shallow DOF and getting proper focus

Elaine · December 8, 2006

All right...what is the point of having a lens that opens to 2.8 and 1.7 if you can't get a clear shot? I've heard that lenses tend to be soft at the extreme ends, but I just did a series of test shots (very rudimentary, but a place to start anyway) and my little 50mm prime doesn't want to give me clearly focussed pictures 'till at least f/4, better at 5.6. Why should I invest in fast glass if I can't use anything below 4 anyway? I would love to use the wider aperture for light and DOF, but AHHHH! I am frustrated and ready to give up! It can't be this hard or no one would take pictures! I especially want to capture kids and get their eyes nice and clear and sharp, not their nose or their shirt or the whole thing a blur. What am I doing wrong and how can I really test to decipher where the issues are? I have tons to learn, but I'm not a complete noob! I've taken some photography classes and have taken a ton of pictures in the last few years. Please help! Thanks in advance!

Elaine

Shay Stephens · December 9, 2006

The 50mm at wide apertures can be finicky when it comes to focus. I find that patience and really concentrating on the focus when shooting in low light pays off, but it can still be a little hit and miss when it comes to focus. But it can be improved with practice.

Pay attention to the areas of contrast where you are trying to focus. If there is not much contrast at the point of focus, but there is just off to the side of it, the camera may grab that area to focus on. Or it not achieve focus at all if there is not enough contrast. Especially important as the light levels diminish.

You may need to add some suplemental light to aid in focusing. I bring a small flashlight with me just in case. I am also about to receive a spilt focus screen that may help me manually focus in low light when the autofocus is not working, even with an f/1.4 lens.

SloYerRoll · December 9, 2006

You definately want to listen to Shay's advise..

You may also want to do some research on which type of focus your camera is using.
Spot, Matrix, Zone, Single or Dynamic Area. All these are different types of focus settings that your camera may have.
Time to get a Chai and sit down w/ the ol owners manual...
Once you have a grasp of what each type of focus does and what it's strong points are. You be quickly on the road to sharp shots!

Nikolai · December 10, 2006

Uhm, Shay...

Shay Stephens wrote:

...I am also about to receive a spilt focus screen ...

Can you elaborate on the details on getting and installing it? I used to use it and love it in my film days, but I wonder how would it work with camera's AF, if at all...

Would it be like an IR mod - a permanent fix that you can't take off w/o much of a hassle?

What body are you getting it for?

TIA!

gus · December 10, 2006

Elaine can you post some shots along with the exif info so we can see what your getting ?

My little 50mm f1.8 is razor sharp & always spot on with focus in light that i sometimes am very surprised with.

GREAPER · December 10, 2006

I also have no problems with my 50 f/1.4. If our subject is very close to you 1.4 is going to have a VERY shallow DOF. If you are focusing and recomposing, it is likely that you are moving enough to lose focus entirely. Even if you are not trying to recompose, the slightest movement foward or backward of your subject could cause you to lose focus.

Most lenses are sharpest in the middle of their range, say f/8. It will not be as sharp at f/1.4.

Remember, your lens focuses wide open, then stops down to the aperature you want, so even at f/8 , the lens is focusing at f/1.4. This is a big advantage of fast lenses.

I hope that helps

SloYerRoll · December 10, 2006

Gotta love those 50 1.8's. Killer prices for fast glass!

Don't bother reading this if you shoot in auto.
Another possibility is you have an incorrect zone selected for your focus.
Below is a visual example (Nikon manual) of what I am talking about.
When I first got my SLR I accidently did this and had to read up on it. Then my beautiful wife was learning the camera and she would hand it back to me and all the shots I would take would be OOF since she changed the zone on me. This is my fault for not being in the good habit if checking my settings yet before I shoot.
Hope some of this stuff is helping..

Copy permission given from Nikon to reproduce this shot.

SloYerRoll · December 10, 2006

Nikolai wrote:

Can you elaborate on the details on getting and installing it?

Hey Nik,
Here is a link to the site for the optics and the info you need:
http://www.katzeyeoptics.com/

If you do a general dgrin search for "split" you'll come up w/ some threads that have info on this as well.

