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07-25-2013, 10:06 AM   #1
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Best Focal Length for macro work

Im fairly new to DSLR cameras so excuse any ignorance I may show in the following question. I have tried to do a search on this subject but without success; if I have missed something again I am sorry please point me in the right direction.

I am looking for a macro lens to photograph historic coins specifically Roman Denarii, which are about 18mm in diameter, and silver in colour. Due to their age they tend to be badly worn, so the key attribute of any lens has to be sharpness; I do not want to lose what little definition remains in the coins. I intend to photograph indoors, using a tripod and natural light from a window to the side (to maximise shadows and hence improve the perception of the highs and lows on the faces of the coins)

Would a shorter focal length (eg the 35mm limited) give better or worse results than longer (eg 100mm DFA macro)? What are the relative advantages and disadvantages of each when it comes to shooting small items that do not move in a controlled environment?

I doubt I will be doing much insect shooting, so the longer closest focus distance of the 100mm is not an advantage. I do not use either focal length more than the other at present (using the kit lenses on my K-r) so please ignore the strengths and weaknesses of each lens for other purposes.

This will be my first prime.

Any ideas?

07-25-2013, 10:12 AM   #2
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A shorter minimum focus distance can be annoying even in a controlled environment when dealing with lighting.
07-25-2013, 10:17 AM   #3
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have you tried macro filters...would be alot cheaper then a macro lens
07-25-2013, 10:31 AM   #4
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Extension tubes are worth a thy. They can be had for less than $10 on ebay.

07-25-2013, 10:45 AM   #5
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Focal length will mostly change the working distance. You can get the same size image with the 35mm macro as you can with the 100mm macro, because they both have the same 1:1 magnification ratio. The 100mm lens lets you be further away so the lighting setup is easier.

You don't have any need for autofocus or P-TTL flash so a good manual macro would be OK.
07-25-2013, 10:46 AM   #6
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You don't need to buy a new macro lenses but you can also go for an older one with only manual focus, you don't use AF with macro.

I do advice to go for a macro lens for reproductions because of their flat focus plane.

About the focal length, it does not matter for the quality although 35mm is quite short when you also want to use flash light for example.
07-25-2013, 10:48 AM   #7
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Hello Redundant Banker, welcome to the Forum!
My recommendation is the 100mm macro lens, as it allows more room for natural lighting and/or flash fill lighting. You will find that some subjects and lighting situations cause the lens to cast a shadow on the work, especially in very-close focusing photos.
Here is an example of a 90mm macro lens with 1:1 adaptor, roughly equal (in view) to the Pentax DFA 100mm which is also 1:1 magnification.
The lighting was weak sunlight from the right and a stronger diffused flash from the left. The silver dial is just under 6mm in diameter, the silver pointer is 6.1mm long and the lettering is 1.8mm high. The mainspring (partly shown) is 18.2mm in diameter and the entire pocketwatch is 47mm in diameter.
The camera was tripod mounted with a cable release and I hand-held the flash at various positions on the left, trying different angles of light. Exposure time was1/2s. The lens is a Vivitar Series 1 90mm f/2.5 macro, also known as the 'Bokina'.
Hope this helps!
Ron
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07-25-2013, 10:53 AM   #8
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If photographing small relatively flat objects you probably would want a dedicated prime macro as optically the field is nearly flat so you'll get less distortion at the edges.

The longer the focal length the more working distance you should have between the front element and the object being photographed. This gives you much more flexibility in lighting. However the larger working distance can be a disadvantage in close quarters.

If you need more than 1x magnification you will need to use either close-up lenses (loss of image quality) or tubes/bellows. By adding extension you decrease the working distance. If the lens doesn't have an aperture ring you'll need tubes with electrical contacts. A 50mm prime macro should suit you unless you need to add extension. But again a 100mm will give you more flexibility.

I would use a copy stand rather than using a tripod if all you are going to photograph are coins.

Sharpness should not be a concern if you stay away from budget prime macro lenses. As the saying goes "Nobody made a bad macro lens" (nobody being the "big" lens makers). Sigma and Tokina macro lenses should be of good quality.

07-25-2013, 11:00 AM   #9
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The main problem with too short a focal length is that the shadow from the lens may cover your subject, depending on the angle of the light.

