Manual Focus (Portraits)

[Kayaker72]

I was also disappointed with my50 mm f1.8, an impulse buy about a week ago, until last night. I have a 7D and after reading this thread I decided to play with the microadjustments. Turns out it was front focusing by 4 to 6 inches (at 4 ft). I haveset the microadjustments to +20 and I think it is stillfront focusing just a little, but my subject is now in focus (just toward the rear of the DOF).With the "microadjustment" the 100% crops look pretty good and the overall picture is looking really sharp. I can see why people like this lens so much.


I am not sure this helps you, other than to confirm that there may be a front focusing issue with the 50 mm f1.8. As others have said, maybe it is at least worth a call to the repair shop to see how much it might cost to fix.

[scalesusa]

You need to determine if its the camera, lens, or perhaps both that are out of tolerance.


Be sure to place your camera on a tripod to test the autofocus, and compare another lens with the 50. If the other lens is sharp at f2 or wider and the 50 is not, get the 50 fixed or replace it. If both are mis-focused, the camera is suspect.


I don't believe this is your problem, but, another thing to consider is that if you handhold the camera and use 1 shot AF, it is common to lean forward or away after focus is achieved, and this will affect focus.

[loveglory]

Wao, Its damn closeup with sharp quality.

[MattG]

The 50 1.8 is probably the cheapest lens you can buy these days. Are these fairly new purchases or are they a few years old. I wonder if the focusing machanisms are just worn and are no longer in sync? The review of the lens on this site was not to favourable but it does state:


The Canon EF 50mm f/1.8 II Lens' strongest quality is its sharpness. Sharpness performance wide open (f/1.8) is decent, but the Canon 50 f/1.8 is very sharp at f/2.8 and beyond. It is slightly sharper than even then Canon EF 24-70mm f/2.8 L USM Lens.


You would think you should be getting decent shots. Just not sure why you would use a lens of that quality on a 7D or 5D [:P]


MattG

[Kayaker72]

My 50 f/1.8was an impulse buy about 2 weeks ago, so very new. I am still glad I bought this lens as it has allowed me to play with a prime and lower apertures, but the conclusion I've come to is that it is sharp, but does seem to have a focusing problem. I spent ~200 pictures playing with the focus and trying to use the micro-adjustment feature to correct it. Obviously, I am still learning and this was the first lens I've tried to microadjust, but I would found I could dial it in at one distance, but then I would set up on another distance and it was again have slight focusing issues. I also noticed that focus was much sharper using a single point rather than multiple points (probably to be expected, but there seemed to be a significant difference). Finally I was doing a test looking at a printed page at ~20 degree angle from ~2 ft away. The lens could focus in front of my target or behind my target, but never on my target. I am currently thinking that the gears that drive the autofocus are so course/large that they are cause autofocus issues. This problem is somewhat random when using a single point focus (depends upon where you are in relation to the gears), but comes more into play when the camera tries to bring multiple points to within focus as you end up with a general "softness."


Does this sound plausible?

[Daniel Browning]

The lens could focus in front of my target or behind my target, but never on my target.

I sold my 50mm f/1.8 before I got a body with AF microadjust, so I don't know if I would have had the same experience as you or not. However, one thing I would mention is this: only the center point autofocus has the f/2.8 accuracy, and even then it's only rated to 1/3 DOF. So if you haven't already, try seeing if it's consistant at f/3.5 or so (let autofocus run wide open at f/1.8). If it works that way, then you're probably getting normal results (the limitation of the autofocus system). If it's still inconsistent, then the problem is elsewhere.

[Matt.s.Maneri]

I have an XSI, and usually use the 50mm f/1.8 mkii lens for portraits. One thing that's been bothering me lately is that I always have to use manual focus when doing portraits, which really turns out to be hit and miss. Autofocus just never gives me sharp photos. Is it because of the lens that I have to use manual focus? I know that using an aperture like 1.8 is going to give me a shallow DOF and therefore make it harder to focus on a precise area, but I have to manual focus even when the aperture is set to f/5.6 to get a sharp photo. Is this normal?

[url="http://www.flickr.com/photos/48939759@N07/4907065533/]http://www.flickr.com/photos/48939759@N07/4907065533/[/url]


Above is a link to a picture I particularly like; it was just a fluke that I focused well.
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I also use my 50mm for portrait shots, although mine is not the 1.8 I still think my method might be a decent alternative to shipping it in.


