Using a tele converter for portraits?

[peter2022]

I know that lenses 80mm and longer (in 135 terms) are favored for portraits since they smoothen irregular facial features by somehow “flattening faces” but…what happens with a tele converter?

Say I put a 2x teleconverter on a 50mm f/1.2@1.2, thereby having an effective focal length of 100mm.

I am drawn to think:

1 the image is just magnified, so I don’t get the “flattened perspective” of a longer lens
2 out-of focus areas stay the same because I’m still @1.2
3 I need a film four times the iso because I am losing two stops (so 400 iso instead of 100 iso for example)

So facts 1 and 3 suggest that I still need a 100mm lens , maybe less so for landscapes.

Am I correct?

 

[AgX]

Interesting issue you put up.


The "flattened perspective" (same as the "big nose" in short FL portraiture) is just a matter of camera-subject distance and other details' distance ratio to this.
It does not matter how the effective focal length is achieved. With the 50mm-converter combo you have to stay off same distance from your subject as with 100mm lens when obtaining same image scale.

 

[jeffreyg]

Using a 2x extender (3) you have to increase the exposure by the equivalent of 2 stops but you can keep the same ISO film just adjust the time. ie f1.2 @ 1/250 to f1.2 @ 1/60

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[AgX]

Concerning DOF:

That the new DOF has to be calculated based on the new effective FL is likely out of question.

The issue though is whether it is to be calculated on the primary aperture, or the new effective aperture. (In your case 100mm/1.2 or 100mm/2.5.) And here typically discussion starts...

 

[peter2022]

Thanks for the excellent contributions- why are not teleconverters a thing for portraits then?

 

[AgX]

At least in the longer past a typical camera bag included a 50mm 1.4 and a 135mm 2.8 lens.

For this case using a 2x converter resulting in a 100mm 4.0 lens makes not that much sense.


Another aspect though may be interesting for subject details: the 135mm lens typically has a min. focusing distance of 1.5m, the 100mm by extender lens only 0.5m.

 

[Bronson Dugnutt]

Thanks for the excellent contributions- why are not teleconverters a thing for portraits then?

Personally, I would opt for a 85/105/135mm prime before I'd ever think of teleconverting a shorter lens, but I have had fun experimenting with teleside converters and shorter lenses. With this style of converter you'd don't lose any light as long as the converter's rear diameter is the same or larger than your lens's front filter.

 

[lxdude]

I used a 2X teleconverter on a 55mm f/1.8 lens long ago when that was all I had. It was a cheap one, and quite good for portraits because the results were rather soft, which gave a nice effect without much loss of contrast.

 

[AgX]

I have had fun experimenting with teleside converters and shorter lenses. With this style of converter you'd don't lose any light as long as the converter's rear diameter is the same or larger than your lens's front filter.

Front attachments are yet another thing. Aside of close-up lenses, hardly ever discussed at this forum.
As they do not reduce aperture a good idea to hint at them.

 

[MattKing]

At least in the longer past a typical camera bag included a 50mm 1.4 and a 135mm 2.8 lens.

For this case using a 2x converter resulting in a 100mm 4.0 lens makes not that much sense.

Actually, the result would be a 100mm f/2.8 lens, which is quite usable.
There are three advantages to teleconverters:
1) cost, vs. the cost of another lens;
2) size and weight, vs. the size and weight of another lens; and
3) close focusing capability.
With number 3), the lens plus teleconverter has the same close focusing ability as the lens alone, but of course the image is magnified, so the result with respect to the size of the subject in the frame is similar to being able to move in closer.
For portrait work, the tele-converter allows you to still fill the frame while moving farther from the subject. The change in perspective that results from moving farther away is flattering to many portrait subjects.
The main dis-advantage to teleconverters is that you reduce contrast, resolution and apparent sharpness, due to the fact you are magnifying the image presented by the lens.
A good quality teleconverter can still give really good results - just not the same "pixel peeping" numbers.
And just for the fun of it, this is an RB67 with 180mm lens and 2x teleconverter:

 

[Donald Qualls]

And just for the fun of it, this is an RB67 with 180mm lens and 2x teleconverter:

Unfortunately, that's now an f/8 (ish) lens. Better have some lights. I've got that combination, though I haven't shot the 180 yet either with or without the converter. I have shot my 250 mm with the converter; kind of disappointing (but I'm not likely to save up for a couple years to get either a 360 or 500, so on the rare occasion I need a lens longer than 250, the 180 or 250 gets the converter).

 

[AgX]

Actually, the result would be a 100mm f/2.8 lens, which is quite usable.

Yes, of course. Likely it was a Freudian slip to prove even more that adding a converter just for tat set makes not that much sense.

But taking for portraiture the converter instead of the 135 might be considered, to safe weight and to reduce min. focusing distance.
Or adding it to the 135mm lens


Taking only a 50mm and a 2x converter thus makes sense. But as the OP indicated, this is hardly talked about.

 

[btaylor]

Yes, the reduction in image quality might be just the thing you want, and the f2.8 stop will throw the background nicely out of focus if that’s what you’re after. Even though I’ve gotten a few of the cheap teleconverters I’ve never used them because I would just use a 85/100/135 prime and because I don’t own any super fast (f1.2) 50’s anyway.
It interesting that the front mounted (teleside? never heard that term before) is so rarely mentioned. I have a high end fixed zoom Canon Super 8 camera, and there were high quality front mounted tele, wide and close up lenses available for it. I screwed the close up adapter into a 400mm Spiratone (remember them?) tele on my OM1 for some macro shots of our bee colonies decades ago and the results were impressive.

 

[peter2022]

The main dis-advantage to teleconverters is that you reduce contrast, resolution and apparent sharpness, due to the fact you are magnifying the image presented by the lens.
A good quality teleconverter can still give really good results - just not the same "pixel peeping" numbers.

I understand now! My specific combination would be a Rollei Xenotar 80mm 2.8 on a 2x HFT teleconverter…I’ll have to test the combination then to see whether the result is acceptable.

 

[AgX]

"HFT" already indicates that it is a converter designed for high image quality.