The only down side I see at all is possible light meter anomalies. Which is no big deal if your shooting raw. Unless the readings fluctuate a bunch and you have 500+ shots to send through post and they all need a different tweak.... That's making me nauseous. I'm gonna go lay down..

colourbox · December 10, 2006

If you tend to focus with the center point and then finish the composition, you could be running into a problem that happens with narrow DOF. SloYerRoll's good info touched on this, and you can read more on proper technique in these two links, if this is happening to you:
Don't Recompose!
Why Focus Recompose Sucks

Shay Stephens · December 10, 2006

Nikolai wrote:

Can you elaborate on the details on getting and installing it? I used to use it and love it in my film days, but I wonder how would it work with camera's AF, if at all... Would it be like an IR mod - a permanent fix that you can't take off w/o much of a hassle? What body are you getting it for?

TIA!

I have not received it yet, but when I do I will make a full report. I ordered it for the 20D. And it is just a focus screen you can pop in and out with ease. Nothing permanent here. This is the thread I found it in:
http://www.digitalgrin.com/showthread.php?t=48497

Nikolai · December 10, 2006

Shay,

Shay Stephens wrote:

I have not received it yet, but when I do I will make a full report. I ordered it for the 20D. And it is just a focus screen you can pop in and out with ease. Nothing permanent here. This is the thread I found it in:
http://www.digitalgrin.com/showthread.php?t=48497

Thanks a lot, somehow I missed it... Where did you order it and at what price? Can it also include the etched grid lines?

pug8 · December 10, 2006

If I'm in a situation where the AF iss having hissy-fits, I just switch to manual focus. It gives me more control.

Shay Stephens · December 10, 2006

Nikolai wrote:

Thanks a lot, somehow I missed it... Where did you order it and at what price? Can it also include the etched grid lines?

I ordered it from the website. I got the spilt focus screen with 8x10 marks, I didn't want grid lines. I don't remember the total prices, but it is listed on the website

Nikolai · December 10, 2006

Shay,

Shay Stephens wrote:

I ordered it from the website. I got the spilt focus screen with 8x10 marks, I didn't want grid lines. I don't remember the total prices, but it is listed on the website

I noticed it after I asked the question... sorry...
Last question, I hope: did you a order a Plus ("extra bright") version or a normal one?

Shay Stephens · December 10, 2006

Nikolai wrote:

I noticed it after I asked the question... sorry...
Last question, I hope: did you a order a Plus ("extra bright") version or a normal one?

I ordered the normal one. I just got an email saying the screen is done, and will be shipped out Monday :-)

Nikolai · December 10, 2006

Shay,

Shay Stephens wrote:

I ordered the normal one. I just got an email saying the screen is done, and will be shipped out Monday :-)

Cool, congrats, can't wait for your review:-)

Elaine · December 11, 2006

Thanks for all the feedback and information! I'm curious to hear how the split screen works out, too.

I got out my manual to refresh my memory on how my focus system works. I was reminded that if I hold down my selected area of focus on my controller keys, it will stay locked there until I let it go (I have been using the half-press on the shutter to regain focus at the same spot when I don't have to). So, it was good to revisit the manual.

If by shooting in Auto you mean the "green" mode (SloYerRoll), I never do that. Normally, my camera is set for aperture priority, but I've been forcing myself to use manual lately. I've been using the focus selection mode for a very long time, where I pick my point of focus with my controller keys, half-press the shutter to get focus on that spot and then click, so I do not have to recompose the image. I am sure that when a very shallow DOF is in play, I'm probably being frustrated by some movement from my subject and/or myself and causing my plane of focus to alter ever so slightly. How does one take shallow DOF pictures of kids anyway??

I've tried using manual focus and it doesn't seem to help. What I see nice and sharp in my lens is not always what I see on the screen later.

I will try and post some shots later. That would probably be most helpful.

Thanks for the help and encouragement!

Elaine

Carbon Based · December 11, 2006

Elaine

Here http://www.dofmaster.com/dofjs.html DOF calculator site, use your camera and punch in some numbers and you'll see wide open DOF is some times limited. And if your subject is figgity kids

. Also beaware that Auto focus uses contrast to focus on. So if for instance the contrasty part is the side of the subjects head against a dark background then the distance from the middle of your ear to the tip of your nose could be a couple of inches and be slightly OOF.

