70-200 afs vr DOF question

[jeanie]

hi,
got a question for all.

if i use the above lens at 200mm f2.8, subject about 5-8 meters away, will i get 'eyes sharp, ears blur'?

if so, then if i use f8(for example), will the picture turn out to be the same (i'm referring to bokeh, DOF) as comparedto if i use 18-200mm at 200mm at f8?

[psychobiologist]

plug in the values~

http://www.dofmaster.com/dofjs.html

at the distance of 15 feet or 5 metres at f2.8 at 200mm you get 0.2feet or 6cm between the nearest and furthest point of acceptable sharpness

will probably need to focus very accurately to utilize this 6 centimetres well

at f8, distance of 15 feet, you have abt 0.6 feet between the nearest/furthest points of acceptable sharpness.

on paper i suppose both the 70-200 and the 18-200 will give the same "type" of image, i.e. if you focus at the right point the right areas will be sharp, but the bokeh will be different....

[jeanie]

thanks for the link and the brief expla.

so, assuming i'm shooting a wedding, must i memorise all the values calculated first before i even think of using the 70-200?
i dont think i have the time to check every single image in the LCD as i'm a trigger happy person.

[psychobiologist]

Originally Posted by jeanie thanks for the link and the brief expla. so, assuming i'm shooting a wedding, must i memorise all the values calculated first before i even think of using the 70-200? i dont think i have the time to check every single image in the LCD as i'm a trigger happy person.

hmm.. its too much to memorize. just as a rough gauge know approximately at a certain distance away, how much depth of field you will approximately be having..

f2.8 at 70mm on object 5 metres away iyou get a total depth of field of over 1.56ft (45+cm), but at 100mm it goes down to abt 20cm, 150mm abt 10cm and at 200mm 6cm. 6cm is enough for nose/face but the ears wont be sharp.

double the aperture, from 2.8 to 5.6, you will get double the total depth of field at 5metres, e.g. 70mm at 5 metres f2.8 depth of field is 1.56feet, at 70mm f5.6 its twice, 3.13ft.


5 metres, 200mm, f2.8. if you focus on the nose, the 6 cm total depth of field would mean 3 cm infront of the nose and 3 cm behind the nose, i.e. the face.. the ears wont be in.

grab a friend and do test shots, find out what are the critical distances, e.g. just a fictional example..when people are less than 3 metres away 70mm should be used and no more than that etc, when using higher zooms at wide open, which part of the face is best used for focus.. i.e. the eyes or specs, or the nose? lips etc..

[LiewTL]

You can also use the depth-of-field preview button on your camera for a quick check.

[jeanie]

Originally Posted by psychobiologist hmm.. its too much to memorize. just as a rough gauge know approximately at a certain distance away, how much depth of field you will approximately be having.. f2.8 at 70mm on object 5 metres away iyou get a total depth of field of over 1.56ft (45+cm), but at 100mm it goes down to abt 20cm, 150mm abt 10cm and at 200mm 6cm. 6cm is enough for nose/face but the ears wont be sharp. double the aperture, from 2.8 to 5.6, you will get double the total depth of field at 5metres, e.g. 70mm at 5 metres f2.8 depth of field is 1.56feet, at 70mm f5.6 its twice, 3.13ft. 5 metres, 200mm, f2.8. if you focus on the nose, the 6 cm total depth of field would mean 3 cm infront of the nose and 3 cm behind the nose, i.e. the face.. the ears wont be in. grab a friend and do test shots, find out what are the critical distances, e.g. just a fictional example..when people are less than 3 metres away 70mm should be used and no more than that etc, when using higher zooms at wide open, which part of the face is best used for focus.. i.e. the eyes or specs, or the nose? lips etc..

thanks man.link was a great help.

[eastwest]

If you take a picture with 70-200 f8 vs 18-200 f8 at same distance you will get the same DOF but the pictures will definitely be different. IMO 70-200VR gives some of the best contrast and colours of any of the Nikon lens line-up. Expensive lenses don't just give you f2.8 they give you quality in other areas too.

[jeanie]

Originally Posted by eastwest If you take a picture with 70-200 f8 vs 18-200 f8 at same distance you will get the same DOF but the pictures will definitely be different. IMO 70-200VR gives some of the best contrast and colours of any of the Nikon lens line-up. Expensive lenses don't just give you f2.8 they give you quality in other areas too.

ok.got it.
i guess it's well worth the weight.

[jeanie]

Originally Posted by LiewTL You can also use the depth-of-field preview button on your camera for a quick check.

i dont think i have enough light indoors to use the DOF preview.

[lsisaxon]

Originally Posted by jeanie thanks for the link and the brief expla. so, assuming i'm shooting a wedding, must i memorise all the values calculated first before i even think of using the 70-200? i dont think i have the time to check every single image in the LCD as i'm a trigger happy person.

You don't have to but once you know your lenses well, you'll know what aperture to use to give you certain DoF.

[jeanie]

Originally Posted by lsisaxon You don't have to but once you know your lenses well, you'll know what aperture to use to give you certain DoF.

ya.i should really shoot more.but to be on safe side, i think i'll switch to f4 or 5.6.

just a quick ques,

if this lens at 2.8 produces such paper thin DOF, why did they make 2.8?what diff will it make if they make the max aper at f4?

[lsisaxon]

Originally Posted by jeanie ya.i should really shoot more.but to be on safe side, i think i'll switch to f4 or 5.6. just a quick ques, if this lens at 2.8 produces such paper thin DOF, why did they make 2.8?what diff will it make if they make the max aper at f4?

Some people want that effect. That's why you've got to know what lens to use and for what purpose. Knowing your working distance is very important.