Am I doing something wrong?

[Manofmayo]

Last night I had the opportunity to do some nude artsy glamour shots in a studio environment.I normally don't take pictures of people because the pictures never turn out like I had envisioned them to. Most of my shots are landscapes and I have has an SLR type camera since 1981.


So here is the setup: White backdrop in a 15'x15' modeling area, (2) Profoto Strobes set at approx. 3/4 w/ softboxes (3x6?). ISO 100, speeds-1/125 to 1/160, f/10 to 8, Canon xti w/ 70-200 L f4 (non-IS). Sandisk 4gb Ultra 2 memory cards. I was 8-10' from the model. I shoot RAW.


First the technical complaints:

• Shutter Lag-trying to catch a swooshy hair shot was difficult at best, as most shots were at the tail end of the hair shot (usually out of picture).
• Tight head shots were not tight at all.Now I need to crop the shot to get the best picture. What I saw in the viewfinder was not what I saw on the screen. Never was much of a problem w/ landscape shots, now I notice it more than ever before.
• I didn't notice slow transfer speeds on the first memory card, but the second was horrible, I missed many shots. Is there that much difference between identical cards (I bought both at the same time this year).
• d

Next the technique issues:

• I thought that the depth of field I was using would allow me to focus (example here) on the chest and still get a clear & sharp image of the face. Instead of the face isn't as sharp as I would expect. My DOFMaster app on my iphone shows I have a DOF of 1.18'. Am I expecting too much from the equipment?
• What do I focus on? The center AF point is the only one set (and is always set that way). I was hoping to have a sharp face and body if I shot the body. I was set to AI Focus the whole time.

I will probably do something similar in 2-3 weeks. I want to have a higher keeper rate this time from improved technique. I don't think its a good idea to post the pictures given they are nudes, however, I am willing to send one or two out if I feel comfortable with your older posts (just don't want someone to use them for their own gain or post them to a porn site).


I have contemplated buying a 50D, preferably used, however I have purchased 4 lenses this year and can't just the purchase now unless I sell the xti, which I would rather not do so I can keep it as a backup.


Thanks

[crystalshadow]

A few (possible answers).


Shutter Lag: I noticed this a lot on my XTi (I shoot a lot of sports). I'd have to anticipate the shot and get on the shutter just before it happened. I have since upgraded to a 40d a love the speed increase.


Slow transfer speed: I've had similar problems between old and new memory cards on the lower end (two of them were ultra II). Lately I haven't noticed, I switched to Sandisk Extreme III and never looked back. Sandisk currently has a great rebate on them too.


DOF: Two things: Does your depth of field calculator take the 1.6 crop sensor into account? Not sure how much of a difference that will make, but it does change the DOF. Alternatively your camera/lens might not be focusing quite accurately. With that 70-200 (which I also have and love) I got more accurate focus if I zoom in all the way first, focus, then zoom out and compose my shot. It's a pain, but I get a higher keeper rate that way. I usually keep it on one shot AF unless I'm shooting a moving subject.


Not much help, but maybe some answers for you.

[Keith B]

I'd focus on the face. Softer focus on the chest will not seam nearly as out of focus as faces will. Unless they are on a very close plain one will never be as focused as the other.

[Sean Setters]

You know, I think we're gonna need to see example shots so we can give you the best ideas on how to do it right next time.





:-)





hehe...sorry, couldn't help myself.

[neuroanatomist]

• Shutter Lag-trying to catch a swooshy hair shot was difficult at best, as most shots were at the tail end of the hair shot (usually out of picture).

<div>You can test shutter lag with the following method, with credit to Fred Shippey:</div>
<div>1. Download this quicktime movie:http://homepage.mac.com/prof_pixel/products/lagtest_a.mov</div>
<div></div>
<div>2.Watch the movie through your camera's viewfinder. It starts with a countdown timer on a black background with beeps and numbers: 5 - 4 - 3 - 2 - 1, each beep/number represents one second. They are designed to help you get set to push the shutter release at -0-. When you see -0-, snap a photo of the screen.</div>
<div>3. Examine the picture you just made. Numbers on a white background are tenths of a second up to 1 second which starts the beige background times ( 1.0 seconds to 1.9 seconds ). 2 seconds to 2.5 seconds are on a blue background. The number you see is the amount of shutter lag your camera has.</div>
<div>For comparison, after several shots my T1i averages 0.15 seconds of lag between focus/exposure lock and shutter release. Also, in a well lit room with an 85 mm f/1.8, with focus set to the closest position, there's about a 0.5-0.6 second lag total for focus lock on a subject at infinity (full traverse of the focus range) from initial press of the button to shutter release.</div>
<div>

</div>

• Tight head shots were not tight at all.Now I need to crop the shot to get the best picture. What I saw in the viewfinder was not what I saw on the screen. Never was much of a problem w/ landscape shots, now I notice it more than ever before.

