100mm macro question

[MDJAK]

As some of you know, I'm not both a Nikon and Canon owner and like them both. So here's my question.

I almost purchased Nikon's new 105mm VR micro (their word for macro) lens. It's a fixed f2.8, just like the 100mm Canon. However, their lens, when you focus at different distances, becomes an f4.8 or so. I asked about that on a Nikon forum and someone stated the Canon lens does that also, that all true 1:1 macro lenses do that, but Canon just keeps it a "secret" by not showing the change in F stop. That sounds like a bunch of hogwash to me.

So, what say you?
me

[poorARTstudent85]

like u said, hogwash. my 100mm macro can stay at f2.8 at all distances. its actually a really great portrait lens too.

[gardengirl13]

What? I don't get how if you change distnace the f stop changes? I've never heard of that?

[poorARTstudent85]

yea i have no idea who came up with that idea on a 100mm lens. i do know my old kit lens would change from f4.5 to f5.6 when u zoomed from 18 to 55mm. maybe they were confusing it with something like that? idk.

[Johan Groenewald]

I'm not both a Nikon and Canon owner
? so what do you own?
That sounds like a bunch of hogwash to me
Yeah me too. With Canon the choice of aperture is your's. Maybe the nikon is thinking with the green box

[bob-e]

Aperture change at 1:1 sounded weird, so I looked it up:

Nikon review from photozone "At 1:1 the max. aperture decreases to f/4.8 which is a quite typical characteristic for an IF (internal focusing) macro lens. The adjusted aperture value is displayed in the viewfinder"

Photozone's Canon review doesn't state this.

[gjl711]

Zoom lenses will change aperture as you zoom in. Building a zoom lens that does not change aperture is a expensive undertaking. However, prime lenses do not do that. I am surprised that the Nikor lens may or may not do that. F-Stop is simply the ratio of the focal length to the diameter of the aperture opening and should have nothing to do with the distance it is being focused at.

[Tony-S]

I think the issue is that magnification reduces the amount of light striking the sensor. If you remember the dark room days, the higher the enlarger head from the paper, the longer exposures you had to make because the light was spread over a greater surface area. Perhaps the Nikon lens reports this to the camera, while the Canon (and Sigma, for that matter) doesn't?

[Jon]

As some of you know, I'm not both a Nikon and Canon owner and like them both. So here's my question.

I almost purchased Nikon's new 105mm VR micro (their word for macro) lens. It's a fixed f2.8, just like the 100mm Canon. However, their lens, when you focus at different distances, becomes an f4.8 or so. I asked about that on a Nikon forum and someone stated the Canon lens does that also, that all true 1:1 macro lenses do that, but Canon just keeps it a "secret" by not showing the change in F stop. That sounds like a bunch of hogwash to me.

So, what say you?
meIt's true. If you're computing exposure from an external meter or using flash guide numbers, you need to allow for the extension of the lenses. A 100 mm lens f/2 (for ease in math) with an additional 100 mm of extension will have a physical aperture of 100 mm/f/2=50 mm. Now since you've got 200 mm of total lens extension, the effective aperture is 200 mm/50 mm = f/4. If you're using TTL metering, this is transparent to the camera. But meter a grey card with the lens at infinity and again at 1:1 and compare the readings.

Canon's 50 mm f/3.5 FD SSC macro came with a 25 mm extension tube to get it from 1:2 to 1:1; when you mounted the lens to the tube, it went on upside down where there was a second aperture scale and range/magnification scale covering that range.

Incidentally, Mark, if it's really an f/4.8 at 1:1, it's only an 85 mm lens at that magnification. This isn't surprising as internal-focusing lenses actually change the focal length as part of the focusing process in order to keep the length of the lens relatively constant. Canon's 100 mm macro's somewhere around a 68-70 mm lens at 1:1 in reality, IIRC.

[scot079]

See AeroSmith's post about 1/3 down

http://photography-on-the.net/forum/showthread.php?t=208589&page=2

According to the MP-E's manual: effective f/stop = f/stop x (magnification + 1)

If I did the math right, f/2.8 = effective aperture is f/5.6 @ 1:1 mag. Maybe this has something to do with it?

