Question about focus lengths w/ 1.6 crop for the experts.

[md6040]

I want a lens with a longer focus length that will allow me to shoot portraits w/ a distorted background. That said, I still want it to be in the 50-85mm film equiv range. As well all know, most canon lenses focus lengths are designed for 24X36mm film. So, when I shoot people w/ my 85 f.18 the background isn't out of focus enough for my needs. I have considered going with a 135mm f/2L USM, but I'd really like something I can use in a smaller studio. Plus the bokeh (sp) of the 100mm+ isn't quite what I'm looking for.

It would be ideal if I could find an extremely sharp lens that has a longer range of focus before it ran out and hit infinity. The two lenses I'm really looking at now are the 35 f1.4L and the 24-70 2.8L. Will either of these lenses help my dilemma? Also, is there a name for this when looking at different lenses?


Thanks in advance!

[timmyquest]

All you need to do is stop down the lens if you want the DOF to be larger. Which is what it sound like you need.

The 135mm f/2 is an awsome lens though so dont hesitate getting it if you feel the need for telephoto speed :-D

[md6040]

Man, maybe I didn't make my question clear. This is something that's plagued me ever since the invention of clopped DSLRs. You mean all I had to do is stop it down?! Maybe I'm on the wrong forum. (Focus length isn't DOF btw :lol: )

Thanks though. :)

[robertwgross]

...
It would be ideal if I could find an extremely sharp lens that has a longer range of focus before it ran out and hit infinity.

If you are trying to get the background out of focus, then you need to control the depth of field more. That is accomplished by using a wider aperture, not narrower aperture.

---Bob Gross---

[Aylwin]

Have you considered the 50 f/1.4? With the crop factor, that's within the 50-85mm equivalent you require and f/1.4 should give you enough background out of focus. Plus, the 50 f/1.4 is known for it's good bokeh.

I'm not sure about the 35 f/1.4. For portraits, it might give you odd perspective. :roll: This can easily be tested though.

[md6040]

...
It would be ideal if I could find an extremely sharp lens that has a longer range of focus before it ran out and hit infinity.

If you are trying to get the background out of focus, then you need to control the depth of field more. That is accomplished by using a wider aperture, not narrower aperture.

---Bob Gross---


I know how DOF works. We are not talking absolute basic photography, but thanks.

Haven't you guys ever noticed that by the time you try to shoot a portrait of someone from the wasit up w/ the 1.6 crop you're almost all the way to infinate focus? You can be using f1.8 or f22 and the background is still almost in focus, even if the background is 10ft behind the subject and you're shooting a 85mm lens.

I'm just trying to find one lens that will cure this delima for anywhere below $1500. Maybe I should just buy an Imacon Flextight and use my EOS 1V for some real quality shots using the lenses I have.

[Jesper]

A portrait from the waist up with a 50mm lens on an 1.6x crop factor camera...

Using this lens calculator (http://www.sweeting.org/mark/lenses/), I estimate that you would be about 3 meters from your subject (the angle of view will be about 25 degrees, so that you can frame a subject of about 1.34 meters, or 4 feet, at a distance of 3m).

Then I use this DOF calculator (http://dfleming.ameranet.com/dofjs.html) to see what the depth-of-field will be at different apertures.

f/1.4: 290.8 cm - 309.8 cm (DOF of 19 cm = 7.5 inches)
f/2.0: 287.1 cm - 314.1 cm (27 cm = 10.6 inches)
f/2.8: 282.1 cm - 320.3 cm (38.2 cm = 15 inches)

If the background is 10 feet behind the subject, it will not be in focus!!

[Aylwin]

Haven't you guys ever noticed that by the time you try to shoot a portrait of someone from the wasit up w/ the 1.6 crop you're almost all the way to infinate focus? You can be using f1.8 or f22 and the background is still almost in focus, even if the background is 10ft behind the subject and you're shooting a 85mm lens.

I haven't noticed this myself. I usually get background out of focus enough when I want to. Maybe my definition of "out of focus" is a bit different? Perhaps you can show some samples of what you mean?

