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I want to do some beauty portraits. Some of my shots will be from waist up, some of them will be tighter. For example just the face and nothing else in the frame OR a little going back to get the model from chest up to the head and some room on the other side of the picture for a brand name for example for the watch she is wearing on her wrist.

My question is about the Macro lenses and in particular this lens that I am thinking to rent:

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The Pentax SMC D FA 645 90mm f/2.8 ED AW SR Macro Short Tele Macro. With a focal length equivalent to 71mm after sensor crop factor, the 90mm f/2.8 gives you macro lens that’s capable of 1:2 reproduction.

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Is 71mm focal length too short for use cases that I am doing to shoot all of them with that? and is being Macro change anything? I mean although it is 71mm but because it is Macro does it mean still I can use it for tight portrait and fill the frame shots too?

I can also rent their 150mm lens which with crop factor is close to 112mm on 35mm, so which lens do you recommend for which use case that I have?

Thanks.

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  • \$\begingroup\$ You are using the term crop factor in place of the term equivalent. The crop factor applies to the differences of focal length when using a lens designed for a 35mm camera with a full size sensor on a 35mm camera with a smaller sensor (aps-c). When discussing medium format cameras and there lenses we say it is equivalent to x focal length on a 35mm camera. This from the B&H web listing of the lens in question. "The Pentax 90mm f/2.8 D FA 645 Macro ED AW SR Lens is a fast, medium-length lens (equivalent to 71mm in 35mm-format)" \$\endgroup\$
    – Alaska Man
    Jun 27, 2016 at 18:34
  • \$\begingroup\$ @Alaska man: why would one use a different wording for what's essentially the same thing? It's smaller than 1, but it's still a factor and it's used exactly like a crop factor because it is a crop factor. To me, the phrase "with crop factor is close to 112mm on 35mm" is equivalent to saying "the equivalent focal length..." (even without the "on 35mm" at the end), because the only purpose of the crop factor is to calculate FF equivalent focal lengths. \$\endgroup\$
    – null
    Jun 27, 2016 at 21:47
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    \$\begingroup\$ Decades of use of the term equivalent by the industry is why. It has been used for decades before there was ever any digital sensors large or small. The word crop is used because you are using a lens for a full size sensor on a smaller size sensor and therefor effectively cropping down what is seen on the smaller sensor. There is no cropping happening in the case of the focal length equivalent of medium format lenses. A 50mm lens on a medium format camera is the equivalent of 26mm on a 35mm camera. thus it is a wider view. One dose not crop up. pentaconsix.com/35mmequiv.htm \$\endgroup\$
    – Alaska Man
    Jun 28, 2016 at 4:47
  • \$\begingroup\$ The term "format factor" would be better as term for all discussions of lens equivalents as this would not have the the connotation of cropping (making an image smaller.) \$\endgroup\$
    – Alaska Man
    Jun 28, 2016 at 5:04

4 Answers 4

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Focal length is focal length, macro or not.

What makes a macro lens special is that it is designed to have a small closest focusing distance. This allows to take images 1:1 the size of the subject (or 1:2 in this case). Other than that, it can be used like any other lens.

Is 71mm focal length too short for use cases that I am doing to shoot all of them with that?

This depends on what working distance to the model you want. A wider lens will allow you to work in a smaller studio.

I can also rent their 150mm lens which with crop factor is close to 112mm on 35mm

A longer lens will give you more compression. Very roughly speaking this means that you will see more model and less background in the image.

For example lets say she is wearing a necklace. And I want her face and necklace and some background room for the brand name to be in the photo. Which one would you use? 71mm Macro? or 112mm tele?

I'd go for the 71mm, depending how much of the background is covered up by the brand name and should be part of the image. But then maybe you want to add the brand name in a more subtle way and have it partially covered up by the model (but still recognizable) which would mean you need less space in the background and could use a longer lens.

The basic question is do you want more model and less brand name in the image? Go for the longer lens (112mm). Otherwise, choose the wider lens.

