A Quick DOF lesson
 

Assuming you don't want to post-process all your DOF needs, here's how to achieve shallow depth of field optically:

f/2.8 isn't large enough unless the focused and non-focused area are farther apart than I see in this picture. For a human body to both in and out of focus, I would go at least to f/1.8, and 1.4 if you can.

Wide angle lenses won't work too well. Although a tele lens in needed, the factor that really determines DOF is the ratio of how far away the out of focus are is to the focused area, relative to the ratio of the how far away the focused are is to the lens. In other words, if you're 200 feet away from the in focus subject, and the intended defocus are is only 2 feet, it won't be very much out of focus--that's only 1%. However, if you're much closer, like 10 feet away from the focused area, the intended defocus area still 2 feet, that's fully 20%. That should really throw the background out of focus, especially with a f/1.4 lens.

Given the environment in this pic, 50mm, which has the same field of view as a 75mm lens on a cropped sensor, could work fine if you're 8-12 feet away. Bottom line, get as close as you can without resorting to wide angles and try to fill the frame.

Shutter speed doesn't have anything to do with DOF whatsoever. But obviously it's important for proper exposure, which is always fundamental.v:2 cents::2 cents::2 cents: 6 cents baby

:pimp:pimp

No picture for me here, cant see that picture

good stuff!
:thumbsup

Out of the fucking way people! Professional coming though.... :thumbsup:thumbsup

Does this one have DOF or just strange blur?

I actually removed the lens and held it up backwards to emulate a macro lens. That's why it shows the aperture at zero.
http://www.retnuh.com/files/echinacea.jpg

no shit eh. now i just have to find a f/1.4 telephoto! i'm thnkng of picking up the 85mm f/1.8

the only nikon lens i can find with 1.4 is a 50mm

LOL, thanks for the props, you and 2 others. I hope it helps explain DOF better. :thumbsup I'm actually not a professional, though I shoot like one! :winkwink:

Hey man. You can get a Sigma 30mm that has an f/1.4 that works for Nikon and I think they have a Canon mount too. The 50/1.4 is a great lens if you can drop the benjamins on it.

The 85/1.8 is an outstanding lens. I might get one but for now, an 80-200/2.8 meets most of my needs. And I have a 50/1.8 so if I need 85mm and f/1.8, I use the 50mm, and walk backwards!:pimp

Don't sweat it if you can't drop the cash on an f/1.4. I think you can get a 50/1.8 for around $125. A 1.4 costs a lot more, but often is worth it.

f1.8 - 85mm is a fine prime lens...
good luck with it and dont forget to show us the outcome of your studies.

Low depth of field (blurry back ground) is created by;

Long focal length + wide aperture + fast shutter speed (200MM, f2.8, 2000th sec @ 200 ISO)

High depth of field (crisp image throughout) is created by;

Shorter focal length + narrow aperture + slower shutter speed (50 mm, f11, 125th sec @ 200 ISO)

Hope that helps :)

thanks for the input! i did find the 85mm f1.4 from nikon is available as well, but quite pricey. i am goging to keep with my 18-105mm f/3.5 vr for now and perhaps get the 85mm after i sort out my shooting style.

still getting DOF sorted out for HD video as well, it's a whole nother level! LOLOLL

Get the discount f/1.8 primes you'll love them. With the 18-105mm, I'll assume you have the Nikon D90 (since that's the lens that comes with the kit).

Cheap in price but not in quality:
- Nikon 50mm 1.8 ~ $125 (for the price, the quality of this lens cant be beat )
- Nikon 35mm 1.8 ~ $200 (a good, unobtrusive walk around lens for a cropped sensor DSLR like the D90.. will give you a near WYSIWYG field of view)

Easily done in photoshop, you can do it manually in ps using the built in tools, but there are plugins such as onOne Phototools and TopazAdjust that will do it automatically as well. It's a five second job to do a focal point effect like that.

If it's a 5 second job then it sounds like it doesn't allow you to "recreate" the dimension of depth? 2 or 3 levels of different radius blur reminds me of a cartoon. :2 cents:

is this kind of what your referring to?

http://www.littlemutt.com/holly_van_hough.jpg

Some examples of depth of field application;

Narrow depth of field: Shot with a Canon 20D, f2.8, 80mm, 2000th sec, 200 ISO

You can notice that shapes in the background of the image are starting to take on the shape of the lenes aperture setting. At f2.8, the aperture is basically a circle, with slightly flat edges -- and in this image we can see that the certain specs within the image are taking on the shape of the aperture setting.

http://web.mac.com/timothysvickery/i...ed%20Maple.jpg

Wide depth of field: Shot with a Canon 20D, f8, 100mm, 60th sec, 200 ISO

Much more of this image is in focus, as the camera has had more time to record the information throughout the entire depth of field.

http://web.mac.com/timothysvickery/i...g%20Maples.jpg

Wide open aperture is key. Lens focal length will change the sense of compression in the image, but aperture is what creates bokeh. I don't think there is any substitute for creating the effect in camera.

