[clackers]

. The only problem with that is, moving away from the subject creates additional distortion in the image that may or may not be desired. Is that all correct?

The opposite. It flattens, lacks distortion/drama.

Just aesthetics.

[normhead]

This is a function / behaviour that exists to some extent in all internally focused lenses , but zooms exhibit the greatest amount.

Sadly no lens review ever reports on this so users are left to figure it out by themselves

The DA 18-135 is not an internal focus lens, focus breathing is not an issue.

[Cambo]

All of my paid portraits were done with the FA77, from the K10D forward. The DA70 would make a great portrait lens also.

I think you have a good understanding of the “crop” factor. So yes, anything from 50 to 135 will work. While I loved using 135mm lenses on film (and again with the K1), they just put me too far from the subject with an aps-c body. I also prefer the 40, 43, 50 for portraits that are half to 3/4 body shots. YMMV

I’ll vouch for the 40mm f2.8: wonderful portrait lens.

[Lowell Goudge]

The DA 18-135 is not an internal focus lens, focus breathing is not an issue.

While not internally focused, it still may exhibit focus breathing. This is also a complaint on other zooms that exceed a 3:1 zoom ratio most notibly are the 18-200ish zooms

This is done to minimize the difference between minimum and maximum lense overall length and make lens mechanics simpler.

[Docrwm]

The 70mm is like the old 105 from film days. Some of the best portrait photographers took some of their most flattering photos with 105s. Its a nice lens and is 2nd only to my 85 for the beauty of the portraits that I can capture with it.

[photoptimist]

So, I think this is what I was thinking originally but I want to make sure I understand. It seems like the conversion from FF to APSC has to do with multiple things. The main difference is image size on the sensor for the same picture. Meaning, the smaller APSC will capture a smaller portion of what comes through the lens. In order to stand in the same spot and achieve the same sized image on the sensor, you would need a lens with a wider field of view. 1.5 times wider to be exact. If you wanted to use the same lens on APSC as on FF for it's distortion properties, you would have to move further away from the subject. The only problem with that is, moving away from the subject creates additional distortion in the image that may or may not be desired. Is that all correct?

Basically, what I'm getting from this is; stop trying to figure out which lens is "best" and figure out what I want to accomplish within the photo. Then use the lens and distance that best captures what I'm looking for. Is that right? Like I said earlier, right now, I've got an A 50mm 2.0 and a 100mm 2.8 Macro. It seems like these may be fine for certain portraits I'm looking for but not for others. Would you all say adding a DA 70 (because there's no way I can afford the FA 77) would kind of round things out for me? It will certainly be some time before I can pick it up (months to years) but I like knowing where I'm going so I can plan for it. In the mean time, I can also use my 18-135mm for anything needed between the two primes. The DA 50 1.8 might be in the future as well but it will depend on how the manual focus of the 50 2.0 goes. I know it's not a highly regarded lens but, for me, I think it will do fine.

Thanks for all the feedback. I love nerding out on a lot of this stuff. It definitely helps me to understand how it all works.

That sounds about right.

The only issue is that when you say "distortion," you might be talking about two different issues. Some lenses do have an intrinsic distortion. They distort straight lines into curved lines. That makes buildings, windows, and other rectangular objects look like inflated barrels or pinched-in pin-cushions. That type of distortion is a property of the lens that independent of the sensor format (although barrel or pincushion distortion is less obvious on a crop sensor). Note that some zooms have barrel distortion at the wide end and pin cushion at the long end.

But if you are talking about "distortion" of facial features from using different lenses, then that is only a matter of lens-to-subject distance, not focal length. Stand 10 feet from the person and photograph them with an ultrawide angle lens and you'll find that their face in the center of the picture does not show any "wide angle" distortion. Stand 1 foot from a person's nose and photograph them with a 200 mm telephoto and their nose will become a bulbous protuberance in front of an overly-rounded head.

Thus, you want to first set the distance to the subject to set the look of the shape of the face and then pick a focal length that creates the width/height of frame width you want around the face/torso/body.

[Navmaxlp]

That sounds about right.

The only issue is that when you say "distortion," you might be talking about two different issues. Some lenses do have an intrinsic distortion. They distort straight lines into curved lines. That makes buildings, windows, and other rectangular objects look like inflated barrels or pinched-in pin-cushions. That type of distortion is a property of the lens that independent of the sensor format (although barrel or pincushion distortion is less obvious on a crop sensor). Note that some zooms have barrel distortion at the wide end and pin cushion at the long end.

But if you are talking about "distortion" of facial features from using different lenses, then that is only a matter of lens-to-subject distance, not focal length. Stand 10 feet from the person and photograph them with an ultrawide angle lens and you'll find that their face in the center of the picture does not show any "wide angle" distortion. Stand 1 foot from a person's nose and photograph them with a 200 mm telephoto and their nose will become a bulbous protuberance in front of an overly-rounded head.