The two focal lengths aren't dramatically different. I guess you could achieve good results with either one. If the motivation behind the question is that you have different looks and thus want to use different lenses, then I'd suggest to rent two lenses that are further apart focal length wise. So you get a real difference.

As always, if possible, take an available equivalent camera system and do some test shots.

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  • \$\begingroup\$ For example lets say she is wearing a necklace. And I want her face and necklace and some background room for the brand name to be in the photo. Which one would you use? 71mm Macro? or 112mm tele? The studio is long! I can get far back if need be. \$\endgroup\$
    – Brandon
    Jun 27, 2016 at 16:39
  • \$\begingroup\$ @Blake I added some more thoughts. I don't think the lenses are different enough to make a clear decision for either one. \$\endgroup\$
    – null
    Jun 27, 2016 at 16:55
  • \$\begingroup\$ thanks, my main concern with 71mm was about face distortion possibility but then it is a macro so can get close to her face.. then it is 71mm , distortion when too close .. so got me confused \$\endgroup\$
    – Brandon
    Jun 27, 2016 at 17:05
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    \$\begingroup\$ @Blake 71mmE is by no means going to let you get "too close", unless you want to take pictures of their eyelashes, rather than headshot / chest up / etc. \$\endgroup\$
    – hobbs
    Jun 27, 2016 at 19:06
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    \$\begingroup\$ The answer totally ignores the issue of perspective. The lion's share of facial distortion is not caused by a lens' focal length. It is caused by a shooting distance that means the nearest parts of a subject's face are significantly closer to the film/sensor than the far parts of the subject's face. \$\endgroup\$
    – Michael C
    Jun 28, 2016 at 1:24
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The distance, camera to subject determines the perspective of the image. Consider, things close to the camera reproduce large, and things further away, reproduce small. If you work in too close, the nose reproduces too big and the ears too small. We are taking distortion. It is mainly distortion of the facial features that causes the subject to say, “I look treble – I don’t photograph well”. The remedy is to simplely step back. Most portraits are best if a moderate telephoto is used. A rule of thumb is to use a lens with a focal length of about 2 ½ times the diagonal of the format of the camera. For the full frame, that’s about 108mm. For the compact digital, that’s 75mm. It makes no difference if the lens is a zoom or fixed or micro, the key is to try and step back. This can be difficult as we naturally try to fill the frame and not leave empty space around the principle subject. Moderate telephoto to the rescue: such a lash-up forces us to step back and this action delivers a perspective that is a close match to what the subject perceives i.e. their view of themselves in the makeup mirror.

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  • \$\begingroup\$ Or in the case of the medium format camera referenced in the question, the sensor diagonal is about 55mm, so 2.5x the diagonal is about 140mm. \$\endgroup\$
    – Michael C
    Jun 28, 2016 at 1:27
  • \$\begingroup\$ Very much this. \$\endgroup\$
    – Carl Witthoft
    Jun 28, 2016 at 12:10
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Because it is a macro, you can go closer than usual. You can use it for things like jewelry, wristwatches etc.

Consider if 70mm equivalent is not too wide for headshots, though. I believe fashion photographers usually prefer flat look that is typical for longer focal lengths.

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  • \$\begingroup\$ For example lets say she is wearing a necklace. And I want her face and necklace and some background room for the brand name to be in the photo. Which one would you use? 71mm Macro? or 112mm tele? \$\endgroup\$
    – Brandon
    Jun 27, 2016 at 16:39
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    \$\begingroup\$ I would probably prefer the longer lens, but all depends on the available space - longer lens requires longer shooting distance and bigger rooms... \$\endgroup\$
    – MirekE
    Jun 27, 2016 at 17:08
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Why are you wanting to use a macro lens for a portrait shot?

Maybe you have considered this but why would you not use a 200 f2 or a 135 dc or a 70-200 f2.8?

These will give the distance, sharpness, and be flattering to the person. I understand you are also showcasing product.

What is your end goal? How will this be used? What size will the print be?

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  • \$\begingroup\$ That is probably more a comment than an answer. \$\endgroup\$
    – Olivier
    Jun 28, 2016 at 17:37

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