[SOldBear]

I use either FA50 or DA70 for portraits. The DFA 100 WR is great, but in most cases I don't have the space.

I had an A*85 F/1.4, but found it too long for portrait, so I sold it.

Let me answer the OP's question in a different way: a 35mm camera + 85mm lens has the same FOV (and the same perspective distortion) as an ASP-C camera + 55mm lens. In other words, if I put the (35mm camera + 85mm lens) and the (ASP-C camera + 55mm lens) at the same position, the image they record will be the same.

[audiobomber]

Really? What about other Pentax 50mm lenses?

I have no idea. I only know about the FA 50mm f1.4, because I've seen it mentioned in a couple of reviews, for example this one at Photodo:

MTF Data
Effective focal length 52mm
Pentax SMC-FA 50mm f/1.4

[Ikarus]

if I put the (35mm camera + 85mm lens) and the (ASP-C camera + 55mm lens) at the same position, the image they record will be the same.

In terms of perspective, yes, but not in terms of depth of field, unless the f stop scales with a factor of 1.5 as well. The good thing about 50s being the 85mm equivalent on APS-C is that there are many fast lenses readily available that fit the bill. A 85mm at f/2.8 on full-frame is nicely approximated by a Super-Tak 55mm at f/1.8 on APS-C.

[tuco]

I'd say the way to get great bokeh is to have a lens that is good at it. If your lens is not known for great bokeh ( smooth, creamy, etc), more OOF probably doesn't improve the situation.

[Venturi]

Perspective distortion is the key element when considering focal lengths and capture formats. The smaller the format, the shorter the focal length you need to capture the same field of view from a constant distance, and the more perspective distortion that will result.

As they say, a picture says 1000 words.

Perspective distortion (photography) - Wikipedia, the free encyclopedia

[Cannikin]

Perspective distortion is the key element when considering focal lengths and capture formats. The smaller the format, the shorter the focal length you need to capture the same field of view from a constant distance, and the more perspective distortion that will result.

Focal length has no (direct) relation to perspective. Perspective is a function of camera position only, nothing else. Go ahead, try it right now. Take a shot with a 100mm lens, then from the exact same spot take another shot with a 50mm lens and do a 2x crop. Guess what happens to the perspective (answer: absolutely nothing).

Perspective can be summed up very simply:
- Subject A and B are exactly the same size
- A is at distance 1x, B is at distance 2x
- A will look twice the size of B (2x/1x)

That's it, no focal length, crop factor, or even a camera. Just an observer and a distance. "Perspective distortion" (in this context) is simply some features being closer to the camera (like the nose) than others (like the eyes and ears), making them look relatively bigger.

The whole discussion of "perspective distortion" in portrait lenses breaks down to the following questions:
- What distance does the ratio of feature sizes look good to you?
- With what lens will the subject be framed the way you want on your camera at that distance?

As you can see, "crop factor"/"equivalent focal length" matters in that second question. True focal length is ultimately irrelevant (besides DOF).

[Lowell Goudge]

Cannikon I think what Venturi means is that when you move closer to the subject, to get the same subject size when you change focal length, it increases the perspective distortion.

I agree with you, if you remain in the same place, and change only focal length, perspective does not change, and you can see this by shooting say, a 100 mm and a 24 mm from the same spot, and then cropping in on theb24mm shot to show the same image, the perspective of the two images will be the same.

[Ratmagiclady]

(Just to chime in a bit, I would not be concerned about the difference between 50 and 55mm for practical purposes on modern digital cameras if it's the close end of working distance you're worried about: you can pretty easily use the same working distance without worrying about squeezing out every last bit of sensor area, I think. I'm very fond of my FA 50 for the same reasons I love my 85 on my film cameras, and I use the digital somewhat more casually, the bit of extra FOV is as often handy as not. I only really ever miss the bit of difference if I'm doing other things than closer-in people shots, really.

[magkelly]

I work almost exclusively in portraiture and I often do it in a very tight space. For me a lens longer than 135mm can be very impractical. When it comes to primes I do tend to use lenses in the 50-100mm range a lot because they are more affordable for me than ones in the 85mm range. I don't think the 15mm makes all that much difference though. A 100mm lens really works about the same for me as an 85mm. Going up to 135mm can change things and going down to 50-55mm does but in the end it's all about how much space I have to work in and what the image looks like when I am taking the pic. I go by that much more than which lens mm is supposed to work best for what.

Can I get everything I want in the shot? No? Why not? Is the lens actually too long or do I just need to step back and re-frame my shot a bit better? Most of the time the answer is just that. I need to readjust where I am standing not the lens. So many photographers it's like they just don't want to move at all these days. They'd rather change to a longer or shorter lens than move back or forward a foot. But I find that's just not always the answer changing lenses. Often that foot one way or the other it's perfect. I just have to move me, move the subject, and it's fine.

