Best portrait lens

Hi

I have a K100D, with an old manual 50mm f1.7, a Sigma 70-300 f4.5 and the kit lens and was wondering, what was the best portrait lens to use? I am thinking the 50mm as its more equivalent to 85mm and that its also a lot faster for a nicer DOF, but I really like the look of a telephoto lens for portraiture but not sure that the Sigma is up to the job, especially with the slower speed....

I am likely to be using the 50mm I guess, but I have a problem focusing it in the darker light most of my portraits will be taken in as I am useless at manual focusing without a split circle on the mirror! lol! Any tips on this? Or, is there a CHEAP alternative that might be worth considering for portraiture?

Any help and advice on this would be great. Thanks!

John

Although I don't use manual focus lenses often it is not necessary to use the the visual image in the viewfinder to focus; at least I assume the K100D is similar in operation to *istDS, K10D, K20D and K-7 which I have experience of.

With a manual focus only lens I leave the fucus switch on 'S' then when I point the camera at the object the focus point indicators (red dots superimposed on picture in viewfinder) appear - I chose the one I want to use then turn focus ring until focus confirmation is lit (i.e. the green hexagon).
If you use centre focusing but need to recompose then hold shutter half pressed while recomposing; or select the ability to take photos without focus confirm in the menus - usefull if you are doing a lot of manual focusing - to allow recompose without half holding the shutter release..

I used a 50mm f2 "standard" lens for a portrait shoot all day and only reverted to the 18-55 when we went into the (small) studio. The narrow depth of field is outstanding, almost too shallow at times as it's too easy to get, say, nose in focus and ears blurred.

You're right about manual focus it's demanding, but at least you get to choose the exact point of focus rather than the lens choosing for you. When you get used to it you may find it easier and preferable, who knows!

To be honest,anything longer than, say, 58mm is going to make for a very unweildy portrait lens, with even head and shoulders shots necessitating long subject to camera distances. I find there's a comfortable working distance with a model, not too close; not too far away. 50-55 is about perfect.

video light may help on two fronts...
easier to focus, and redeye reduction... most are relatively cheap, run on aa batteries and fit in a hotshoe...

All great information guys, thanks very much! I shall endeavour with the 50mm then and set the camera as suggested. See how that goes. And a video light does seem to be popular bit of advice too....I may have to invest in one.

So glad I don't have to buy another lens yet...lol! Cheers guys!

John

be careful that you don't have two different light source colours in there, though, as you'll have a nightmare trying to reduce the differences.

Bret

Yep, fair point Bret, I shall make sure I turn it off once focused....lol!



Cheers and good point well made! lol!

John

gels work too...

truth is, a typical video light is gonna be warmer than flash unless it says "Daylight balanced"
so if your using flash, the flash should be set to over power the video light and it won't matter.. if the video light is your main source or fill source then it shouldn't matter indoors under incandescent light.
actually helps to warm up an image shot outdoors in the shade or in overcast light...

so like flash you need to be aware of it's color, and how to work with/around it!

The 50 mm only has the field of view of a lens 1.5 times longer focal length. However, the cropped sensor sees no more magnification with a 50mm lens tahn a FF sensor.

Regards

This is all excellent info guys. Thank you so much. Glad I registered here now...

I have used a video light doing a second shoot at a wedding in the evening, but it was only used to light up the subjects when the focusing couldn't cope in the low light. The shot was taken with it off and the flashes took over....I wouldn't have actually thought to use it as a main light. But fair point, they are quite bright and realise they could be used. Will bare all this in mind...thanks again!

Sorry to go off topic here but is it not better to use angel of view instead of field of view?

If you want you can have the same field of view with a 50mm lens on an APS-C sensor compared to an MF.
FOV increase with distance so that's why you can have the same FOV.

Am I correct or do I mess it up now?

FOV is fixed per lens focal length as per image area coverage of sensor.

A 50mm lens is rated at approx 1x magnification on a FF sensor. On a croped sensor it is 1/1.5 or .666. The focal length of a lens on a SLR/DSLR body does not change, we just see less area or .666 of a FF image.

FOV doesn't change with distance. The angle is constant. Opposite distance "width" increases with distance.

The magnification of a 100mm lens is approx 2x on a FF sensor and remains so on a cropped sensor. Moving back 1.5 times the distance from camera to subject is the same image as a FF but is still .666 of the size.

Regards

I have an old 50mm f2.0 lens which is my preferred lens for portraits. I rarley use it at F2.0 but end to stop at around F2.4-2.8 where it seems to be better. I shoot in manual focus when my young daughter keep still long enough! and increase the ISO anywhere up to ISO800 to avoid using flash, this works for me as I've not mastered flash yet.

I've tried my 70mm macro sigma lens as this is also fast at F2.8, but I'm always moving away from the subject so tend to stick to the 50mm lens which is old but a cracker, try experimenting with changing the ISO, this has helped me improve my portraits.

Thanks Simon, I am more convinced I should stick with the 50mm and do as you said...but I like to use strobes as well, so the ISO isn't quite as important. Its just that its usually dark before they go off.....

BUt comments like yours convince me more. I shall hopefully post results on here. Thanks again!

J

No you got that wrong.
AOV (angle of view) has a fixed angle and is fixed per lens relative to the sensor size, look up a lens specification, it says AOV.

And yes FOV change with distance since it's in the formula:


f is the film distance (focal length can be used most of the times)
d is the object distance
o is the object dimension
i is the image dimension