Group Portraits, DOF question with long lens...

[BlueCosmo5050]

I think I understand this correctly but I figured I'd ask here first. If I was to shoot a group photo at F/4 with a 55mm FE of just a few people the background would be slightly blurred, but the people are in focus.

Now let's say I do the same thing at F/4 at 135. Obviously the background is going to be less in focus, but will the group of 2 or 3 people be less in focus if I focus on only one persons eye with a single focus point?

In other words, at a wide angle, if the people aren't even in the focal plane, I may only get one person in good focus, but if I do it a distance, though the background is more out of focus, I will get all 3 people in better focus due to the distance correct? Or am I wrong on this?

I ask this because I am new to long lenses. I have never owned a long lens but am looking to get a 135 now that I am getting more into photography, I have always been into doing mostly video and landscape photography and have never had the need for telephoto.

135 F2 prime would be preferable over 200 F2 prime right? For portraits?

 

[DonHF]

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

As far as the 125 vs 200 it really depends on the look you want. Keep in mind that the longer the lens the further away you have to go so space can be limiting many times.

 

[Sh_la_m]

I think you are partly correct, but let me try saying it this way:

For group photos, when you are picking an f-stop, you need to consider the focal length of the lens, how far away you are going to be from the group, and whether the people are all going to be in the same focal plane.

If your distance from the group and the focal plane are the same in each shot, you will get more depth of field at the same f-stop with a wider lens than a longer lens.

The further you are away from the group, the more depth of field you can achieve with any lens. If you are far enough away with a longer lens, yes, you may achieve greater depth of field at a some given f-stop than if you are up very close with a wide angle lens.

Focus misses will be more apparent if you are shooting head and shoulders rather than full bodies. A 200MM focal length puts you very far from your subjects unless you are doing pretty much head and shoulders shots, and it is difficult to communicate with your subjects.

hope this is helpful...

 

[BlueCosmo5050]

Lets say I'm at 135mm, if I am shooting at 2.8 and the background is really blurred on a full frame camera, if I focus and recompose, I have less of a chance of screwing that up over doing the same shot at 2.8 at 50mm and focusing and recomposing correct? From what I'm reading and trying to understand the way the focal plane reacts, it seems that the further away the object is, the less I got to worry about the focusing and recomposing screwing it up.

 

[Sh_la_m]

The answer to the first question is no, it's just the opposite. But yes, if you are further away, the depth of field is greater and the chance of missing focus less.

 

[BlueCosmo5050]

I believe I worded it wrong. What I was saying is, at a distance, such as 135mm, there is shallower depth of field and I can focus and recompose and not have as much error as I would at the same F stop being close to the subject, such as a 35mm or 50mm, correct? So, wouldn't it be better to take the group shot further away so I don't have as much of a chance of missing the focus?

 

[Sh_la_m]

There is a difference between distance from subject and focal length of a lens that I think is getting mixed up. They are two different things. The way you are expressing it, I feel like you are getting it backwards still.

The focal length of a lens, which is described in MM, affects the angle of view, with longer lenses (for example a 135mm) having a narrower angle of view and subsequently shallower depth of field and greater out of focus areas than a photo taken at the same aperture, and from the same distance, with a wider lens (say a 50mm). Distance from subject is just how far you are away from what you are shooting. The farther away from your subject you are, with any lens, the greater depth of field - more in-focus areas- you will have.

So in most cases you have a better chance of getting everyone in focus with a 50mm rather than a 135mm, unless you move much farther away.

 

[Arizona Sunset]

I think I understand this correctly but I figured I'd ask here first. If I was to shoot a group photo at F/4 with a 55mm FE of just a few people the background would be slightly blurred, but the people are in focus.

Now let's say I do the same thing at F/4 at 135. Obviously the background is going to be less in focus, but will the group of 2 or 3 people be less in focus if I focus on only one persons eye with a single focus point?

In other words, at a wide angle, if the people aren't even in the focal plane, I may only get one person in good focus, but if I do it a distance, though the background is more out of focus, I will get all 3 people in better focus due to the distance correct? Or am I wrong on this?

I ask this because I am new to long lenses. I have never owned a long lens but am looking to get a 135 now that I am getting more into photography, I have always been into doing mostly video and landscape photography and have never had the need for telephoto.

135 F2 prime would be preferable over 200 F2 prime right? For portraits?

Depth of field and effective amount of blur is determined by the distance, magnification, and aperture for a given sensor size.

The examples that you gave are really a lot different. Here's the chart for portraits for each:



You have a "normal" (55mm) FOV (not specialized for portrait), and three telephoto examples (135mm, 135mm, and 200mm).

To be honest, if you are starting out, go with the 55mm, and get closer to the subject if you need more blur. Alternatively, an 85mm f1.8 that can be stopped down to f3.5 or f5.6 when groups of people are present is a more versatile choice because it can smooth out backgrounds and isolate subjects a bit better. Also still usable indoors, but can hang with the 135mm outdoors as well. The 135mm is tough indoors, and will compromise lowlight because you'll have to stop down. Not so with the 55mm, just back up and use it wide open at f1.8. The 200mm is in a different league and very specialized - just leave it alone for now.

 

[BlueCosmo5050]

This makes sense. I'm actually not a beginner but I've never been a telephoto shooter. I came into this doing DSLR video. In video it isn't often that telephoto would be used. When I did my portraits I mostly used a 100mm 2.8L but now 135 F/2L.

I've taken group shots at a wide angle before and was wondering what it would be like if I took it a long distance.