Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Reply
 
Thread Tools Search this Thread
Old Jul 27, 2004, 12:18 PM   #1
Senior Member
 
minutephotos.com's Avatar
 
Join Date: Jul 2004
Posts: 344
Default

:?There seems to be mixed information on this topic. I have heard some say for portraits you want to have a telephoto lens and distance from the subject to get a good blur affect. However, I have heard others say use a wider aperture. Which is correct? I am trying to decide between a Canon 70-200 F4L or a Canon EF 50 1.8L combined with maybe a EF 85 1.8L primes for Portrait work. I primarily shoot outdoors portraits so light or distance is not a big issue.




minutephotos.com is offline   Reply With Quote
Sponsored Links
Old Jul 27, 2004, 1:01 PM   #2
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

The short answer: For a shallower depth of field (for blurring backgrounds), buy the lens with the largest aperture setting (smallest f/stop number), provided it meets your other requirements (able to shoot at a convenient distance to subject for the conditions, lens quality at the focal length and aperture you'll be using it at, etc.).

Danny, Depth of Field is based on Aperture, Focus Distance, andFocal Length.

The larger the aperture (smaller F/Stop numbers), and the closer you are to your subject (focus distance), and the more zoom you use (actual focal length), the shallower your Depth of Field. All 3 variables effect it.

Now, in "real life", in orderfor the subject to take up the same amount of the frame with a longer focal length lens, you'll need to be further away. So, any benefit from a longer focal length lens is cancelled out.

Let's take3 examples....

You are shooting with a 50mm lens using an aperture of f/4 at a focus distance of10 feet. In this case, the range of acceptable sharpness would be from around 8.74 to 11.7 feet (almost 3 feet of acceptable sharpness).

Now, you switch to a 100mm lens using the same f/4 aperture. So, in order for your subject to occupy the same percentage of the image, you need to shoot the shot from 20 feet away (versusfrom 10 feet away, as you did with the 50mm lens).

In this case, the range of acceptable sharpness would be from around 18.7 feet to 21.6 feet. (again, almost 3 feet of acceptable sharpness).

So, we try a 200mm lens now using the same f/4 aperture. So, in order for your subject to occupy the same percentage of the frame, you'll need to shoot from 40 feet away (versus from 20 feet, as you didwith the 100mm lens).

In this case, the range of acceptable sharpness would be from around 38.6 feet to 41.5 feet (again almost 3 feet of acceptable sharpness).

Get the picture (pun intended). :-)

Load this Depth of Field Calculator and selecta camera model. Then, plug in thefocal length ofthe lens (or focal length setting for the amount of zoom you're using), focus distance and aperture to calculate Depth of Field.

http://dfleming.ameranet.com/dofjs.html

Experiment with this Calculator, and you'll get a better idea how these parameters (Aperture, Subject Distance and Focal Length), impact the amount of a photo that is in focus.

You'll find that the lens with the largest available aperture setting (smallest f/stop number) will have the shallowest depth of field, provided your subject is occupying the same percentage of the frame.

What you are shooting for, is to make sure your subject is within the DOF, and the background is not (so you'll need to put some space in between your subject and the background for best results -- the more the space - the more blurred it will become).

BTW, DOF calculations are always based on the actual focal length of the lens, not the 35mm equivalent focal length (which will belonger with cameras that have sensors smaller than a 35mm film frame).

Here is a good article on DOF that you may want to read:

http://www.luminous-landscape.com/tu...ries/dof.shtml



JimC is offline   Reply With Quote
Old Jul 27, 2004, 3:22 PM   #3
Senior Member
 
RyanH's Avatar
 
Join Date: Dec 2003
Posts: 452
Default

This is what I was taught, and of course it does not mean it is right.

Use a telephoto lens and zoom in on the subject. Also open up the aperture as much as you can without getting too much light. You also need to make sure your subject is not directly in front of the background you wish to blur.
RyanH is offline   Reply With Quote
Old Jul 28, 2004, 2:00 AM   #4
Senior Member
 
minutephotos.com's Avatar
 
Join Date: Jul 2004
Posts: 344
Default

Thanks, you seem to know a lot about photography. I seem to be learning the expensive way., by buying thelowest price item first and then upgrading. Now I am reserching first then spending... I really want the 70-200 F4L because I can get it now, but I suspect just like the 55-200 I have now, I soon find the need for a 2.8L or F2.8L IS. So to get more familiar with faster lens I am thinking about getting the 50 1.8. Is it true that optically the 50 1.8 is equal to the 70-200 F4L or 2.8L. Since the lens is capable of an aperture of 1.8 does that make it better at 2.8 or F4? Can you really bump the ISO up to 800 on a Canon Rebel or 10D with a F4 instead of buying a 2.8?

