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10-12-2012, 12:44 AM   #1
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Indoor portraits of 2+ people, best aperture/F value?

Dear camera people wiser than I...

I have treated myself to a fixed focal lens when it was on sale (pentax, 50mm, F1.4) for portrait indoor low light photography without flash of family and friends at celebrations (or indeed any time I have my camera on me).

Being a relative newbie I have been using auto portrait mode (yes, I know it's naughty to use auto modes, but I'm just starting out here!) which have produced some lovely results, with the classic 'wedding photo' look I've been going for, of someone looking handsome in gentle light with the background all blurry behind them (you know the type).

However I'd like to go off-piste now (ie stop using auto portrait), primarily because whenever I want to take a photo of two people, one will be in focus and the other not, despite being (to me, but obviously not the sensitive camera) in the same depth of field.

I think I've gathered that the thing that dictates this is the aperture/F value, so I was thinking of trying to use aperture priority next time (baby steps before I trust myself to be in control of the shutter speed and ISOs simultaneously too!). As such, I was hoping that someone clever could let me know what sort of F value I should be looking for that with the other settings sorted still gives me that dreamy 'things in background out of focus' look, but doesn't extend that to someone's face that happens to be a few behind or in front of someone else's (and without the flash on as I only have the rabbit in headlight inducing inbuilt flash on the K-r).

Many thanks.

10-12-2012, 01:13 AM   #2
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Hi Meerkat,
In order to create the blurred background and "dreamy" look, you have to be looking for wider apertures (lower f-numbers). f/1.4 will give you that, and a few other steps, but by f/2.8 the "dreamy/glowy" look usually goes away with a 1:1.4 50mm lens. However, going to smaller apertures is what will allow you to have different people in focus (more depth of field).
May I suggest 1 or 2 things...
- review the pictures you made in Auto mode that you like. In the "properties" box (depends on what kind of computer you're using, but you can also check that on your camera itself) you'll find what is called the EXIF metadata. Basically the camera parameters are stored there, you'll find the aperture value used, the speed and the ISO. That will give you a good starting point for further experimenting under similar light settings.
- if the camera you are using is a K-7, K-5 or K-30, why not use the TAv mode? This allows you to control both aperture and speed and let the camera decide on the ISO. It is useful to control speed during an event where people don't pose for you, because they will be moving unpredictably, therefore you usually don't want to use anything lower than 1/125.
Hope this helps!
10-12-2012, 01:24 AM   #3
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Dr Meerkat,

If you are shooting at f1.4, your depth of field, the distance between the closest and farthest thing in focus, is quite small.

Depth of field increases with increasing distance to your subject and with increasing aperture value (f-stop). Doing a search on "Depth of Field" in Google will bring up lots of results. You can find a depth of field calculator here: Online Depth of Field Calculator

At 6 feet to subject and f1.4 you can expect the depth of field to be a mere 3 inches (75mm), so it is easy to get the second person out of focus, At 10 feet distance DoF increases to about 7 inches.

At 6 feet to subject and f2.8 you can expect the depth of field to double to 6 inches (150mm), so it is easy to get the second person out of focus, At 10 feet distance DoF increases to about 14 inches.

Play with the calculator to get a feel for how depth of field changes due to changing subject distance, aperture and also try focal length, try a length other than 50mm for the lens.

Also when you focus on a person make sure you have the eyes in focus. If their head is turned make sure you focus on the front most eye.

Regards

Chris Stone
10-12-2012, 03:52 AM   #4
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For me, aperture values can be confusing because of the terminology...f/1.4 could be considered small (numerically) or large (optically). So I just like to say that lower numerical aperture values will get you less of the picture in focus (i.e. blurry backgrounds and potentially blurry portrait subjects), and bigger numerical values get more of the subjects in focus. And the closer you are to your subject, less will be in focus. So if you really wanted to shoot at f/1.4 and have two subjects in focus, move back.

For artistic value while taking candid family photos, I prefer Av mode myself. It's not daunting at all if you understand what effect aperture values have on your photos.

10-12-2012, 05:04 AM   #5
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For 2 people, you need to use something like f/4 or even further, but you will invariably loose much of the background defocus effect. Unfortunately you can't have it both ways. This is why studio portraits are done using a blurry backdrop, to artificially produce the dreamy effect while allowing your whole family to be in focus. Indoors, your options can become more limited due to less light. Sometimes, you just can't take candid portraits, and you have to tell your subjects to move, or you need to reposition yourself so that both subjects are equidistant from the camera. Keep experimenting and good luck.
10-12-2012, 05:13 AM   #6
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Hello Dr Meerkat,

I suggest this discussion about aperture (F numbers) and DOF https://www.pentaxforums.com/forums/pentax-beginners-corner-q/163961-question...pth-field.html There you can find out web addresses of DOF calculators.
F1.4 refers to extremely wide aperture. I think it is too wide for a standard portrait. The problem of indoor photo is related to poor lighting. The light conditions usually corresponds to exposure values 5-8 EV. So it means that you should use either wide aperture or slow shutter speed or high ISO. The wide aperture makes shallow DOF. The slow shutter speed can cause motion blur. The high ISO means risk of noise. So you should find out some trade-off. As know, Pentax K-r works quite well at high ISO. I presume you can use ISO 1600 or even ISO 3200 without noise. Such ISO values allows working with smaller aperture and faster shutter speed.
As you have 50 mm lens, it means you should use shutter speed 1/75 or faster (IS allows using slower shutter speed a little bit but it is better to use 1/75). In order to achieve exposure 8 EV at shutter speed 1/75 and ISO 1600, you can use aperture F8. Such an aperture provides quite large DOF. The width of DOF will be about 1.2 m if the distance to object is 3 m. If the distance is larger, the width of DOF will be larger, too. In order to achieve exposure 5 EV at shutter speed 1/75 and ISO 1600, you should use aperture F2.8. If the ISO is 3200, the aperture should be F4. The width of DOF will be 0.41 m and 0.59m respectively if the distance to abject is 3 m.
These calculations show that in-door photographing is challenging. You should try to increase DOF and provide good exposure at the same time.