Indeed, the 85/1.4 is expensive as hell. If you thought you'd need 85mm but are worried about cost, I'd say just get the 1.8 version of the 85mm. 1.4 is almost overkill on 85 since the focal length enhances shallow DOFs.

Yes, keep shooting most of your shit with the excellent 18-105, but please take my advice on this. If you want to learn to be a better photographer faster, you need to experiment with, and learn how to shoot with a fast, fixed lens. Be willing to spend all of $125 on the 50mm/1.8. You simply can't go wrong with that lens! When you do it, you'll thank me. Trust me on this. :2 cents:

:thumbsup Quoted for truth, just like I said. :pimp

Spoken like a photographer!:thumbsup

By the way, this means shooting at the largest aperture the lens is capable of. That setting depends on your lens. For example, if you have a 1.8 lens, you can always "stop down" to a smaller aperture like f/8 (or smaller), but setting it to f/1.8 is wide open.

On your 18-105 lens, it's a different story. That has what's known as a variable aperture. At your widest setting (18mm), it has f/3.5 as its maximum aperture (biggest hole, wide open, etc.) But at 105mm, it can go no larger than f/5.6.

That's the big negative with inexpensive zoom lenses. That and durability. But, many of them are still quite good in overall image quality, especially if you "stop down" and shoot at f/8.:2 cents:

I was just looking through some older pics and found this one I took of my daughter:

http://thsrv.com/p/dof.jpg

Canon 1Ds mkII, 70-200mm F4 IS L @121mm, f4, 1/250th, ISO200

Now tell me you could achieve this effect in post. It's impossible, unless you were able to mask every blade of grass to define their depth... and even then there are some which are not straight and have varying focus along their length. You can't just do it with a simple gradient since for blade X there's multiple blades in front of and behind it in the same (2D) region of the image which have different blur...

Yup, good info coming from this thread - to help explain visually, I just took these two consecutive shots in the garden. They are hot off the camera and never even had a whiff of photoshop... resized in iPhoto, but orig files are linked to.

Nikon D300 w/ Sigma APO 70-200 f2.8 Macro with both photos taken at 145mm


With the aperture as closed as possible @ f22: Note at this aperture in the morning, the shutter speed is quite slow (1/10) so there is motion blur on the flower.

http://borkedcoder.com/images/gfy/DoF/_DSC1738.jpg
Original file



Now, with the aperture fully open @ f2.8 (1/640 sec), the way a blurry background makes the flower stand out is great! Even the flower's leaves which are right next to the flower.

http://borkedcoder.com/images/gfy/DoF/_DSC1737.jpg
Original file

sorry, exposures were 1/20 @f22 and 1:1640 @f2.8
goddam bees ruining my shots :mad::mad::mad:

Surely shallow depth of field is the most overused and abused trick in the book. It's all fine for nature stuff or maybe if you want your model to stand out from the background but who really wants to see half a blurred model? Personally I think this sucks!

hot pics ..

I shoot with the 85 1.4. not sure why you can't get one?

thx for all the input! good stuff

in large, i agree. here is the original shot i was inquiring about. i was more impressed with the very narrow dof, it appears to be <1". i don't think it works for this shot though (why blur the pussy out?)
http://www.alsscan.dvdsuperstar.com/images/10.jpg


nevertheless, i wanted to gain some knowledge on how to achieve the narrow dof

well, 2 reasons.

1. the camera shop where i was looking at lenses did not have the 85mm 1.4 listed.
2. it's crazy expensive! 3x+ more $ than the 1.8.

does half a stop make 3x+ the diff? prolly so but i can't justify the purchase right now.
:thumbsup

Not sure what glass you use, but you can pick up a 50mm Nikon 1.4 for about $200. Amazing lens for the money.

i hear ya. y'all remind me of my photog instructor back in college, lol. in fact, i had a 50mm1.4 on my minolta xd5 at that time.

anyhoo, i found a couple used 85mm 1.8 on craigslist, $250ish. certainly a great price if the lens has been taken care of. i;ll have to manually focus as my af doesn't work with it. nothing wrong with that of course.

:thumbsup

Since it doesn't manually focus, I'm guessing you have a D40/D60?

If that's true, ALL AF-D (or earlier) lenses don't autofocus. It's one reason why I use a D300, and you'd at least need a D80/D90 level camera to get autofocus on older lenses. I love autofocus so I can just concentrate on composition, etc., so in your case, I would get the $200 35mm/1.8, and this 85mm you want.