Ian,

We should talk.

I can explain it for you.

This is a common "user error" and nothing to worry about.

More later.

Nov 05, 2009 at 11:44 PM

Jim Rickards
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p.1 #3 · F 1.8

Lets do some calculations.
Find a good depth of field (DOF) calculator (google knows where)

Input the values -
-f stop,
-lens focal length and camera (so the crop factor can be figured out.)
-distance to subject.

The calculator will tell you:
-the total DOF
-the DOF in front of the focus point
-the DOF behind the focus point
Then you can look at your model and consider stuff like:
-how far is it from her eye (usual focus point) to
--her other eye
--her ear
--the hair behind her far eye.

After calculating all of the above you may decide:

- to choose a pose where both eyes are the same distance from the camera or almost the same to keep them sharp.

- to choose to keep the necklace blurred or sharp.

There lots to decide. A look at the calculator will be a good start.

Nov 05, 2009 at 11:59 PM

kakomu
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p.1 #4 · F 1.8

Ian Bower wrote:Is it just such a narrow DOF that I couldn't possibly get her whole face into focus? should I shoot at a higher F stop for a Head and shoulder shot?
This is probably the biggest issue. At f/1.8, the DoF is very narrow requiring you to shoot straight on to get the whole face in focus. If the person is tilting their head, you'll see the effects of a narrow DoF very easily.

Nov 06, 2009 at 12:20 AM

Ian Bower
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p.1 #5 · F 1.8

Jim Rickards wrote:
Lets do some calculations.
Find a good depth of field (DOF) calculator (google knows where)

Input the values -
-f stop,
-lens focal length and camera (so the crop factor can be figured out.)
-distance to subject.

The calculator will tell you:
-the total DOF
-the DOF in front of the focus point
-the DOF behind the focus point
Then you can look at your model and consider stuff like:
-how far is it from her eye (usual focus point) to
--her other eye
--her ear
--the hair behind her far eye.

After calculating all of the above you may decide:

- to choose a pose where both eyes are the same distance from the camera or almost the same to keep them sharp.

- to choose to keep the necklace blurred or sharp.

There lots to decide. A look at the calculator will be a good start.

Wow! I never even knew such a thing existed. I will check it out. I am sure that it will at least give me an idea of what kind of range I am talking about.

thanks!

Nov 06, 2009 at 12:40 AM

Ian Bower
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p.1 #6 · F 1.8

kakomu wrote:
Ian Bower wrote:Is it just such a narrow DOF that I couldn't possibly get her whole face into focus? should I shoot at a higher F stop for a Head and shoulder shot?
This is probably the biggest issue. At f/1.8, the DoF is very narrow requiring you to shoot straight on to get the whole face in focus. If the person is tilting their head, you'll see the effects of a narrow DoF very easily.

thanks! I guess I will try experimenting at higher F stops.

Nov 06, 2009 at 12:40 AM

ripkoken
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p.1 #7 · F 1.8

A simple rule of thumb is your depth of field will be 1/3 in front of your focus point and 2/3 behind it. The distance will increase with smaller apetures, but the ratio of 1/3 in front and 2/3 behind should remain the same.

Nov 06, 2009 at 12:52 AM

spada
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p.1 #8 · F 1.8

I think that the problem lies more in the fact that it was shot at 1/60th, and not the f/2.5 aperture.
I will let Steady say what he has to say though, because I may be wrong, and look like a fewl.

Nov 06, 2009 at 01:27 AM

jfinite
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p.1 #9 · F 1.8

Canon 50/1.8? I don't think that lens has a good reputation for sharpness.

Nov 06, 2009 at 01:33 AM

Steady Hand
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p.1 #10 · F 1.8

spada wrote:
I think that the problem lies more in the fact that it was shot at 1/60th, and not the f/2.5 aperture.
I will let Steady say what he has to say though, because I may be wrong, and look like a fewl.

Not to worry. I have been known to say something fewlish myself.

The slow shutter speed could certainly be part of the "soft" look. Hand shake....

Nov 06, 2009 at 01:43 AM

Steady Hand
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p.1 #11 · F 1.8

jfinite wrote:
Canon 50/1.8? I don't think that lens has a good reputation for sharpness.

Au contraire, mon ami!

That model /lens is known for being sharp....at the right APERTURE and use.

Of course there may be variations....but it is known as a sharp lens for less than $100.

Highly recommended for a start or a pocket.

Nov 06, 2009 at 01:45 AM

Jeremy1981
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p.1 #12 · F 1.8

One more thought that may add something here: Where was the focal point? When you focused and re-composed, where did you focus? Her hair looks slightly more in focus to me than her face. Also, if you did in fact use her face to focus, there is a chance your copy of that lens might be slightly front-focusing. Some testing with charts and focus points could help with that. (And tripod) Less likely, perhaps, than user error, but another thought.

Jeremy

Nov 06, 2009 at 02:33 AM

Ian Bower
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p.1 #13 · F 1.8

jfinite wrote:
Canon 50/1.8? I don't think that lens has a good reputation for sharpness.

Nikon

Nov 06, 2009 at 04:02 AM

Mark Zwiesler
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p.1 #14 · F 1.8

Jeremy1981 wrote:
One more thought that may add something here: Where was the focal point? When you focused and re-composed, where did you focus? Her hair looks slightly more in focus to me than her face. Also, if you did in fact use her face to focus, there is a chance your copy of that lens might be slightly front-focusing. Some testing with charts and focus points could help with that. (And tripod) Less likely, perhaps, than user error, but another thought.

Jeremy

Jeremy's comments pretty much some up my thoughts as well.

