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.
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.
Won't work, or help your depth of field issues for the reason outlined above.Originally Posted by ewax1
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.
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.
One man's Mede is another man's Persian.
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..
Chamonix 045N-2 - 65/5.6 - 90/8 - 210/5.6 - Fomapan 100 & T-Max 100 in Rodinal
Alexartphotography
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.
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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