need depth in digital photography- Help!

Hi All,
I'm new here and need help...
I tend to be shooting with the Nikon digital cameras these days- although I miss the magic of film- and am running into a depth of field issue. I shoot portraits with a 100mm macro lens,& at head and shoulder framing (about 5' away) I still can't get tip of nose to ears sharp...even at f29.
I remember from my photo school days that 4x5 was sharper, but do you think I could pull 1.5 ft of depth without tilts if I put a Nikon on a 4x5? maybe with a 240mm lens?
Any help is appreciated!
Thanks.

No, a Nikon on a 4x5 will make matters worse. Tilt won't help you, unless you want chin and hair to be totally blurred. Longer focal lengths tend to give less depth of field, a 100mm lens on a 4x5 with a Nikon attached will give you exactly the same depth of field as a 100mm on the Nikon at the same aperture. f29 is far too much for this setup, diffraction will mess up the overall sharpness. Check the MTF figures on page 2 of this review: http://www.photozone.de/nikon--nikko...report?start=1

Michael

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Originally Posted by ewax1

Hi All,
I'm new here and need help...
I tend to be shooting with the Nikon digital cameras these days- although I miss the magic of film- and am running into a depth of field issue. I shoot portraits with a 100mm macro lens,& at head and shoulder framing (about 5' away) I still can't get tip of nose to ears sharp...even at f29.
I remember from my photo school days that 4x5 was sharper, but do you think I could pull 1.5 ft of depth without tilts if I put a Nikon on a 4x5? maybe with a 240mm lens?
Any help is appreciated!
Thanks.

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No.

Wow

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Originally Posted by Michael E

No, a Nikon on a 4x5 will make matters worse. Tilt won't help you, unless you want chin and hair to be totally blurred. Longer focal lengths tend to give less depth of field, a 100mm lens on a 4x5 with a Nikon attached will give you exactly the same depth of field as a 100mm on the Nikon at the same aperture. f29 is far too much for this setup, diffraction will mess up the overall sharpness. Check the MTF figures on page 2 of this review: http://www.photozone.de/nikon--nikko...report?start=1

Michael

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So according to the chart, a Nikon 105mm is sharpest at 5.6 or 8...
How can I get more DOF? would a 90mm rodenstock give it to me? that is if a 90mm is a 90mm same for all formats....Is there a depth of Field difference between a barrel focus lens and a bellows focus lens?
Thanks!

"digital nikon" == ?
and there is no micro nikkor in 100mm focal either

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Originally Posted by ewax1

So according to the chart, a Nikon 105mm is sharpest at 5.6 or 8...
How can I get more DOF? would a 90mm rodenstock give it to me? that is if a 90mm is a 90mm same for all formats....
Thanks!

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Search for DOF calculator on google.

I have done many portraits with both a 135mm f/2 and 300mm f/2.8, both at almost full aperture, and I have no problems with DOF. Something else is awry with your setup.

I agree that something else is awry here. But to some of the questions:

--Everything with the any digital camera will depend on the size of the chip. On a full-frame digital, a 105mm is a 105mm. However, on a Nikon DX, a 105mm is a 136.5. That may be throwing off anything you see from a DOF chart. Canon has the same attributes.

--There are 100mm micro lenses out there that will fit a Nikon, but they're off-brand and I wouldn't recommend them. Nikon does make a sweet 60mm, but could be a 78mm, depending on your camera body.

--When a chart tells you that a lens is really sharpest at on f-stop or another, it doesn't mean you loose focus at the higher f-stops. With most, you have to try really hard to tell the difference to the naked eye.

--I also agree that putting the Nikon on a 4x5 won't help. The large format lenses are made to handle huge image circle compared to the size of the image that would be recorded. And, you probably wouldn't be able to focus very well even though a viewfinder.


Something else is going wrong here.

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Originally Posted by John Flavell

I agree that something else is awry here. But to some of the questions:

--Everything with the any digital camera will depend on the size of the chip. On a full-frame digital, a 105mm is a 105mm. However, on a Nikon DX, a 105mm is a 136.5. That may be throwing off anything you see from a DOF chart.

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105mm would have field of view of 157.5mm on a Nikon DX (1.5 crop factor) (but same DOF assuming shooting from the same position).

Macro lenses are designed to allow for easy fine tuning of focus on very close objects. They don't work well for focusing for portraits. The focus control beyond 1 meter can be very tricky because a slight change of focus can move the focus point significantly.

DOF for a 100mm lens @ 5', f/28, should be something like 10", which should be plenty, unless your sitter has an unusually large head, or a very long nose. f/16 should do it for normal subjects.

As long as the magnification remains constant, the focal length doesn't matter in terms of total depth of field, only the aperture.

My experience is that with a crop sensor, and the frame filled with a head & shoulders portrait, you would be looking at f/11-f/16 to get the whole head in sharp focus. At f/29 the whole image would look noticeably soft due to diffraction - perhaps this is what you're seeing.

yes, I'm thinking diffraction must be the problem...I shot a test at f7.1 and the image was way more sharp, so I'm thinking about possibly a Dx ( small chip lens) on a full frame FX body to get the 1.5 magnification might work...
a 70mm becomes a 105mm but has the DOF attributes of a 70.
Thanks for all the help!

I am probably being daft here, but I understood that changing a lens from a DX to FX body does not increase the focal length of the lens. It just crops the ends of the image off, so you still have a 70mm lens, only with the ends of the photo missing and with more pixels stuffed into the sensor. Also using a DX lens on a FX body will result in a lens with insufficient coverage fo thr FX chip, though you may mean using a DX and FX compatible lens.