The more information you can provide, the better. We need to know things like, were you using center focus point only, or multiple focus points? One shot focus, or something else? If you were using center focus point then you must have focused and recomposed...but we can only guess how you shot the picture.

There are some pretty simple ways you can test your camera/lens for front or back focus, but first more information would be helpful.

Mark

Nov 06, 2009 at 04:02 AM

Ian Bower
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p.1 #15 · F 1.8

Nov 06, 2009 at 04:03 AM

jfinite
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p.1 #16 · F 1.8

Ian Bower wrote:
jfinite wrote:
Canon 50/1.8? I don't think that lens has a good reputation for sharpness.

Nikon

Hmm, you might want to take a look at Olympus and the 50/f2.

Nov 06, 2009 at 04:40 AM

jdben622
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p.1 #17 · F 1.8

^ comparing a $500 macro lens to a $100 plastic-o?

The 50/1.8 is supposed to be sharp wide open. Her left eye is much more in focus. You probably have a little camera shake issue, but more DOF issue. Unless this was heavily cropped, you're pretty close so your DOF is going to be very thin.

Nov 06, 2009 at 04:52 AM

ratface
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p.1 #18 · F 1.8

I've come to the conclusion shooting with the 50/1.8 wide open that

1) the calculators don't lie about how shallow the depth of field is :-)
2) the picture doesn't lie about how shaky my hand is
3) I inevitably underestimate my ability to move the camera sometime between focusing and shooting, thus potentially exacerbating 1) above

On the odd occasion that I nail a shot with that lens wide open (or close to), I'm always happy; I liken shooting with that lens to the way I play golf...

Nov 06, 2009 at 05:17 AM

capguy
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p.1 #19 · F 1.8

I'd say the focus is pretty good and the picture should sharpen up quite nicely.

If you are shooting with Nikon Dxx your crop ratio is 1.5. The rule of thumb says your maximum shutter speed should be 1/75 s [calculated from 1/(50*1.5)s].

The image is a little over-exposed. With faster shutter speed you would have nailed the lighting and produced a sharp shot.

Nov 06, 2009 at 07:57 AM

Nick Baker
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p.1 #20 · F 1.8

2 issues:

1. The 50 1.8 is NOT super sharp at 2.5. Stop down to about 3.5 for better sharpness. A 2 pass sharpening will help this. (A: high radius, low amount for better midtone contrast...the 1.8 at 2.5 has some halation that destroys midtone contrast (which helps with the appearance of sharpness and "pop". B: regular sharpening)

2. at 2.5 the DOF is too thin to get both eyes in focus from the side a this distance. 3.5 would fix it I bet.

3. (yes i know i said 2 issues) possibly a bit front focused.

Experiment!!!

Nov 06, 2009 at 08:17 AM

wilco54
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p.1 #21 · F 1.8

Well, I like the picture. It probably should have been spot focussed on the near eye and a slightly stopped down aperture (f3-4 or so) would have brought the model's right eye more into focus and still kept nice background blur. I also like the softness but it may be more due to shake! I would try using Manual more and try different combinations - its fun with a patient victim. DSorry, should have said, with f1.8 or f2 teh focus has to be spot on. I have the Canon nifty fifty and its great fun but very sharp - so you will be very sharp in the wrong place if not spot on!

I play golf and photograph the same way, which means the intended focal point is the right or left ear!

Nov 06, 2009 at 08:20 AM

kakomu
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p.1 #22 · F 1.8

Another thing to note: Proximity to the subject will affect the DoF as well. The closer you are to the subject (and closer to minimum focus distance you are) the thinner the DoF. Conversely, the closer you are to hyperfocal focus (infinity) the wider the DoF is. The best illustration I can give is macro photography. The DoF is incredibly thin (on the order of millimeters, sometimes) even with a relatively closed aperture. This has its upsides and downsides. The obvious downside is that focus is more difficult when up close and at a wide aperture, sometimes necessitating a few steps backward. On the plus side, you can always stop down for tight crops to F/2.8 or even f/4 to increase the DoF which helps focus and still maintain a fair amount of background blur and bokeh.

Edited on Nov 06, 2009 at 04:32 PM · View previous versions

Nov 06, 2009 at 02:33 PM

Pfiltz
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p.1 #23 · F 1.8

DOF is the enemy... Not the lens.. per sey...

Simple to understand, and under 10K words.

Shoot the same image, at the far end. Same pose, same lens. Compare..

Nov 06, 2009 at 03:19 PM

Ian Bower
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p.1 #24 · F 1.8

Wow! I've never gotten so many responses to a picture before

I should just rip them out of camera and throw them on here more often !!! ^^;;;

Seriously though, thank you all for your answers. I am going to make my wife pose for a few experiments here in about an hour - will post those results. I am going to try it again at the same distance with different aperatures.

You think this picture is over exposed? hm. I need to get a light meter. =/

Nov 06, 2009 at 03:44 PM

Jacob D
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p.1 #25 · F 1.8

Ian Bower wrote:
Wow! I've never gotten so many responses to a picture before

... well everyone loves to talk about gear and specs whether they admit it or not

I used to own the 50/1.8. I found it to be a sharp lens wide open; not as sharp as say 35L or 135L... but certainly not soft. As mentioned, when shooting at 1.8 the dof is thin, so you have to adjust accordingly. Longer lenses (85, 135 for example) are actually a little easier to use wide open since you are further away from the subject most of the time.

BTW, I found the AF on the fantastic plastic unreliable and sold it for the 50/1.4 - which I didn't find much better. Eventually I sold that one and ended up with the 35L.

Nov 06, 2009 at 04:27 PM


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