Some questions on macro lenses

[Grumpy John]

I am seriously considering purchasing a dedicated macro lens. I have tried extension tubes in the past, but they have been a dismal failure (quite possibly caused by the user), close focus filters are not a consideration because I will be adding more optics between the camera and subject.
I have done a bit of research to find out the differences between a macro lens and a "normal" lens. The main differences I have found are:
- Macro lenses allow you to get closer to the subject
- Macro lenses can produce a 1:1 image size (some macro's can produce greater than 1:1)
- Macro lenses have a flat focus field, versus the curved focus field of a non-macro lens. With a curved field lens, the centre of an image is in focus while the edges are soft(er). This softness is usually compensated for by using aperture to adjust your depth of field, but the effect is magnified when photographing at very close distances and when photographing two-dimensional objects. The flat field of the macro lens is designed to allow the entire image to be in focus without increasing the depth of field. (This I did not know)

I have done a comparison chart of the macro lenses available from my favourite supplier (Digital Camera Warehouse) and the Tokina AT-X 100mm f2.8 AF Pro D Macro comes out at best value. The review from Ken Rockwell is pretty impressive.



"Should you switch a macro lens to a camera with a smaller-than-full-frame sensor, an APS-C sensor for instance, the working distance of the macro lens will remain constant, but the image produced will appear magnified as the cropped sensor is capturing a smaller region in the center of the image circle—a narrower field of view by about 1.5x. For example, that Nikon 200mm macro becomes, effectively, a 300mm macro lens on a Nikon DX camera and will show the same field of view in any photograph taken with an actual 300mm macro lens on a full-frame sensor camera. This effect could make it necessary to back away from the subject in order to properly fill your frame." From Macro photography

Does the above statement mean that if I use the Tokina macro lens, which is for a full frame camera, on my 7DII, give me an image ratio of 1.6:1 instead of the 1:1 ratio it gives on a FF camera?

This will be the first of my macro related questions.

[Isac]

I hope this help a bit John. I don't do a lot of macro but I have the Tamron 60mm 1:1 and it's really sharp.

If one takes a photo of a metric ruler stretched across the frame at 1:1 using a 24x36 FF camera, the number of millimetre marks visible will be 35 full marks with 1/2 mark at either side. The same ruler at 1:1 on APS-C will show 24 full marks with 0.55 mark at either side (25.1mm).
Backing off so that 35 marks show with a 1/2 mark on each side requires only 1:1.5 (0.67x magnification) at capture, but 1.5x more enlargement at print time than the FF image to make a 24x36cm print.

[Grumpy John]

Thanks Isac, the math is doing my head in a tad, but I get the gist. I am assuming that the APS-C body in the example is a Nikon (1.5 crop factor).

Did you Google this?

[Isac]

Yep DuckDuckgo actually - never use Google.
Yes Nikon 1.5 Ours are much BIGGER at 1.6

[HansE]

I think of it like this No math needed Green being the crop sensor You can use an EFS lens on a FF but you still get a cropped picture. as the circle is smaller.

[Grumpy John]

I understand the relationship between FF and APS-C Hans, I was just wondering if using a Macro lens designed for a FF camera that gives a 1:1 image now becomes a 1.6:1 image when used on a Canon APS-C body.

[Isac]

I've enjoyed the ride with all this info and tech talk. I found this on the Bob Atkins site. Well explained in layman's terms. HERE.
With what's below, I might start playing with my Tamron 60MM Macro - seems like it will give the same FOV as a 100MM on FF.

[Grumpy John]

I've enjoyed the ride with all this info and tech talk. I found this on the Bob Atkins site. Well explained in layman's terms. HERE.
With what's below, I might start playing with my Tamron 60MM Macro - seems like it will give the same FOV as a 100MM on FF.

Thanks for going to the trouble of posting this information Isac. I understand the focal length differences between FF and CS cameras and have been doing the conversions for ages. However none of these sites have answered my question regarding the 1:1 ratio and sensor size, until now. This site has answered my question.

"We've seen in the examples above that sensor size can be used to calculate magnification, but the degree of magnification itself depends on focal length and subject distance exclusively (assuming that the lens is not used with any extenders or magnifying filters). Sensor size does not alter magnification. With a fixed focal length and subject distance, an APS-C sensor, for example would just crop the frame compared to a full-frame sensor, not enlarge it. Magnification is a property of the projection, regardless of the size of sensor (or film format) you are using. With a full frame sensor you'd just make calculations using 35mm as the sensor width instead of 22mm, but the subject would then be proportionally larger, cancelling out the sensor size difference."

I agree that this is a very exciting journey and I am really looking forward to getting in to macro. Just waiting on some responses regarding the Tokina lens before I take the leap.

[Isac]

Great explanation of it all John. Makes it easier to understand.

[kevinj]

Buy the lens,go out and play,easy.Seriously,I have the Canon 100mm f2.8L IS and it`s a sweet lens,now my adapter ring for the flash has arrived I`ll be posting more pics.Bonus with Macro lenses,they are awesome Portrait lenses.

[Isac]

If I want something like that I just withhold "favours" and that usually works N-O-T!!

[Grumpy John]

I do jobs around the house for brownie points, but every time I open my mouth I seem to lose them.

[Isac]

Funny how 2 people from the opposite sides of a large country, can share parallel moments.

[Ozzie_Traveller]

G'day GJ

Back in film camera days I certainly played with lots of lenses - and for macro stuff I have used all of 28mm F2,8 + 50mm F2,8 + 90mm F4
The 28mm gave me up to 3:1 magnification whereas the 90mm could only do 1:1
The 28mm often failed as the front of the lens touched the subject - the 90mm had good separation from the subject

Overall the best results - a bit subjective here too - was the 90mm as it also stopped down to F64, whereas the 50mm stopped at F22 and the 28mm stopped at F16

For you - follow the above suggestions - get any of the bluddy lenses above and get on with it !!!
Hope this helps
Phil

[Grumpy John]

Thanks Phil, as I have mentioned the Tokina looks to be the best bang for buck. Putting the hard word out re my birthday being just around the corner, and I'll happily accept an early prezzie.

[HansE]

I am glad you got your answer but you obviously must have known this all along. I don't see how all that verbage was different to the graphic representation. Then again we all perceive things differently. Just do it Grumpy you can grovel later.