Best Studio Lens for Full Body shots?

[jamesbjenkins]

If it was opinion-based I could understand 'disagreement', but it isn't. I'd love to hear any rational argument, or see any evidence, that supports the notion that lens focal length and not distance to subject affects this type of distortion. Take two images from the same postion, one with a 200 mm lens and one with a 28 mm lens (for example) and overlay them after changing the magnification. Apart from any pincushion/barrel distortion caused by lens defects (which are a feature of the particular lens design, not of all lenses of that focal length) they will be identical.

Take an hour or two researching the basic physics of light and photographic technology then come back here and correct yourself. Any fool with two eyes can look at a picture, not perceive distortion and then claim there is none unilaterally. Again, just because you can't see distortion in a particular image doesn't mean it doesn't exist.

Perspective distortion caused by a combination of subject distance and focal length will always affect the image, regardless of whether those differences are small enough to be imperceptible.

For instance, my 14-24 will ALWAYS distort a room I'm shooting, regardless of how close I am to the walls. The differences between a 50mm and a 85mm are much les noticeable unless you're too close to your subject, but they're most definitely there. You can't fool physics.

 

[Helen B]

Take an hour or two researching the basic physics of light and photographic technology then come back here and correct yourself.
...

Perspective distortion caused by a combination of subject distance and focal length will always affect the image, regardless of whether those differences are small enough to be imperceptible.

...
You can't fool physics.

I've spent rather more than two hours researching the basic physics of light and photographic technology. Please enlighten me and explain the physics behind what you are claiming, or point me to a website. Thanks.

Edit: Perhaps I should add my version of the physics.
Situation:
Two lenses of different focal lengths (flA and flB) with their entrance pupils in the same position relative to the subject.
Distance between entrance pupil and front nodal point small with respect to all other distances.

Consider:
Relative magnification of two zones of the subject, at different distances (ie how big things appear relatively, depending on how far they are away). Let's say the tip of the nose is at So1 and the ears are at So2.
Image distance for lens with flA is SiA, image distance for lens with flB is SiB.

Relative magnification of nose with respect to ears, lens A:
SiA/So1 / (SiA/So2) ie the magnification of the nose divided by the magnification of the ears
=So2/So1

Relative magnification of nose with respect to ears, lens B:
SiB/So1 / (SiB/So2)
=So2/So1

As you can see, the image distance cancels out. Only the subject distance is important.

 

[Robin Usagani]

You lost me HelenB. What is the difference between So1 and SiA ? I am trying to follow your explanation. What is So1 and So2?

My understanding is that your FOV is similar between 35mm lens on crop vs 50mm on FF when you are focused on infinity. But once you come closer to portrait distance, the difference is quite noticeable and the FOV of the 35 on crop will be wider. If the FOV is wider then the angle of FOV is wider. That means something farther from the focusing point will get smaller a lot quicker. So if you are focusing on the nose, then the ears will be smaller on the 35+crop. Isnt this what we are talking about? Best studio lens? We probably want to fill the subject in most of the frame?

 

[Helen B]

You lost me HelenB. What is the difference between So1 and SiA ?

So1 is an object distance (in this case to the tip of the nose) and SiA is the image distance for lens A. (Object distances are measured from the front nodal point to the object; image distances are measured from the rear nodal point to the image.)

I am trying to follow your explanation. What is So1 and So2?

They are object distances, 1 to the tip of the nose, 2 to the some point on the ears. The lenses are the same distance from the objects, so the object distances for lenses A and B are the same - we are trying to show the effect on perspective of focal length itself, not of distance, so the object distances are the same.

My understanding is that your FOV is similar between 35mm lens on crop vs 50mm on FF when you are focused on infinity. But once you come closer to portrait distance, the difference is quite noticeable and the FOV of the 35 on crop will be wider.

True. Let's quantify an example.

Suppose the 35 mm lens has exactly the same diagonal FOV at infinity focus as a 50 mm lens on 24x36. That would be 46° 48' (all values to the nearest minute).

Now focus to 1 m instead of infinity. The FOV of the 50 mm on FF is now 44° 41' and the FOV of the 35 mm on crop is 45° 19'. A difference of 38', or a shade over half a degree. Not a lot, but not zero either.

That means something farther from the focusing point will get smaller a lot quicker. So if you are focusing on the nose, then the ears will be smaller on the 35+crop. Isnt this what we are talking about?

Yes, slightly smaller - but the nose will also be slightly smaller, and the nose and ears will be in the exact same proportion as they are with the longer lens, if the two lenses are in the same position ( strictly speaking it is their entrance pupils that are in the same position).

 

[greybeard]

I have to agree with the contention that perspective is solely the product of camera to subject distance.

 

[Samerr9]

I am enjoying reading all the detials and physics! HelenB you really took me back to the school days with your posts

I would like to add something although I know less than most of you. I am not talking physics but it is just what I see in my photos and I will stick to in studio photos. Wide angle lenses by its nature will capture more area (or background) than tele at the same position. This is a disadvantage for wide lenses as you might see light stands or the cieling in the photo, while the tele will show less background i.e. only the backdrop.

