Help with taking large group photo

[TheRandomMrs]

I'm not new to photography, but I am best in natural light with less than four people. My SIL asked me to take indoor pictures of her combined family of 38! I agreed and am worried about keeping everyone in focus. I plan to use a tripod and figure I will be safe with an aperture of f/8. Is there a particular lens you would recommend or another aperture? I am looking to more experienced (wedding?) photographers for as many tips as possible. Please help me feel more confident! Thank you in advance!

 

[TCampbell]

Although depth of field (DoF) increases as you use higher f-stops, DoF _also_ naturally increases when you use wide-angle focal lengths. You can use fairly low f-stops when using a wide-angle lens and still have a fairly large DoF.

You didn't indicate which camera & lens you will be using.

However... with a typical DSLR, the "kit" lens is almost always an 18-55mm f/3.5-5.6 lens.

Using this lens on a DSLR using the 18mm focal length (the widest angle the lens can achieve), EVEN at f/4 the "hyper-focal distance" is 14 feet (the distance at which the maximum area is in focus) where everything from 7 feet to infinity will be in "acceptable" focus.

Focus on someone in the middle of the pack (or just slightly forward of the middle) and you should be fine.

As this is an "indoor" shot, I'm assuming you'll be using natural light. That means you should probably use the "Aperture Priority" mode, set the aperture to f/4 and then tell everyone to try not to move (because it'll probably be a long-ish exposure time). You can increase the ISO to reduce the shutter exposure time (e.g. maybe ISO 800). As I have no idea what camera you have and how it behaves at higher ISO speeds I hesitate to suggest you use a high ISO value. Most modern cameras do fine at ISO 800 (very low noise and often so low as to not be very noticeable). At ISO 1600 some cameras have more noticeable noise. By ISO 3200 many camera has noise which is quite noticeable. Basically you want to use the lowest ISO value you can get away with using, but if it requires excessively long shutter speeds that anyone who doesn't hold still will be blurred.

 

[TheRandomMrs]

I'm sorry...my camera is a Canon 7d and I will probably use my Tamron 28-70mm f/2.8 lens. I was thinking of renting a Canon 16-35mm f/2.8 just to be safe because it might be busy and tight. I was taking some test shots the other day and my ISO might have to be around 1600 in the darker areas. I also have a 430 EX speedlight, but am not sure of using it (I don't have anything to bounce it off of for that large size of a group...maybe I should get a dome diffuser?).

So you are saying that i should still be able to get 38 people in focus at f/4? Doesn't it help to achieve better focus at a large aperture if i stand back as far as I can? I am just worried that I might have to be close to them in the setting (10-15 ft).

 

[KmH]

For 38 people, 1 - 430EX speedlite won't cut it. For that many people you would likely need at least 3 430EX speedlites.

DoF results from a number of factors, lens aperture being just one of them.
Point of focus distance from the camera also has a big effect on the DoF. The further from the camera the point of focus (PoF) is, the deeper the DoF becomes.

As Tim mentions, lens focal length also plays a part.

Note that DoF calculators need to know 4 things - the image sensor size (what camera is being used), lens focal length, PoF distance, and lens aperture - A Flexible Depth of Field Calculator

Using that calculator: (Canon 7D (1.6x crop factor), 24 mm focal length, f/4 lens aperture, 20 foot focus distance)

Closest acceptable sharpness: 10.85 feet
Furthest acceptable sharpness: 127.67 feet
Total Depth of Field: 116.82 feet

DoF is one of the more difficult technical photography concepts inexperienced photographers have to come to grips with.

 

[TheRandomMrs]

Kim, thank you so much! That is super helpful. You are right about the DOF concept. Like I said, once I get out of my comfort zone of a large aperture and just a few people, I get a little confused and self doubting.