Through reserch I have also concluded I have to have a 50 1.8. At $79.00 USA or $64.00imported(whats the difference), B&H Photo. Do they really have them in stock?
minutephotos.com is offline   Reply With Quote
Old Jul 31, 2004, 6:42 PM   #5
Senior Member
 
minutephotos.com's Avatar
 
Join Date: Jul 2004
Posts: 344
Default

Here are some samples after working on this forum and listening to all tha advice.

http://www.photo.net/photodb/folder?folder_id=417633

What I am having problems with now are priniting. When I shoot at full resolution on the Digital Rebel I have to crop about 1 1/2 inches off original to get it cropped to 8X10. How can I get what I frame in the camera to be 8X10 size so I don't cut offpart of picture.


minutephotos.com is offline   Reply With Quote
Old Jul 31, 2004, 10:47 PM   #6
Senior Member
 
Alan T's Avatar
 
Join Date: Jun 2003
Location: Chester, UK
Posts: 2,980
Default

minutephotos.com wrote:
Quote:
I primarily shoot outdoors portraits

Blurring the background is just one of the issues in portraiture. An old-fashioned 'portrait' lens would be 80-85mm for a 35mm film frame. The idea was not to distort facial features (in head & shoulders) by being a bit further away than with a standard (50mm) lens. So why not use both telephoto and wide aperture?

And the wonderful thing is with digicams that if you can find a willing model (e.g., dog or child tiedto a post (don't try it with the wife)) you can experiment to your heart's content without it costing anything.
Alan T is offline   Reply With Quote
Old Jul 31, 2004, 10:53 PM   #7
Senior Member
 
Alan T's Avatar
 
Join Date: Jun 2003
Location: Chester, UK
Posts: 2,980
Default

minutephotos.com wrote:
Quote:
cropped to 8X10. How can I get what I frame in the camera to be 8X10 size so I don't cut offpart of picture.

You can't. You'll have to imagine the 5:4 aspect ratio superimposed on your camera's 3:2 or 4:3 ratio, and do the cropping afterwards on your computer with an image editor. It might help if you make yourself a 5:4 hole cut in a card, and hold that up to the subject to judge how to frame the subject.
Alan T is offline   Reply With Quote
Old Jul 31, 2004, 11:00 PM   #8
Senior Member
 
minutephotos.com's Avatar
 
Join Date: Jul 2004
Posts: 344
Default

You are the second person to tell me this so I am sure it is true. My Sony F707 did this very well.However, going back to that from my digital rebel is not an option. What do you mean 5:4 cut in card for framining. I get the idea and understand that I need to see what will print at 8x10 other wise I will be guessing at framing during each shot. How do you suggest making the 5:4 hole, and how big should the whole be? i think once I get some practice in I will eventually be able to do it by eye.
minutephotos.com is offline   Reply With Quote
Old Aug 1, 2004, 4:23 AM   #9
Senior Member
 
Alan T's Avatar
 
Join Date: Jun 2003
Location: Chester, UK
Posts: 2,980
Default

minutephotos.com wrote:
Quote:
What do you mean 5:4 cut in card for framing..... How do you suggest making the 5:4 hole, and how big should the whole be?
Well I'd use a pair of scissors or a sharp knifeon a piece of old breakfast cereal packet, and try a few different sizes until you get one that you can hold up comfortably about a foot from your eye.

BTW, It seems a shame to me to have a wonderful camera like a Rebel, and constrain yourself *always* to print at exactly 10x8. If you ever try a panoramic view, you'll find it a little tricky!
Alan T is offline   Reply With Quote
Old Aug 1, 2004, 3:41 PM   #10
Senior Member
 
minutephotos.com's Avatar
 
Join Date: Jul 2004
Posts: 344
Default

What do you think about actually drawing these dimensions on the lens filter. I could get a cheap clear filter used just for framing 8x10's and draw with permantent marker or masking tape a square that is set to 5:4. Would this work?

Oh, I would love to print at other sizes, but my Olympus P-440 only does 8X10. I have a Canon S800 Inkjet that can go larger but I never do. Maybe I will try sending some out to ofoto or Snapfish.



Thanks
minutephotos.com is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 5:04 AM.