<div>The XTi (and I think every Canon camera except the 1D series) have a 95% viewfinder coverage, meaning you're only seeing 95% of the full FOV through the viewfinder (the LCD shows 100%, but that only helps in the newer models with Live View, and in that mode focus is very slow). So, it will help to fill, and I mean fill, the viewfinder frame with your subject - get in tight!</div>
<div>

</div>

• I didn't notice slow transfer speeds on the first memory card, but the second was horrible, I missed many shots. Is there that much difference between identical cards (I bought both at the same time this year)

<div>Shouldn't be. Try doing a low-level format of the card. Also, make sure you didn't change image format in between (from jpg to RAW+jpg, for example).</div>
<div></div>
<div>

</div>

• 
  
  
• I thought that the depth of field I was using would allow me to focus (example here) on the chest and still get a clear &amp; sharp image of the face. Instead of the face isn't as sharp as I would expect. My DOFMaster app on my iphone shows I have a DOF of 1.18'. Am I expecting too much from the equipment?

• What do I focus on? The center AF point is the only one set (and is always set that way). I was hoping to have a sharp face and body if I shot the body. I was set to AI Focus the whole time.

<div>Keep in mind that with an f/4 lens you are not able to use the high-precision focus point (the center AF point is a cross-type sensor, but requires f/2.8 or faster to function that way, else you lose the high-precision benefit). Roughly, the cross-type sensor is accurate to within one-third of the DOF, whereas the standard sensor point (which is what you have using an f/4 lens) is accurate to within the full DOF. So, in your example with a DOF of 1.18', the camera can achieve a focus lock that is actually where you're aiming +/- 0.59'. So, for example, if a particular shot locked 6" behind where the AF point lands on the body, and the head was 9" forward of that point, the head is out of the DOF. You might consider a faster lens to get the benefit of the high-precision AF point. But the simple solution is to focus on the eyes - that's what most viewers will expect to be in focus.</div>
<div></div>
<div>Hope that helps...</div>

[MOF_Sydney]

A couple of suggestions/observations:

• I always set the focus point on the eyes. I find that if the eyes are absolutely focussed the picture has the overall impression of being well focussed.
• Personally I would increase both the shutter speed (to perhaps 1/250th or 1/320th) and the aperture (to perhaps f11). You mentioned "swooshy hair" - this means the model is moving and, her head at least, is moving fairly quickly. You need more than 1/100th to "stop" that motion and get sharp focus on the face. Increasing the aperture a bit will increase the depth of field. (You're shooting against a white backdrop so you're not looking for background bokeh. This may mean you have to increase the ISO a bit, but 200 and up to even 400 in a controlled lighting situation won't be a problem. (I recommend increasing the ISO rather than the lighting because more light will give more complications with regards to shine and reflection on the skin.)
• Shutter lag is just what it is. According to Bryan's review it is 100ms (a tenth of a second) on the XTI. It is lower on the higher end bodies - 59ms on the 50D and 7D and 40ms on the ID. Given the reality of the situation that you have the camera you have, you just need to learn to anticipate. It does become "natural" after a while.

My two cents worth. You may be able to post a few examples - crop to just head and shoulders or face with back turned maybe. Could perhaps be a bit more helpful if I could see the photos.

[Manofmayo]

• Ok, so do I pre-focus (manual focus?) on the eyes and leave it set until the model changed position? But if the model is dancing around, she will be in &amp; out of focus, so what do I do then?
• I am willing to up the ISO to 200, but I feel 400 has been too noisy for me unless there is lots to fill the image. Tho I will try a few shots at 400.
• The diffraction on the XTi is f/9.3. If I am looking for crisp headshots, shouldn't I keep the aperature at f/9 or less?
• A question about AF sensors. If I am shooting w/ a f/2.8 lens at f/8 w/ a DOF of 0.57' at 8 feet, how much better is the focus accuracy? I get that with a slower lens it could be +/- 0.28', is it within a 0.1' or is there some formula I can use? I do have 4 lenses at 2.8 or better, I just can't afford to have a longer lens faster than 4.0.

Thanks for all your comments and suggestions, I will post a few pictures later tonight or tomorrow.


Harold

[neuroanatomist]

You can certainly use AF (and since your model will move and you're working with a narrow DOF, you'll want to use AF). You just need to focus on the eyes (the half-press of the shutter locks the focus), then recompose and shoot.