Elaine · December 11, 2006

Carbon Based wrote:

Elaine

Here http://www.dofmaster.com/dofjs.html DOF calculator site, use your camera and punch in some numbers and you'll see wide open DOF is some times limited. And if your subject is figgity kids . Also beaware that Auto focus uses contrast to focus on. So if for instance the contrasty part is the side of the subjects head against a dark background then the distance from the middle of your ear to the tip of your nose could be a couple of inches and be slightly OOF.

Hey, thanks! That was a fun site...wow, the DOF does not leave much room for error on some of those settings. I guess I need more patience!

Here's one example shot...I focused on the mom's eyes (did not recompose), but to me, the baby's hands holding the jingle bell look the most sharp in the image...

Carbon Based · December 11, 2006

It could be that the white cuffs against the red sleaves is what you AF used to focus on. There is a thing called back focus, I don't completely understand it but you may want to do some research. Sorry I couldn't be more help.

Some manufactures software (ZoomBrowzer by Canon) will show you which focusing points were used in an image. Not sure what camera or software you use but you may want to explore that route too.

Elaine · December 11, 2006

Carbon Based wrote:

It could be that the white cuffs against the red sleaves is what you AF used to focus on. There is a thing called back focus, I don't completely understand it but you may want to do some research. Sorry I couldn't be more help.

Some manufactures software (ZoomBrowzer by Canon) will show you which focusing points were used in an image. Not sure what camera or software you use but you may want to explore that route too.

I use a Konica Minolta 5D with Photoshop Elements 3.0. I could check and see if the software that came with the camera would show me my focus points. I recently had my camera in for service for front focus (at least that's what I thought was happening). I did some tripod tests a few months ago...set up three cake mix boxes on a table, one in front of the other but offset so you could see all three. Then I focused on each one to see what happened. When I focused on the middle one, the front one was more sharp. When I focused on the back one, the middle one was more sharp. Focusing on the front one produced an image that just wasn't quite clear anywhere...close but not quite. I've had my camera back now for a few weeks, and I was hoping to just be able to throw on my f/1.7 and take miraculous shots, but I guess it doesn't work that way!

As I mentioned before, I never noticed this issue with my kit lens, only when I got new glass did this show up.
I'm taking more kids' Christmas card pictures today! I hope all goes well. Thankfully, I think I'm more picky and know more about photography than all my friends I'm taking photos for!

Elaine

PS - I'm soaked in the PNW too!

Nikolai · December 11, 2006

More on split prism
I was almost ready to order me one a s Christmas gift, when I became aware of another fact: split prism messes up central spot metering (which is not present on 10D and 20D, but is a nice feature of 30D), and may affect central metering in other modes, too (unless you're meter the whole screen, where the effect is negligible).

That is, unless you're using f/2.8 or faster glass - or always meter by a non-central point.
Since the majority of the glass I currently own is not that fast, I guess I'd have to postpone..

:cry

THust thought I'd share...

Aso: they have a bulk discount, so if a few peoeple decided to get them together, it's possible to save some $$$...

Carbon Based · December 11, 2006

Elaine wrote:

Elaine

PS - I'm soaked in the PNW too!

Really where abouts? I'm just west of Portland. Yesterday my daughter and I went to see the Ansel Adams show at the World Forestry Center. All I can saw is WOW he was the master!

To see those images in person makes all of the poster/cards ect of his work pale by comparison.

Elaine · December 11, 2006

Carbon Based wrote:

Really where abouts? I'm just west of Portland. Yesterday my daughter and I went to see the Ansel Adams show at the World Forestry Center. All I can saw is WOW he was the master! To see those images in person makes all of the poster/cards ect of his work pale by comparison.

Oh, how neat! I had not heard about that exhibit.

We're in Hillsboro.

LiquidAir · December 11, 2006

Getting sharp images at wide apetures is difficult. On my camera, only the center focus point is accurate enough for f/2 and wider lenses, so I force it to always use the center focus point. In addition, at f/2, focus and recompose can cause focus errors if your subject is closer than about 6 feet. The net result is I have to resort to a variety of trickery if I want my focus point to be anywhere other than the center of the frame. Luckily Canon makes an alternate focus screen for my camera that makes manual focus easier (no split screen, just more sensitve microlenses). Also, with focus confirmation in manual focus and some jockeying of the focus ring, you can get some useful information out of the outer focus points despite their lower accuracy. I have invested many, many hours of practice in to accurate focus and I still miss fairly often.

