Question on macro photography

[pthoutex]

After reading this tutorial on macro photography: https://www.cambridgeincolour.com/tu...-magnification I now understand that the effective aperture will decrease as the subject distance decreases. I just bought a used Micro Nikkor 200mm f/4D last week, and only has a chance to use it a couple of days ago. When I set the aperture on f/4, as I focused closer, I noticed that the f stop showing in my camera (a Nikon D800) did decrease, to f/4.2, f/4.6, even down to f/5. Is this the way it's supposed to be? Based on the tutorial, I understand the reason, but is it supposed to be actually showing in my camera also? Sorry if this sounds too obvious, but this is the first time I bought a fixed focal length macro lens, and the lens is still under warranty. I need to return it if this is not normal i.e. a defective lens.

Philip
Houston, TX

[Dave Humphries]

After reading this tutorial on macro photography: https://www.cambridgeincolour.com/tu...-magnification I now understand that the effective aperture will decrease as the subject distance decreases. I just bought a used Micro Nikkor 200mm f/4D last week, and only has a chance to use it a couple of days ago. When I set the aperture on f/4, as I focused closer, I noticed that the f stop showing in my camera (a Nikon D800) did decrease, to f/4.2, f/4.6, even down to f/5. Is this the way it's supposed to be? Based on the tutorial, I understand the reason, but is it supposed to be actually showing in my camera also? Sorry if this sounds too obvious, but this is the first time I bought a fixed focal length macro lens, and the lens is still under warranty. I need to return it if this is not normal i.e. a defective lens.

Hi Philip,

Yes it is, Nikon do this for you

I believe Canon and others may not (but I have no experience there).

I have the 105mm Nikkor and that does a similar thing.

Welcome to the CiC forums from ...

[Andrew76]

The Canon's do NOT do that. But, as Dave points out, it is normal for the Nikon. It's interesting that you brought it up, I've never heard of that before.

I can't imagine why that would be a good thing - when I have something that I want to get really close into, I set the aperture where I want it, because that's where I want it. But, there must be an explanation as to why.

I'd be interested in learning!

[pthoutex]

The Canon's do NOT do that. But, as Dave points out, it is normal for the Nikon. It's interesting that you brought it up, I've never heard of that before.

I can't imagine why that would be a good thing - when I have something that I want to get really close into, I set the aperture where I want it, because that's where I want it. But, there must be an explanation as to why.

I'd be interested in learning!

Andrew:

Go to the tutorial, https://www.cambridgeincolour.com/tu...-magnification and go down to the section 'Lens Extension & Effective F-Stop', it's explained pretty well. In a way, if your camera shows you the effective aperture rather than what you thought you set it at, it should be good, no?

Philip

[Andrew76]

I suppose so, never really thought about it, since it isn't an option for me. But then again, I've never really shot with that wide of an aperture for my macro shots either. But that's good info to know!

[pthoutex]

I suppose so, never really thought about it, since it isn't an option for me. But then again, I've never really shot with that wide of an aperture for my macro shots either. But that's good info to know!

Agree with you there. I never shot with wide open aperture on a macro setting either, because then hardly anything will be in focus I brought this up mainly because it showed up while testing my new lens, and never seen this phenomenon before, and I just want to make sure that nothing is wrong with my lens.

[jcuknz]

Obviously Nikon do it right and Canon do not ... to warn you that your actual aperture is changing as you go close IMO
I wonder if it also permits you to focus wide open but closes for the shot?

[ajohnw]

The reason for the slower aperture is much easier to understand when discussed via extension tubes. Normally a lens focuses a fixed size image onto the sensor. When an extension tube is fitted it can be viewed as being no different to the dimensional field of view increasing as subjects move further and further away from a lens. The image size from the lens increases but it's light gathering power remains the same. The image is spread over a larger area so the light levels are proportionally weaker. Take a lens that works normally to 1:1 and an extension tube is fitted to increase this to 0.5:1 or 2x. The image size produced by the lens has been doubled so it will be effectively have 4 times the area and light levels will be correspondingly weaker. The same thing happens when a maco lens can be set to 2x unless the manufacturer takes some steps to offset the effect but it's too extreme to do much about it.

According to Canon the effective aperture is f number x (magnification + 1) eg 2x at F16 comes out at F48 and they do not correct the F number in the display. Pity the depth of field doesn't increase too. As the magnification increases it's always less than it was at 1:1 and even that doesn't correspond exactly to what is shown on the lens which will be when the lens is focused at infinity,

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[xpatUSA]

Agree with you there. I never shot with wide open aperture on a macro setting either, because then hardly anything will be in focus I brought this up mainly because it showed up while testing my new lens, and never seen this phenomenon before, and I just want to make sure that nothing is wrong with my lens.

Nothing is wrong, my micro-Nikkor 60mm does the same thing.

[pthoutex]

Thank you everybody for all your helpful replies, it help ease my mind that I did not buy a defective lens I am a brand new member of this forum, but so far I really like what I've seen. Browsing through the different posts in different areas I saw that every body is always helpful and courteous, unlike another forum that I also frequent, where there are so many snarly people that did nothing but put down others' opinion. Hopefully I can contribute what little I know about photography too.

Philip

[William W]

. . . Browsing through the different posts in different areas I saw that every body is always helpful and courteous, unlike another forum that I also frequent, where there are so many snarly people that did nothing but put down others' opinion.

Interesting comment - and not the first time it ha been made here.
Good that you mentioned it.

WW