For example, the background of the following photos (unprocessed, only size-reduced) are out of focus enough for me:
http://www.cal-family.org/download/CRW_5228.jpg
http://www.cal-family.org/download/CRW_5229.jpg

[md6040]

I know it won't be in focus. :lol:


I think I've made progress in my search.

Example:

When I shoot w/ my 85mm 1.8, I find myself shooting mostly at 15-16ft. The focus runs out at around 18ft. No, it's not in focus when the background is 10 ft behind the subject. I checked out 85mm 1.2 and it focuses out to 35ft or so before it hits infinite focus. It heard it makes a totally different kind of bokeh when shallow DOF is used in 15 ft range. This is neat and all, I just need something between 50-80mm. 50mm is ideal, like the 35mm f1.4 X 1.6= 56mm film equiv.

currently I own the 50mm f1.8 only 'cause it was given to me. I have the same delima with that lens that I do w/ the 85mm f1.8. How does the 50 f1.4 compare? The 35mm f1.4L and 24-70 2.8L are the apple of my eye at the moment

Thanks for your help!

[md6040]

Aylwin- which lens is that?

ps. beatiful child you have there! :)

[Aylwin]

It's the 50 f/1.4 that I mentioned. Those shots were taken at f/2.8. I imagine I'd have problems with DoF had I opened up more.

Thanks for the compliment! That's actually my nephew. He's 3 months older than my daughter (my avatar). :)

By the way, I used to own the 50 f/1.8. It's a good lens and I was happy with it. Of course, with the 50 f/1.4 I'm much happier. :)

[md6040]

Yeah, I probably will buy a 50mm 1.4 sometime soon. When comparing to the 50/f1.8, the extra half stop, metal frame and focus dial don't really mean a lot to me. With that said, what are the advantages I'll benefit from with the 50/f1.4? What made you happier?


It seems like I've used it at one point but I don't remember the results.

[Aylwin]

You're right. Initially, I thought the extra fraction of a stop (and other obvious features) would be significant but actually they're not that big a deal. What I immediately noticed were: sharper pictures, faster auto-focus, and brighter, more vivid and more accurate colors. Plus, the bokeh is apparently better. I say apparently because I haven't actually done first-hand tests to confirm for myself.

Fortunately, someone else has done tests. Check this out: http://www.photo.net/equipment/canon/ef50/

Anyway, I'm happy I upgraded from the 1.8 to 1.4. I was first planning to go wider (35mm or 28mm) but since the purpose was for portraits I was afraid I might have perspective problems with close ups.

[John_T]

MD, take a look here:

http://www.luminous-landscape.com/reviews/lenses/canon_lenses.shtml

http://www.fredmiranda.com/forum/topic2/4950/0#50405

http://www.fredmiranda.com/forum/topic2/4950/0#50405

[Andy_T]

These two links might be interesting for you, especially the sample images:

50 mm: http://www.photo.net/equipment/canon/ef50/
85 mm: http://www.wlcastleman.com/equip/reviews/85mm/

The bokeh of the portrait sample image of the 1.2/85 can only be described as 'priceless' ... :shock:

Best regards,
Andy

[jgbeam]

Here's a shot of my grandson with the 85mm f/1.8 wide open on the 300D taken from 10-15 feet. You can see the DOF quite clearly. The ball in front and the clothing in the rear are out of focus. The face seems to be just forward of focus and the background is nothing but blur.


http://www.imagevenue.com/host/web1/77751_IMG_4546res.jpg


I think the 85 f/1.8 is a superb portrait lens.

Jim

[md6040]

Yes. Try getting that kind of distortion when shooting an adult. Then maybe you'll see what I'm talking about.

[jgbeam]

Yes. Try getting that kind of distortion when shooting an adult. Then maybe you'll see what I'm talking about.

What distortion are you referring to? I don't understand this comment.

Jim

[robertwgross]

What distortion are you referring to?


Yes, what distortion? Or, are we talking about simple background blurring?

---Bob Gross---