I seldom change lenses more than maybe once during a shoot actually. Once I get which lens fits the space I am in that's it, and usually the first one does because I'm getting so used to working in a tight space I automatically grab the right lens for the job the first time. Usually it's one of my 100mm's but I keep a 55 handy too, just in case I want it. You don't really need expensive 85mm lenses to do portraiture. Sure I'd love one, but I can live without if I am willing to get a little sweaty and move position once in a while and that's all it really takes.

I'm not fond of anything below say a 45mm for portraiture. I don't like a wide angle for portraits. I think it can be very unflattering. But a 50mm-150mm, anything in that range on either type of camera can work just fine for me. I seldom use a longer prime lens though unless I'm doing portraits of animals and not people and can't get close. I have used my 75-200 or 75-300 zooms but I'm definitely at the low end of the zoom, not the high end doing that unless I'm standing way back trying to fit a whole group of people into a shot. Any lens almost in the range of 45-200 can and will take a portrait shot. You just have to move yourself to get the sweet spot sometimes.

FYI, I do go to clients homes depending upon the situation. Occasionally I will shoot on location or rent a local studio space. But most of the time I have my clients sitting in my screen room with about 4-5 feet of shooting space, max. Sometimes it's even less than that. I've even been known to put the backdrop up out on our driveway under the cover there and string up sheets across the end of the drive for privacy on nice days. (Keeps the nosy neighbors guessing...) Whatever works. If there is one thing I've learned in life that really applies well to being a photographer it's that I have to be able to adapt to just about anything if I want to get the job done. By nature I'm ultra prepared but if I don't have something right at hand? I MacGyver it or simply adapt the situation to where I can do what I need to do without. You really do have to be flexible as a photographer, learn to think outside the box.

[stevebrot]

Focal length has no (direct) relation to perspective. Perspective is a function of camera position only, nothing else.

Finally, the right answer.

• Perspective is a very important element in composition, particularly portraiture
• Camera position (actually position of the front lens element) determines perspective. Sort of like how where you are standing determines what you see (duh!). That is why zooms are so attractive.
• A moderately long focal length (say 50-85mm for APS-C) allows for a working distance that gives a pleasing portrait perspective

It is as simple as that.

The cool part is that 50mm works great for portraiture on APS-C and that fast aperture lenses at that (and similar) focal length are incredibly common at very reasonable prices.

Edit: Forgot to mention that baro-nite's initial response to the OP would probably have been an adequate final response. Thank you, baro-nite for reminding me (see post below)

Steve

[baro-nite]

This whole. Discussion is a lot of BS (sorry for the strong language).

Finally, the right answer.

I'm all for calling out wrong answers, but this seems pretty strong given the number of right answers already in this thread.

[stevebrot]

I'm all for calling out wrong answers, but this seems pretty strong given the number of right answers already in this thread.

Sorry baro-nite. I intended to credit you for leading the OP in the right direction on the first reply. A lot of what followed, however, was a bit off-base, even if true.


Steve

[Tanzer]

The statements regarding distance being the only factor affecting perspective distortion are absolutely correct. As we all keep saying over and over again.

But just to be clear, no one here is actually suggesting to go take portraits with a 15 mm lens on the OP's APS-C camera from 5 meters away, and crop 20x for best results. (But putting a 15 mm on the Q, that is a different story.)

[HSV]

The cool part is that 50mm works great for portraiture on APS-C and that fast aperture lenses at that (and similar) focal length are incredibly common at very reasonable prices.

Steve

Thanks god for the crop factor...carrying a 50-135 as a default portrait zoom is a lot more comfortable than a 80-200.

One strange thing I've always though, we know that the DA limiteds each have own sort of default application (15/21 as wide angles, 35/40 as normal every day lenses, 70 for portraits). Now, why would Pentax not have any more DA limited on the shorter end of the portrait focal lengths for APS-C?

Pentax is well known for those weird focal lengths (like 21, 31, 43, 77)..in my though, they would have made some DA limited with some weird focal length between 50 and 70 for use in portraits with APS-C.

Back to the original topic, one thing to take into consideration, as Lowell pointed out, is to chose the focal length depending on space and composition instead of blindly following a rule of what focal length are considered portrait or not. For me, I find that my most used focal lengths for portraits (when shooting primes) is 40-50mm. In most indoor situations, the 70mm is just too long for anything more than a head shot (at least, for me) and most of my people shots are half body.

[Tanzer]

One strange thing I've always though, we know that the DA limiteds each have own sort of default application (15/21 as wide angles, 35/40 as normal every day lenses, 70 for portraits). Now, why would Pentax not have any more DA limited on the shorter end of the portrait focal lengths for APS-C?

Pentax is well known for those weird focal lengths (like 21, 31, 43, 77)..in my though, they would have made some DA limited with some weird focal length between 50 and 70 for use in portraits with APS-C.

The DA Ltds are primarily intended to be small and compact, whereas a portrait lens usually is built around a large aperture to give the option of very shallow DOF. Hence the DA*55 f/1.4. (I usually stop mine down to f2.0 to 2.8, otherwise the DOF can be too shallow.)