Thus, you want to first set the distance to the subject to set the look of the shape of the face and then pick a focal length that creates the width/height of frame width you want around the face/torso/body.

Ok. This is makes sense to me. There is lens distortion (or lens characteristics if you prefer) and there is distortion based on distance from the subject and both should be used to capture the desired image. Correct?

Wow, photography continues to become more and more involved and exciting the more I learn.

[Just1MoreDave]

The DA 18-135 is not an internal focus lens, focus breathing is not an issue.

[pres589]

I still don't think focus breathing is going to be an issue if you're using a "standard zoom" to try and figure out what focal length you enjoy shooting portraits at. It's a very general idea as mentioned previous with no one perfect focal length for all portraits. So if a bit of focus breathing throws things off, so be it, as every shot is a little different (this assumes you aren't doing this in a very controlled environment that is set up the exact same every time, and even then...)

The original poster has a crop body, a 50mm prime, and a 100mm prime. While I wouldn't regard either of the specific lenses he has as optimal examples of a 50 or 100 for this purpose, they're good enough. Shoot around with both and see what makes sense; stay around 50mm, stay around 100, go about perfectly in-between, etc. Price already has driven him out of buying an FA 77 per his own comments here, so really it's considering a better 50, maybe the DA 70, maybe a better zoom like the Tamron 28-75, etc etc.

[AlwaysAl]

Having experienced a similar dilemma with portrait lenses, here's my path of discovery; Started with a 28-75 Tamron zoom and was initially attracted to the DA*55 for all of its qualities (bokeh, etc). In practice soon discovered that "portrait" for the functionality of my interests basically meant "head shoulders, waist up" and this lens proved beautiful. My preference though was to shoot more full-length shots and found the DA*55 left me feeling disconnected from my subject due to the distance. Someplace around that time, discovered in PhotoShop the available summary of shots and the focal length used and found I actually was shooting (with the Tamron) more in the 28-35 zone. Started a pursuit for the next answer and settled on the Sigma ART 18-35. This, for some time, became my go-to lens...loved everything about it. Moving to the K-1 found I wasn't comfortable with either the DA*55 or the Sigma on this body...been experimenting with a Sigma 70-200 and have recently acquired a FF 50mm that holds promise,..haven't quite got that comfort level back yet.

[pres589]

Having experienced a similar dilemma with portrait lenses, here's my path of discovery; Started with a 28-75 Tamron zoom and was initially attracted to the DA*55 for all of its qualities (bokeh, etc). In practice soon discovered that "portrait" for the functionality of my interests basically meant "head shoulders, waist up" and this lens proved beautiful. My preference though was to shoot more full-length shots and found the DA*55 left me feeling disconnected from my subject due to the distance. Someplace around that time, discovered in PhotoShop the available summary of shots and the focal length used and found I actually was shooting (with the Tamron) more in the 28-35 zone. Started a pursuit for the next answer and settled on the Sigma ART 18-35. This, for some time, became my go-to lens...loved everything about it. Moving to the K-1 found I wasn't comfortable with either the DA*55 or the Sigma on this body...been experimenting with a Sigma 70-200 and have recently acquired a FF 50mm that holds promise,..haven't quite got that comfort level back yet.

Hey Always, have you tried going back to that Tamron 28-75 for this purpose?

[mcgregni]

When we say a lens on APSC is 1.5 times the focal length

And that's what we shouldn't say, as it leads to misunderstanding.

[normhead]

Oh ya, it's an external zoom but internal focus. It still doesn't particularly focus breathe.

[AlwaysAl]

Hey Always, have you tried going back to that Tamron 28-75 for this purpose?

Thanks for your comment and, yes I have. To be honest, in its day, thought the Tamron was "it" with its 2.8 aperture through the range and shamed the Sigmas I had. Unfortunately, today, when you put it on the K-1, you can feel/see the technology gap. It's still sometimes fun to use it but, we've seemingly fallen out of love when these new lenses (like the D FA*50) are so seductive. Trying to learn to "zoom with my feet" more and that's probably my biggest challenge (why walk when you can zoom?). Now you've stirred these memories, I think I'll go home this evening and take out the Tamron, express my sincerest appreciation for the help it gave me along my path and once again restore it to its storage spot while I deal with my guilt. lol

[pres589]

Always: The reason I asked is that it covers a focal length range that seems pretty close to what you had with the 18-35 Sigma with more reach tacked on beyond the 35 max of the Sigma.

I think if I was trying to do portrait work for money, with my crop K-5 II, I would buy the Tamron 28-75 and pair it with a decent fast 50. For a few years there was an autofocusing Tamron 90mm f2.5 macro that might be worth looking at as well.