Best regards,
Alberts
10-12-2012, 07:53 AM - 2 Likes   #7
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Focus is a function of distance.

If you want the two people in your shot to be in focus, and you want to shoot wide open, each person needs to be EXACTLY the same distance from the camera.

Stopping down gives you some margin for non-equal positioning. Stopping down a couple of stops will also improve sharpness.

Why don't you experiment a bit? Try some shots at f4 and study the results. If you're shooting available light indoors, you'll likely benefit from the use of a tripod to combat camera shake. Or crank up the ISO to 800 or so.
10-12-2012, 09:25 AM   #8
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QuoteOriginally posted by johnyates Quote
Focus is a function of distance.

If you want the two people in your shot to be in focus, and you want to shoot wide open, each person needs to be EXACTLY the same distance from the camera.

Stopping down gives you some margin for non-equal positioning. Stopping down a couple of stops will also improve sharpness.

Why don't you experiment a bit? Try some shots at f4 and study the results. If you're shooting available light indoors, you'll likely benefit from the use of a tripod to combat camera shake. Or crank up the ISO to 800 or so.
Excellent and very simple, practical advice. While f/1.4 can produce some nice portraits, the depth of field is very narrow and and it takes some practice and experimenting to get it to right. Sometimes, it just isn't going to work for the shot and stopping down a little is necessary.

10-12-2012, 10:41 AM   #9
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QuoteOriginally posted by reeftool Quote
Excellent and very simple, practical advice. While f/1.4 can produce some nice portraits, the depth of field is very narrow and and it takes some practice and experimenting to get it to right. Sometimes, it just isn't going to work for the shot and stopping down a little is necessary.
Tiere also is the artistic approach of deliberately having the second person out of focus. But for two people to be in focus, there is one thing to. Consider in addition. It may be best to have neither on the optical centreline, and to use an alternate focusing sensor. Most lenses have a curved not flat focus plane, something often ignored except with macro lenses which have a flat field. With a curved focus plane, two people side by side are NOT the same distance from the camera optically, if one is dead centre in the frame. Try setting the focus to either auto or select a side or corner focus point and place the other person in the opposite corner. If this is not practical, have the two people slightly staggered, but do not shoot them straight on. It is all about posing and framing the shot
10-12-2012, 11:18 AM   #10
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I was thinking "distance is the key" but johnyates beat me to that, so full credit there. Keep both faces at the same distance and they'll be covered by the same depth of field/aperture value. If you end up moving to some aperture like f4, try to get your subjects a little distance between themselves and a potentially distracting background. That background will then be out of the range of sharp focus.

When you switch from one of the Picture modes to the other side of the Mode dial (M, Av, Tv, Sv or P) you may have to make some other adjustments. The picture modes may apply some extra processing steps to the image, settings that Pentax thinks are pretty good for all portraits or moving objects or whatever . The manual mentions "a healthy and bright skin tone" for portrait mode, which is vague. My point is, you may notice photos taken in Portrait mode look slightly different than Av mode, even if all the same exposure settings are used. If you really like Pentax's choices, it would mean exploring the Image Finishing Tone options on page 213 of the manual, or using software to process the images on the computer, to reproduce the look. The camera doesn't do anything amazing that can't be replicated, so don't let it discourage you from the lettered modes.
10-13-2012, 07:11 AM   #11
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All good advice. I'll add one more tidbit.... A rough rule of thumb regarding depth of field is 1/3 is in front of the optimal focus point and 2/3 is behind the optimal focus point. If you HAVE to make a choice as to where to place your optimal focus point, chose the forward most eye(s). Also, to recover some of that dreamy background, whenever possible add more distance between your subjects and the background.
10-13-2012, 08:15 AM   #12
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There's a lot of good "technical" suggestions here, but I'll try to simplify it a bit.

With your 50mm mounted to your camera you shouldn't have to worry about getting too close to your subjects. The closer you get to the people you're shooting (nearing minimum focus distance), the more blur you'll see in your photo outside of the area in focus (narrower depth of field). Distance of a person from the background is important, but so is the distance of the camera from the person. That being said, and giving some room between you and the people you're photographing, here's a general rule I use:

2 people = f/2.8
3 people = f/3.5
4 people = f/4.5
5 people = f/5.6
and so on...

Make sense? It's easy to remember 2=2, 3=3, etc. This may not work in all situations, but it's a nice guideline when taking pictures of more than one person. Try it out and see if it helps. Set your camera to Av and match the aperture to the number of people.

Also, take a look here and move the sliders to get a better understanding of the effects of changing ISO, aperture and shutter speed: Aperture, shutter and ISO value | SLR Camera Simulator
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