Furthermore, if we take in consideration the fisheye lens (which is an extreme wide angle). By its nature it will make things in a circle shape thus humans will look compressed in the top and the bottom which is not bad depending on the purpose of the shot. But for studio shots it is not flatering for the final product of a fashion or beauty full body shot in studio. To prove that distortion is not always bad, I read that some erotic photographers use 24mm when shooting ladies to make some parts of their bodies more dominant.

Before I read the physics above, I was kind of convinced that I need to shoot at 85mm, it made sence to me. Lets see where this will lead and I am open to any conclusion.

 

[Robin Usagani]

Samer, fisheye is a different ballgame since it is a non linear lens.

The argument was not about capturing more ceiling and background. I think we all can agree the longer lens will look better if you compare it with the same body. The argument is 35mm with a crop body vs 50mm with a full frame body. You will have almost the same about of FOV so your working distance will be close.

I am enjoying reading all the detials and physics! HelenB you really took me back to the school days with your posts

I would like to add something although I know less than most of you. I am not talking physics but it is just what I see in my photos and I will stick to in studio photos. Wide angle lenses by its nature will capture more area (or background) than tele at the same position. This is a disadvantage for wide lenses as you might see light stands or the cieling in the photo, while the tele will show less background i.e. only the backdrop.

Furthermore, if we take in consideration the fisheye lens (which is an extreme wide angle). By its nature it will make things in a circle shape thus humans will look compressed in the top and the bottom which is not bad depending on the purpose of the shot. But for studio shots it is not flatering for the final product of a fashion or beauty full body shot in studio. To prove that distortion is not always bad, I read that some erotic photographers use 24mm when shooting ladies to make some parts of their bodies more dominant.

Before I read the physics above, I was kind of convinced that I need to shoot at 85mm, it made sence to me. Lets see where this will lead and I am open to any conclusion.

 

[Samerr9]

Samer, fisheye is a different ballgame since it is a non linear lens.

The argument was not about capturing more ceiling and background. I think we all can agree the longer lens will look better if you compare it with the same body. The argument is 35mm with a crop body vs 50mm with a full frame body. You will have almost the same about of FOV so your working distance will be close.

This I don't know, I never used FF.

Maybe someone that have both FF and crop bodies can help us resolve this and post photos as examples to be discussed?!

 

[Robin Usagani]

HelenB, how about when we start talking about barrel distortion? How does 24mm on crop measure with 35mm on full frame?

I really need a diagram or sketch hahah. I cant follow this conversation with only text. The only time I have ever learned about lenses was when I was in college taking physics I.

 

[Robin Usagani]

Samer, fisheye is a different ballgame since it is a non linear lens.

The argument was not about capturing more ceiling and background. I think we all can agree the longer lens will look better if you compare it with the same body. The argument is 35mm with a crop body vs 50mm with a full frame body. You will have almost the same about of FOV so your working distance will be close.

This I don't know, I never used FF.

Maybe someone that have both FF and crop bodies can help us resolve this and post photos as examples to be discussed?!

Kundalini has done one... maybe someone can find that thread. The FOV was similar but if I remember correctly, the background is a little different. However it can be cause by different things. The location of the sensor was not exactly the same. I have tried the same test and I cant seem to overlay the 2 images. I have sold my crop sensor. Ill see if I can find the thread.

 

[Robin Usagani]

http://www.thephotoforum.com/forum/...rence-between-full-frame-cropped-sensors.html

 

[greybeard]

35mm on a 1.5 crop frame would be like a 52.5mm FF (Nikon) and 35mm on a 1.6 (Canon) would be like a 56mm. So it depends on your sensor. You are really splitting hairs. I've used 35mm FF film for years and the perspective from a 50mm on FF is very similar to 35mm on my crop frame. DoF however is shallower f/stop for f/stop with the FF 50mm over the APC-C 35mm. But, back to the OP, using a 35mm with a crop frame camera will give you a natural perspective with a full body portrait. Natural meaning the nose won't be exaggerated as when you are too close with a wide angle and things won't look too flat as with a really long tele. The perspective will look similar to the way one would view the scene with the naked eye.

 

[KmH]

I know of no one more technically astute about photography and photography related subjects here at TPF - than Helen B.

When she explains things, pay close attention because you are getting first rate information.

 

[Robin Usagani]

Damn.. I hate to say this... I just want to apologize to solarflare and infidel. After doing an hour of reading after I get back from work I would say the FOV is pretty darn close until your distance is super close. When I did this test, I shot a subject only 3 ft away and the 35mm on crop sensor was way more distorted.

 

[Mike_E]

Damn.. I hate to say this... I just want to apologize to solarflare and infidel. After doing an hour of reading after I get back from work I would say the FOV is pretty darn close until your distance is super close. When I did this test, I shot a subject only 3 ft away and the 35mm on crop sensor was way more distorted.

Circle of confusion is confusing.





Edit: hey, it sounds good anyway. LOL