Crop factor question

Apologies for a noobish question but trying to learn.

I have a 40d and am looking for a good quality prime for portraits. I've watched a few of the digital rev videos on YouTube as they are pretty funny. They have a few '5 reasons why you need a xxmm lens" and I noticed on the 85mm video the chap said it was good for portraits - amongst other things.

Now he was using a 5d iii (which I would love but unfortunately can't justify). If I have an 85mm lens on my crop sensor body I will get the equivalent of ~135mm so not the 'same' lens?

I have a 60mm macro lens which I suppose is close-ish to ending up at 85mm so I should find it good for portraits, it isn't bad but I'm not sure whether is 'distorts' features or not.

I took this last night

For studio-like appearance (in terms of perspective effects), lenses with equivalent FL 85..135mm are the ones to get/use. Meaning on your crop camera it'd have to be 50..85mm lens. Much less than that, and faces will look very funny (exaggerated perspective - nose too large etc.). Much more than that, and faces might appear too flat (almost like drawn on a paper).

If you want to make an environmental portrait (where a significant fraction of the photo is occupied by the environment, which is typically used to suggest what that person is doing for living or as a hobby), then you'll need a shorter FL - probably between 35 and 85mm equivalent (22-50mm on crop). Some perspective distortions (at the shorter FL end) are acceptable in environmental portraits.

You already have 24-105mm, so you are all covered in terms of portrait FL range. The other parameter would be how much you want your background to be blurred. In studio setting, it is not usually needed - most studio portraits are shot at f/5.6...f/11. For an outdoor portrait with very busy background, something like 85mm f1.8 should do much better job than your 24-105 in terms of blurring the background. If you are willing to spend more, you could get even better outdoor portrait lenses, like Sigma 85mm f1.4, 85L, or 135L (the latter would force you to stay pretty far from the model, but it is an amazing lens otherwise).

If someone says that they use an 85mm lens on a so-called "full-frame" camera such as the 5D series, you can get the same field (angle) of view by using a 53mm lens on your 40D. That's 85mm divided by 1.6. Anything from 50 to 60mm should do fine, depending on your working space.

The real key, when doing portraits, is to keep enough distance between the camera and subject to prevent perspective distortion (relative size of nose vs ear, for example) and use a focal length that allows you to frame the image the way you want to.

For more information on perspective control, please read our "sticky" (found in the General Photography Talk forum) tutorial titled Perspective Control in Images - Focal Length or Distance?.

Thank you both.

So the 85 (or even 135) would be ok on my camera? I would just need to be further apart.

I've also seen the 70-200 purported to be a decent lens for portraits. Although there's no way I could justify the f/2.8 version, it would probably be the f/4 non-is - which almost seems like a waste.

I'm in two minds about upgrading my body also, I'm attached to my 40d but it is terrible at any ISO above 640. Would love a 6d, but 7d is more likely.

Basically I have maybe £400 to spend. I don't need a full frame camera do I?

I like taking pictures of most things, but I want to be better at portraits (both location and studio), babies and kids.

Any opinions welcome!

It is not focal length that causes distortion, it is your distance to the subject. That is why a 35mm might distort on full frame but not on a crop. I tried an 85 on a crop before and found it to be too long. For a crop, I prefer a 50mm lens. I would just pick up a nifty fifty if you wanted something faster than your 60mm.

Portraiture is very broad, you can use any focal length depending on the style you want to achieve. The above photo is a head and shoulders shot, again you can use many focal lengths, but usually longer is more suitable. If you can't tell if its distorted, then I don't see an issue.

The reasons I would use a 85 instead of 60 would not be distortion related, it would be more to do with lens quality, DOF, distance between camera and subject, the environment I was using it in etc

Ratjack wrote in post #16270692
It is not focal length that causes distortion, it is your distance to the subject. That is why a 35mm might distort on full frame but not on a crop. I tried an 85 on a crop before and found it to be too long. For a crop, I prefer a 50mm lens. I would just pick up a nifty fifty if you wanted something faster than your 60mm.

I don't think I necessarily need faster. Although I suppose the fact I'm using a higher ISO means I probably do...