Carbon Based · December 11, 2006

Elaine wrote:

Oh, how neat! I had not heard about that exhibit.

We're in Hillsboro.

No kidding me too!

You just have to check out the exhibit.

mikeb380 · January 14, 2007

Elaine wrote:

All right...what is the point of having a lens that opens to 2.8 and 1.7 if you can't get a clear shot? I've heard that lenses tend to be soft at the extreme ends, but I just did a series of test shots (very rudimentary, but a place to start anyway) and my little 50mm prime doesn't want to give me clearly focussed pictures 'till at least f/4, better at 5.6. Why should I invest in fast glass if I can't use anything below 4 anyway? I would love to use the wider aperture for light and DOF, but AHHHH! I am frustrated and ready to give up! It can't be this hard or no one would take pictures! I especially want to capture kids and get their eyes nice and clear and sharp, not their nose or their shirt or the whole thing a blur. What am I doing wrong and how can I really test to decipher where the issues are? I have tons to learn, but I'm not a complete noob! I've taken some photography classes and have taken a ton of pictures in the last few years. Please help! Thanks in advance!

Elaine

Elaine;
A few things you need to change for the type photos you are taking. First to answer your question about why a fast lens.... Any lens has more distortion wide open, use a fast lens (1.2/1.4) so your smaller stops, ie. 2.0,2.8, etc. have less distortion. secondly, the closer you are to your subject the shallower your DOF. The 50mm lens is wrong for the type of photography you are shooting. You need to use at least a 70-75-80mm lens. I prefer a 100mm although I'm using an 80mm as my standard lens on my Digital Rebel at present. With your subject at the same size in the frame your DOF will be larger for the longer distance. With the lens you are using, 50mm, you have no room for error in focusing. You need to use manual focus as even a little creep in AF can throw your focus point totally out of focus. One other thing you can do is get a Kodak Master Photoguide, they are small enough to carry in a large pocket and certainly small enough to carry in a camera bag. The Guide has DOF calculators, really a circular slide rule, which you can use in the field. I got mine used on Ebay but I think amazon might have them. You want the pocket model although the full size is good if you can carry it with you.The other thing you can do is use manual focus lenses on the camera. Those usually had DOF calculators on the lenses and since you need to use MF anyway, they would be just the thing. Not to mention you can get an outstanding Pentax, Canon, or Nikon lens for lots less than you pay for your manufacturer lenses. A 1.2 Canon FD SSC lens can be had for about $25.00-$50.00 and will be sharp as a tack at f1.8 and above. I can follow focus mine even for hawks on the fly, so you should certainly have no trouble with moving kids. Even less for kids who are sitting still. You just have to practise to get used to it. Right now I am using a Russian 2.8/85mm lens for my primary lens on my Canon F1, a great combination. The biggest thing is that where you focus is where your focus will stay, unless you change aperture. Changing aperture can also change point of focus on your lens, so if you focus at 1.2 and then change to 2.8 for the photo your focus can be way off. at larger apertures I focus with the lens stopped down, when using smaller apertures the lens isn't as fussy about changing f stops. In my photo classes I make all the students use manual focus and exposure, no automatic and you can see the improvement in their photography in a couple of weeks on manual.

Also you say you want to use the faster lens for light and DOF but they are mutually exclusive. The smaller the f stop the longer the DOF and vice versa. What you want is a matter of cake and eat it too. If you are shooting inside get a soft light box with an incandescent light which will give a well modeled look to the photo and more room for smaller openings and better DOF. You don't need powerful lights for this, just enough to boost your aperture a couple of stops. Reducing shutter speed on stationary subjects can also yield more light for you to use for aperture settings/DOF.

As to it being hard, I and thousands of others, learned and grew up with no light meters, no range finders, no interchangable lenses, no auto anything, and we learned how to use the camera instead of letting that dumb computer inside do it for you. My Camera as a boy learning was a 2¼X2¼ Speed Graphic Which I think weighed about 100 lbs by the time the day was over. I used it for child photography, sports, landscape, and whatever else. I even carried it to the top of the Washington monument (walking up 365 steps and then back down). You can do what you make up your mind to do. Be positive.

Hope this helps you get the pictures you want.
Good Light
Michael

shallow DOF and getting proper focus

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