100mm should be safe here. 50mm may be safe. I'd be cautious about getting a 35mm macro lens for this purpose.


While it's true AF isn't necessary, make sure you have some way of getting good focus, whether it's through live view or some other method. Anything from a Cosina 100/3.5 or older MF Pentax macro to a DFA 100/2.8 WR may be satisfactory. You don't need to go all the way to 1:1 (unless you're doing detail crops) since an 18mm coin won't quite fit on a 16mm high sensor.
07-25-2013, 11:20 AM   #10
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I like the 90mm to 100mm range ... shot once with a 50mm and found it too close. Cannot image a 35mm Macro ...

Currently, my favorite is the D-FA 100/2.8 Macro WR ... a super lens! Next is a Tamron AD2 SP 90/2.5 (52BB), followed by the Pentax M 100/4 ... but note that these lens are only 1:2, so I use tubes with the M and a Tamron 2X TC with the other. Also had the newer Tamron AF 90/2.8, but sold it to finance the D-FA.

Good luck with your search, J
07-25-2013, 11:25 AM   #11
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QuoteOriginally posted by Redundant Banker Quote
Im fairly new to DSLR cameras so excuse any ignorance I may show in the following question. I have tried to do a search on this subject but without success; if I have missed something again I am sorry please point me in the right direction.

I am looking for a macro lens to photograph historic coins specifically Roman Denarii, which are about 18mm in diameter, and silver in colour. Due to their age they tend to be badly worn, so the key attribute of any lens has to be sharpness; I do not want to lose what little definition remains in the coins. I intend to photograph indoors, using a tripod and natural light from a window to the side (to maximise shadows and hence improve the perception of the highs and lows on the faces of the coins)

Would a shorter focal length (eg the 35mm limited) give better or worse results than longer (eg 100mm DFA macro)? What are the relative advantages and disadvantages of each when it comes to shooting small items that do not move in a controlled environment?

I doubt I will be doing much insect shooting, so the longer closest focus distance of the 100mm is not an advantage. I do not use either focal length more than the other at present (using the kit lenses on my K-r) so please ignore the strengths and weaknesses of each lens for other purposes.

This will be my first prime.

Any ideas?
On APS-C, my personal favorite is 100mm, whereas on FF, I like 150mm (i.e. the Sigma 150mm F2.8 macro). It really depends on how close you want your working distance to be and what kind of magnification you're aiming for, though!

Adam
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07-26-2013, 12:58 AM   #12
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Thanks to everyone for their replies. It looks like the 100mm macro lens is the winner.

I had never heard of a copy stand before. Having just done a quick Google search, this seems to be an excellent idea, so thank you Not a Number. Anything in particular I should look out for, or avoid, when chosing one?
07-26-2013, 02:12 AM   #13
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Re: copy stands

Make sure the column is tall enough that you can have the camera far enough away for the magnifications you'll be using. Since you'll be shooting most likely near 1x it should not be a problem. In the film era the user manuals usually had tables of the magnification and object to film plane distances. From the Kiron 105mm macro manual the distance for 1x is 1.14 ft (0.347 m). For about 0.5x 2.3 ft (0.701 m). If you think you will be changing the magnification often consider spending the money to buy a unit with a geared column or damping to allow one-handed operation. It would probably be wise to use both hands regardless - you won't be very happy if the whole thing slips down the column and the lens crashes into the board.

You can always improvise lights with a pair of articulated or goose-neck desk lamps if need be.
07-26-2013, 03:46 AM   #14
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Check out Mark Goodman's coinimaging.com, lots of great info there (much of which is applicable to any sort of macro work, not just coin photography).

18mm is a bit greater than the smaller dimension of the sensor on your K-r. Hence to photograph the entire coin in one shot means you are at slightly below 1:1 magnification. The advice to use a 100mm lens is good, as at this magnification you will have a good amount of working distance making lighting easier to manage. But I wouldn't consider this a requirement; for coins (as for most subjects) you want your light source(s) to be diffuse and mainly from the sides, not straight on. If you are willing to consider short working distance setups you have lots of options, including some fairly low-cost options capable of producing exceptional results (I'm mainly thinking of reversed lenses).
07-26-2013, 12:37 PM   #15
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For shooting coins with my K-x or K-30 and the Tamron 90, I have used this generic Gorillapod. (Link is to my review of it.) Cheap, works great.
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