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Originally Posted by ewax1

yes, I'm thinking diffraction must be the problem...I shot a test at f7.1 and the image was way more sharp, so I'm thinking about possibly a Dx ( small chip lens) on a full frame FX body to get the 1.5 magnification might work...
a 70mm becomes a 105mm but has the DOF attributes of a 70.
Thanks for all the help!

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Won't work, or help your depth of field issues for the reason outlined above.

Doesn't seem like you've fully grasped how depth of field works, but if you're shooting head and shoulders at f/16 and not getting enough depth of field for the head, OR getting usably sharp images, there is something else wrong.

Quote:

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Originally Posted by ewax1

yes, I'm thinking diffraction must be the problem...I shot a test at f7.1 and the image was way more sharp, so I'm thinking about possibly a Dx ( small chip lens) on a full frame FX body to get the 1.5 magnification might work...
a 70mm becomes a 105mm but has the DOF attributes of a 70.
Thanks for all the help!

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No. A 70mm lens is always a 70mm lens. Period.
As has been pointed out, there are two variables that will change the DOF, they are aperture and reproduction ratio. That's it. There's also a good chance the Dx lens won't cover the Fx chip in which case the 70mm lens becomes useless. Also, taking the 70mm lens from a Dx to an Fx format will increase it's angle of view, not decrease it - assuming it covers.

All of this is covered on the homepage of this site.

I've used the Nikkor AF-S 105 F/2.8 VR on both a D2 (1.5 crop) and D3X for portraiture and never had issues at F/8~F/10. I find at F/8 the depth of field is almost perfect for portraits, its a great focal length and a great lens for portraits.

In relation to it being a macro lens and therefor not suited to portraits, perhaps people need to use one before saying that. The focus cam is not linear in the new 105. Manually focusing it for portraits is easy, for macro its easy too.. Using it in AF-S mode for portraits with the focus limiter turned on (so it wont hunt for focus anything below 1m) is sensational. Especally on a D3X, D3s, D700 or D300 that will actively seek out a face and focus for the eyes..

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Originally Posted by alexn

In relation to it being a macro lens and therefor not suited to portraits, perhaps people need to use one before saying that. The focus cam is not linear in the new 105.

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That's all well and good, but the OP is most likely not using the new 105. It was described as a "100mm macro lens". It may or may not be a Nikkor, but the only 100mm macro Nikkor that I am aware of is the old Series E lens. And most macro lenses provide greater manual fine focus capability in the macro range, leaving manual fine focus at portrait range not as nice as a non-macro lens.

digital cameras have about 1/3 less DoF than film formats of the same size. It's the primary reason that Nikon and others removed the DoF scales from their camera lenses after they went into DSLR production - the info wouldn't be accurate going back and forth between film and digital. They could have put two different scales on the lenses, but the marketing people, at the time didn't want the (amateur consumer) to know of the difference. When using an older AIS prime on the FX format - check the DoF vs the DoF scale info. I asked NPS about this issue years ago And they told me I was correct. They confirmed the 1/3 number. It has to do with the way light strikes silver vs how it strikes pixel sites. The light has to be at 90deg to the pixel site - where off angle light hitting silver deposits will react at a wider angle of acceptance. Some designers have experimented with pointing the pixel sites at off 90 to emulate film, but this eats up MP real estate and that isn't good for the marketing folks in the pixel race.

Hopefully, better sensors will solve some of these issues.

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Originally Posted by Yardley

digital cameras have about 1/3 less DoF than film formats of the same size.

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This is not true at all. DOF is dependent on 3 things: focal length of the lens, the f-stop, and camera-to-subject distance. The capture media is not a factor when sensor size equals film size. In a cropped sensor, DOF actually increases if field of view is matched (because focal length changes; it still has nothing to do with capture media - you could accomplish the same change in DOF by capturing on film using the same focal length and then cropping the image).

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Originally Posted by Greg Miller

This is not true at all. DOF is dependent on 3 things: focal length of the lens, the f-stop, and camera-to-subject distance. The capture media is not a factor when sensor size equals film size. In a cropped sensor, DOF actually increases if field of view is matched (because focal length changes; it still has nothing to do with capture media - you could accomplish the same change in DOF by capturing on film using the same focal length and then cropping the image).

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I think Yardley is referring to the idea that film grain is thicker and more uneven than the photosites on a digital sensor, and that film therefore captures (marginally) more of the "spread" of the focus and so gives the impression of more depth of field.

I don't know if this is true. Sounds somewhat plausible theoretically but like many things, I've read about it on the net and never seen it demonstrated.

I didn't even know that a digital Nikon is a large format camera.

Could it be this is the wrong place/forum for you?

Anyway, though I don't shoot digital, I shoot film, and from time to time with a F4s and a 2.5/105 mm. Stopping down a bit gives plenty DoF for portraits - at (what you call) 'full frame' (which we call it toy format :cool:). A crippled sensor like yours should definitely deliver more DoF. If I were you, I'd send the camera and lens to the next service station, really.

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Originally Posted by Greg Miller

DOF is dependent on 3 things: focal length of the lens, the f-stop, and camera-to-subject distance.

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And the size of the circle of confusion that is accepted as being "sharp". This is mainly a matter of definition, but for different formats, different sizes of coc are commonly used.

Try the brenizer method on Portrait and you get the large Format feel you are looking for

Greetings Luke