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simons-photography · 03-27-2008, 10:41 AM

Originally posted by christinelandon

Oh, and avoid use of coffee, tea, chocolate, and other caffeine-containing drinks/foods until after your shoot!

yes thats an interesting consideration

JrPentax · 03-27-2008, 05:15 PM

hi there christinelandon - i am really appreciative of that post, and thankyou so very much for the advice, the drinks/foods issue is probably a big one for me, thankyou very much for pointing it out.

after reading your post... i have a 70-300 lens that i have been using, and i am wondering would i get better DOF using that at 70 then i would if i was to use the 18-50 at 50 (yes i can take a few steps backwards to get further away)

thanks very much again - lots of usefull tips there :-)

christinelandon · 03-28-2008, 01:36 AM

JrPentax, DOF is a product of the interaction of several elements of lens design, one of which is focal length. Another is aperture. In general, shorter focal lengths can yield greater depth of field, as can smaller apertures. So, a 50mm FL can give greater depth of field than a 70mm, and f/16 gives greater DOF than f/2.8. These factors interact, so you expect great depth of field from an 18mm–f/16 combo, and shallow depth of field from a 300mm–f/4 combo.

creampuff · 03-28-2008, 01:56 AM

Aside from focal length and shooting aperture, DOF is also a function of subject distance too.

christinelandon · 03-28-2008, 02:27 AM

Creampuff, true enough!

Geekybiker · 03-28-2008, 08:51 AM

Focal length has nothing to do with DOF. Actual DOF is virtual unchanged
DOF2

The main difference is that background elements appear larger- perspective is compressed so apparent DOF is lessened.

simons-photography · 03-28-2008, 10:22 AM

Originally posted by Geekybiker

Focal length has nothing to do with DOF. Actual DOF is virtual unchanged
DOF2

The main difference is that background elements appear larger- perspective is compressed so apparent DOF is lessened.

I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house

egordon99 · 03-28-2008, 10:26 AM

????????
In comparison to a shot of the farmhouse with what other focal length/f-stop? And did you change the distance between the camera and subject?

Also, your 70-300mm doesn't open up to f/4 at 300mm. It's maximum f-stop is f/5.6 at 300mm.

Originally posted by simons-photography

I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house

simons-photography · 03-28-2008, 11:34 AM

Originally posted by egordon99

????????
In comparison to a shot of the farmhouse with what other focal length/f-stop? And did you change the distance between the camera and subject?

Also, your 70-300mm doesn't open up to f/4 at 300mm. It's maximum f-stop is f/5.6 at 300mm.

ah well it must have been at 5.6 then but the farm house was well let me see 1 mile away ? not sure its across 3-4 feilds not exactly a case of changing subject to camera distance....

Geekybiker · 03-28-2008, 12:06 PM

Originally posted by simons-photography

I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house

Regardless of how positive you are, experimental evidence (the link I posted) and the math of optics say otherwise. DOF as an objective measurement does not vary significantly (that is the range in which which circles of confusion below a set limit).

Goto any DOF calculator and you'll see.

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03-27-2008, 10:41 AM	#31
simons-photography Veteran Member Join Date: Dec 2007 Location: Northamptonshire - England Photos: Gallery Posts: 496	Originally posted by christinelandon Oh, and avoid use of coffee, tea, chocolate, and other caffeine-containing drinks/foods until after your shoot! yes thats an interesting consideration

03-27-2008, 05:15 PM	#32
JrPentax Forum Member Join Date: Jan 2008 Location: Melbourne, Australia Photos: Gallery Posts: 93 Original Poster	hi there christinelandon - i am really appreciative of that post, and thankyou so very much for the advice, the drinks/foods issue is probably a big one for me, thankyou very much for pointing it out. after reading your post... i have a 70-300 lens that i have been using, and i am wondering would i get better DOF using that at 70 then i would if i was to use the 18-50 at 50 (yes i can take a few steps backwards to get further away) thanks very much again - lots of usefull tips there :-)

03-28-2008, 01:36 AM	#33
christinelandon Veteran Member Join Date: Jan 2008 Location: Seattle, Washington, USA Photos: Gallery Posts: 812	JrPentax, DOF is a product of the interaction of several elements of lens design, one of which is focal length. Another is aperture. In general, shorter focal lengths can yield greater depth of field, as can smaller apertures. So, a 50mm FL can give greater depth of field than a 70mm, and f/16 gives greater DOF than f/2.8. These factors interact, so you expect great depth of field from an 18mm–f/16 combo, and shallow depth of field from a 300mm–f/4 combo.

03-28-2008, 01:56 AM	#34
creampuff Veteran Member Join Date: May 2007 Location: Singapore Photos: Gallery Posts: 3,953	Aside from focal length and shooting aperture, DOF is also a function of subject distance too.

03-28-2008, 02:27 AM	#35
christinelandon Veteran Member Join Date: Jan 2008 Location: Seattle, Washington, USA Photos: Gallery Posts: 812	Creampuff, true enough!

03-28-2008, 08:51 AM	#36
Geekybiker Veteran Member Join Date: Feb 2008 Location: Chicagoland Posts: 337	Focal length has nothing to do with DOF. Actual DOF is virtual unchanged DOF2 The main difference is that background elements appear larger- perspective is compressed so apparent DOF is lessened.

03-28-2008, 10:22 AM	#37
simons-photography Veteran Member Join Date: Dec 2007 Location: Northamptonshire - England Photos: Gallery Posts: 496	Originally posted by Geekybiker Focal length has nothing to do with DOF. Actual DOF is virtual unchanged DOF2 The main difference is that background elements appear larger- perspective is compressed so apparent DOF is lessened. I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house

03-28-2008, 10:26 AM	#38
egordon99 Inactive Account Join Date: Dec 2006 Location: Outside of Philly Posts: 1,561	???????? In comparison to a shot of the farmhouse with what other focal length/f-stop? And did you change the distance between the camera and subject? Also, your 70-300mm doesn't open up to f/4 at 300mm. It's maximum f-stop is f/5.6 at 300mm. Originally posted by simons-photography I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house

03-28-2008, 11:34 AM	#39
simons-photography Veteran Member Join Date: Dec 2007 Location: Northamptonshire - England Photos: Gallery Posts: 496	Originally posted by egordon99 ???????? In comparison to a shot of the farmhouse with what other focal length/f-stop? And did you change the distance between the camera and subject? Also, your 70-300mm doesn't open up to f/4 at 300mm. It's maximum f-stop is f/5.6 at 300mm. ah well it must have been at 5.6 then but the farm house was well let me see 1 mile away ? not sure its across 3-4 feilds not exactly a case of changing subject to camera distance....

03-28-2008, 12:06 PM	#40
Geekybiker Veteran Member Join Date: Feb 2008 Location: Chicagoland Posts: 337	Originally posted by simons-photography I don't quite think so I shot a distant farm at 300 mm with F4 and I'm positive that some parts are less in focus than the actual farm house Regardless of how positive you are, experimental evidence (the link I posted) and the math of optics say otherwise. DOF as an objective measurement does not vary significantly (that is the range in which which circles of confusion below a set limit). Goto any DOF calculator and you'll see.

zoom stability...

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