[gasrocks]

http://www.naturfotograf.com/lens_surv.html#top1

The NIkon VR macro is not as good as the older non VR model.

[scot079]

BTW MDJAK, have you already tried an MP-E 65mm? Some Nikon shooters I've spoke with are quite jealous and wish Nikon (or 3rd party) made something comparable.

[Lester Wareham]

As some of you know, I'm not both a Nikon and Canon owner and like them both. So here's my question.

I almost purchased Nikon's new 105mm VR micro (their word for macro) lens. It's a fixed f2.8, just like the 100mm Canon. However, their lens, when you focus at different distances, becomes an f4.8 or so. I asked about that on a Nikon forum and someone stated the Canon lens does that also, that all true 1:1 macro lenses do that, but Canon just keeps it a "secret" by not showing the change in F stop. That sounds like a bunch of hogwash to me.

So, what say you?
me

Yes all macro lenses suffer light loss, the Nikon system shows the actual effective aperture and the Canon system shows the set aperture.

It is not a secret, the systems just work differently; before fancy electronics you set the f-stop mechanically and there was not normally a way for the compensation factor to be shown, although some medium format cameras with bellows focusing were large enough to show a compensation scale.

The eff aperture = set aperture * (M/P+1) where M is the magnification and P is the lens pupilary magnification (the exit (rear) pupil size divided by the entry (front) pupil size).

This relashionship is fairly easy to derive for a symmetric lens with overall linear extension focusing but things are more complicated with internal focus lenses. For a simple lens like the former you always loose two stops at life size.

Measurements indicate the 100mm f2.8 macro also looses 2 stops of light, this doesn't show in the f-stop display but you can see it in the metered shutter speed.

[Lester Wareham]

http://www.naturfotograf.com/lens_surv.html#top1

The NIkon VR macro is not as good as the older non VR model.

Aparantly Nikon's own documentation states that the VR is increasingly ineffective below a magnification of 1:60 (from memory) and almost useless at life size.

This is probably why Canon haven't produced a IS macro lens, the extra optics would probably reduce sharpness but the IS would only be of limited use.

BTW MDJAK, have you already tried an MP-E 65mm? Some Nikon shooters I've spoke with are quite jealous and wish Nikon (or 3rd party) made something comparable.

Yes the MP-E 65mm is a fantastic lens, the lens of choice for small insects. Essentially a short mount macrophoto lens integrated with a telescoping "extension tube" and an electronic aperture giving autostop down.

The Nikon world is still in the bellows and short mount lenses paradigm of Canon FD systems, not very usable in the field.

On the other hand I think Nikon have a very nice looking PC-macro lens giving 1/2 life size and tilt/shift . http://www.nikonusa.com/Find-Your-Nikon/Product/Camera-Lenses/1458/PC%20Micro-NIKKOR%2085mm%20f/2.8D.html

But of course the Canon owner can use the TS-E 90mm with tubes.

[amfoto1]

But of course the Canon owner can use the TS-E 90mm with tubes.

I want to give that a try some time. I have the other two TS-E lenses and find them quite useful, but have held off getting the 90mm until I was shooting full frame again more of the time.

The 90mm must get pretty close to 1:2 or half life size. I don't know the exact magnification it gives, but it focuses as close as .5m (1.6 ft.) all on it's own, so wouldn't need much additional extension. (Compare to the 100/2.8 Macro, which focuses as close as .31m, 1 ft., for 1:1.)

Cheers!

[Lester Wareham]

I want to give that a try some time. I have the other two TS-E lenses and find them quite useful, but have held off getting the 90mm until I was shooting full frame again more of the time.

The 90mm must get pretty close to 1:2 or half life size. I don't know the exact magnification it gives, but it focuses as close as .5m (1.6 ft.) all on it's own, so wouldn't need much additional extension. (Compare to the 100/2.8 Macro, which focuses as close as .31m, 1 ft., for 1:1.)

Cheers!

It has a max mag of 0.19X
Canon specify the following magnification with the EF 12 & EF 25 tubes 0.43-0.14X & 0.60-0.31X

;)