I've had experience with two of the 50mm 1.8s and was most unimpressed with both - which is why I went for the 60mm which I have been pleased with.

I found with the 50mm at 1.8 is was soft (understandable) but stopped down maybe 1 the DoF was so narrow it would never be properly in focus how/where I wanted it to be. I suppose I need to be further away and then crop?

I think it's obviously the bit that's behind the camera that's causing it but I don't really understand how something like this can be taken at f/4 http://digital-photography-school.com …2013/09/Firass_​seated.jpg

But when I take shots at f/8 I end up with bits out of focus (eyes in focus for example but not nose or ears)

not until you learn to use your 24-105. Set the zoom at 85mm and use it for a day, that's pretty much how the 85mm focal length looks like.

Charlie wrote in post #16270740
not until you learn to use your 24-105. Set the zoom at 85mm and use it for a day, that's pretty much how the 85mm focal length looks like.

Do you mean I can't use it because my pics are bad?

When people say "85mm (on FF) is a great focal length for portraits" they are generally thinking of portraits that are much more loosely framed that the example shot you posted of your daughter. That example shot (while still being a portrait) would generally be referred to as a head and shoulders type of shot.

The basic idea for formal, posed portrait work is to keep the photographer far enough back fron the subject so that they don't start looking distorted. In some sense, you can't be too far back, but if you use really long lenses you might find the distance you need to be from the subject is inconvenient.

So really, anything from 50mm to 200mm is going to cover the heart of the range for portrait work on a FF camera. 50mm might be used for a really loose framed shot of an entire person with room around them while 200mm would be ideal for a head and shoulders shot such as you posted.

This range also explains why 70-200 zoom lenses are a very common range offered by nearly all SLR camera makers, as the range is very useful for portraits and event type work along with some other things.

On your 1.6X format camera, 35mm to 135mm covers the kind of range you need for portraits. If you want to shoot as tight as the example shot then try to use a lens in the range of 100mm to 135mm. One other note, you do not need a really fast (and expensive) lens for tightly framed portraits. The DOF with even a moderately slow lens like the 24-105L is going to be thin if you shoot a tight head and shoulders shot. I often will use apertures like f/8- f/11 if the shot is that tight, and the background will still be totally blurred.

Again, thanks.

I suppose I'm falling in the trap of thinking a new lens or body will magically make my photos better. I'll keep practicing with what I've got and try to improve technique.

sancho1983 wrote in post #16272273
Again, thanks.

I suppose I'm falling in the trap of thinking a new lens or body will magically make my photos better. I'll keep practicing with what I've got and try to improve technique.

There is no question that some lenses preform a lot better than others.
A great portrait is the result of
- Skilled photographer
- good light and use of
- Best equipment

A skilled model, or photogenic type person can also make a huge difference

The skill, and use of light is our learning curve. However the equipment is a limiting factor

I guess its a bit like using a saw. A jigsaw can cut a square board for you, and some will cut with it straighter than others, but a circular table saw is going to make the job easier and more accurate, but unless you know how to use either saw, your results are not going to be so good.

sancho1983 wrote in post #16270691
Thank you both.

So the 85 (or even 135) would be ok on my camera? I would just need to be further apart.

I've also seen the 70-200 purported to be a decent lens for portraits. Although there's no way I could justify the f/2.8 version, it would probably be the f/4 non-is - which almost seems like a waste.

I'm in two minds about upgrading my body also, I'm attached to my 40d but it is terrible at any ISO above 640. Would love a 6d, but 7d is more likely.

Basically I have maybe £400 to spend. I don't need a full frame camera do I?

I like taking pictures of most things, but I want to be better at portraits (both location and studio), babies and kids.

Any opinions welcome!

If your 40D is terrible at 640, then either 1 of 3 things are happening:
1) Your camera is defective
2) You are underexposing your shots and pulling them up digitally afterwards, try using the histogram and keeping it just right of center
3) You are not using the right software tools and/or techniques for post processing the photo

If you can provide some examples, we can point you in the right direction for this particular aspect of the 40D. It could really change your mind on what you need to do next.

Thanks.

Here's a picture I have just taken for test purposes.

Pretty much the same again.

Shot (excuse the mess):