You can likely use smaller apertures - in general, a little loss of sharpness due to diffraction is well-tolerated for portraits.


The general rule is as stated above; the center AF point is accurate to 1/3 of the DOF when used with an f/2.8 or faster lens; the other AF points, like the center point with a lens slower than f/2.8, are accurate to within the DOF. Note that it does not matter what the aperture is set to for the picture - the aperture is wide open for focusing, then stops down just at you take the shot (which is why there's a DOF preview button!).


RE:"I do have 4 lenses at 2.8 or better, I just can't afford to have a longer lens faster than 4.0." - If you mean zoom lenses, yes - fast zooms are $$$. Have you considered a prime? The 85mm f/1.8 is a great lens for portraits on a 1.6 crop body (136mm equivalent for 35mm, which is a 'classic' focal length for tight head shots, and works for full body shots with nice compression if you have a large space to work in). On a crop body like the XTi, a 50mm lens equates to 85mm full frame (a 'classic' portrait length for body shots) - Canon's 'nifty-fifty' (the 50mm f/1.8) is ~US$100, and is a great value and quite sharp lens (focus is accurate but loud and slowish, and bokeh is poor, but neither of those should matter much in a studio setting).

[Manofmayo]

The general rule is as stated above; the center AF point is accurate to 1/3 of the DOF when used with an f/2.8 or faster lens; the other AF points, like the center point with a lens slower than f/2.8, are accurate to within the DOF. Note that it does not matter what the aperture is set to for the picture - the aperture is wide open for focusing, then stops down just at you take the shot (which is why there's a DOF preview button!).


RE:"I do have 4 lenses at 2.8 or better, I just can't afford to have a longer lens faster than 4.0." - If you mean zoom lenses, yes - fast zooms are $$. Have you considered a prime? The 85mm f/1.8 is a great lens for portraits on a 1.6 crop body (136mm equivalent for 35mm, which is a 'classic' focal length for tight head shots, and works for full body shots with nice compression if you have a large space to work in). On a crop body like the XTi, a 50mm lens equates to 85mm full frame (a 'classic' portrait length for body shots) - Canon's 'nifty-fifty' (the 50mm f/1.8) is ~US$100, and is a great value and quite sharp lens (focus is accurate but loud and slowish, and bokeh is poor, but neither of those should matter much in a studio setting).
<div style="CLEAR: both"]</div>

Ok, tell me if this is right: if I continue to use my 70-200 f4 at 10 feet, which has a total DOF of 0.93' (focused wide open), then the focus will be correct within 0.46' +/-, even if I shoot at f8. However, if I used a 70-200 f2.8, which has a total DOF of 0.65' (focused wide open), then the focus will be correct within 0.22' +/- (total front and back) or is it 0.11' +/- (to the front and another 0.11' +/- to the back).


I looked up circle of confusion for my XTi and its 0.019mm. If I wanted to blow up the picture to beyond thelimits of COC, then will I need a bigger COC? If yes, is that why a full frame sensor is better for blow-ups and not the number of pixels?


I have a few primes...the 50mm 1.8, 100mm 2.8 macro (non-L), and a 135mm 2.8 sf. My other 2.8 lens is the Sigma 18-50 2.8, which takes sharper pictures between 18-24 than at 50mm. I think the space is 15x45, so I have space to move back if needed.


Thanks again.

[MOF_Sydney]

Harold,


Regarding your points/questions of 22 November:

• Manual focus - no. I'd use AI Servo but certainly one of the AF modes. My point was to set the focus point on the eyes rather than the body.
• ISO - there is a tradeoff between using a higer ISO or adding more light. Adding light gives more reflections off the skin and detracts from the natural skin tones (and when the photo is mostly skin the skin tone really matters.
• Diffraction - again there is a tradeoff, this time between DOF and diffraction. Diffraction increases slowly and any serious lens is well capable of using f11 without noticeable degradation. An aperture of f11 gives you more DOF than f8.

You simply need to experiment with all these different combinations of speed, aperture and ISO to get the right balance - as you see it &amp; for the photos / photo effects you want.


It is much easier to do these set up experiments with an inanimate object that doesn't move. I have a large teddy bear that I plonk in a director's chair (hence his nickname "Director Bear." With Director Bear I can simulate almost everything except movement blur and skin reflections (because of course he is fur covered). I can check general lighting and DOF (the individual fur fibres give an easy to see indication of in focus to slightly oof). Because he doesn't move I can change anything and test different arrangements.


Then when you bring the model in you don't spend as much time messing about with setup. The issues then are mostly to do with posing and light reflections.


Cheers,


Michael