I realize this still comes down to manual focusing but really if it is for a portrait its not of great importance to have the AF anyways. I would set your camera on a tripod and manual focus on a person trying to make the eyes are sharp as possible through your own view finder, after review your image and see if its actually sharp if not find the proper sharpness through a process of adjustment. Once you have accomplished a sharp image adjust your diopter to make that sharp through your view finder. I know this sounds rather tedious to do for each lens but once you get the hang of it you can do it rather quickly. Most of my lenses focus fine and I still find my self doing this to insure my manual focus comes out sharp.


I simple like the know what I see through my view finder is what I get.

[neuroanatomist]

...make the eyes are sharp as possible through your own view finder...Once you have accomplished a sharp image adjust your diopter to make that sharp through your view finder.


I simple like the know what I see through my view finder is what I get.

Ahhh, but the problem is what you see is not what you get, unless you have installed a different and more appropriate focusing screen in your camera (assuming your body has that capability; my 7D with it's transmissive LCD in the VF does not, and the Rebels do not either).


The reason that<span>what you see is not what you get is because the standard focusing screens have laser micro-etching designed to produce a brighter VF image, primarily to compensate for the reduced light transmission from variable-aperture consumer zoom lenses. So, what you see in the VF with the standard focusing screen is actually somewhere around f/2.2 even with a faster lens. That means even with a wide aperture for your desired OOF blur, you are basing your critical focus through the VF looking at a deeper DoF than that to which your exposure is set.


<span>You can check this for yourself - take your fast prime, hold the DoF preview button on the side of the lens mount as you close the aperture down from wide open. You won't notice the VF getting any dimmer until you hit about f/2.2.


<span>As a side note on my 7D, even though the VF doesn't get any brighter as you go wider than f/2.2 (due to the etching to brighten up typical slow lenses), the AF points in the 7D's transmissive VF get progressively more 'washed out' by the additional light - the light is getting in there, but the focusing screen prevents it from reaching your eye.


That's the reason that, if you want to do a lot of manual focusing, you really should install a focusing screen designed for it.

[Matt.s.Maneri]

If you were to set your diopter accurately what you focus on will still remain sharp. Though yes If your using one of the lower end camera body's the DOF preview is supposed to loose its accuracy around f/4 where as the 1d's and 5d go to 2.8 .

[neuroanatomist]

If you were to set your diopter accurately what you focus on will still remain sharp.

Hey Matt,


I guess my point is, it will look sharp. But, it may not be sharp in the final image. Say you use the diopter to correct for any front/back focusing issues with a particular lens. If you're using the focusing screen that came with your camera (whatever model), that focusing screen is showing you the DoF of f/2.2, not what you've chosen as an aperture for the shot. For example, with a 50mm f/1.2L lens on FF at a subject distance of 10 feet, the DoF at f/2.2 is about 20". So, you focus on the eyes of your subject - any focal plane within 10" on either side of the eyes will appear sharp in your diopter-corrected viewfinder. Regardless of how you set the diopter, your VF is only capable of showing you f/2.2 depth of field. For a particular shot, you happen to turn the MF ring so you're actual focal plane is 8" from the eyes - with your standard focusing screen, the eyes appear perfectly sharp in your VF. You could turn that MF ring a little in either direction and your focal point would still appear perfectly sharp. Now you take the shot at f/1.2. The DoF at f/1.2 is a little more than half of what you see in the VF - just 10.3", meaning ~5" on either side of your subject's eyes. Since you actually focused 8" from them (it looked sharp, even zoomed in on the LCD after a test shot), your subject's eyes are now 3" out of the DoF, and losing sharpness due to OOF blur (in addition to the softness resulting from shooting a 50m f/1.2L wide open).


Having said that, how you manually focus makes a big difference - focusing back and forth and settling in the middle of where the image drifts OOF on either side, you are focusing on the middle of the DoF, however wide it actually is - in that case, you should be getting accurate focus even with the artificial f/2.2 DoF you're getting with the standard focusing screen.

Though yes If your using one of the lower end camera body's the DOF preview is supposed to loose its accuracy around f/4 where as the 1d's and 5d go to 2.8 .

Nothing to do with the body or the DoF preview function on that body, rather it's determined by the focusing screen. The standard focusing screen (even in 1-series bodies AFAIK, definitely in the 5DII) is f/2.2. Period. You only see the real DoF with the DoF preview (or whenever looking through the VF with with a lens that has a maximum aperture wider than f/2.2) if you install an optional focus screen, or if you use Live View and look at the LCD. For your 5DII, you'd need the EG-S screen, which according to Canon, "...improves the ease of focusing when doing manual focus, but is not recommended for use with lenses slower than f/2.8. With these slower lenses, the viewfinder will actually look darker than with the standard Eg-A screen." That's their backhanded way of saying the standard Eg-A screen that came with your 5DII is not capable of showing your the true DoF of a lens faster than f/2.8.


--John