Tips, Suggestions, Advise For Using Macro Extension Tubes

[JBPhotog]

FWIW, micro or as some would call them macro lenses are corrected to be flat field whereas most non-micro(macro) lenses have a curved field. Therefore nailing focus across a flat subject isn't possible with curved field lenses since the focus point across the image plane is an arc. Depending on the subject and the level of magnification this may or may not be an issue. One can test a lenses curved field by shooting a flat subject with the camera perpendicular to the surface while noticing the centre and edge sharpness.

As mentioned by others, a closed down aperture gives you better DoF but also can introduce diffraction if one goes beyond the lenses sweet spot but you already know that since you have rails and stacking produces sharper images with this method. For some fun, try that 6mm tube on a wide lens, you get the wide field of view with the ability to get up close.

 

[adamhiram]

For some fun, try that 6mm tube on a wide lens, you get the wide field of view with the ability to get up close.

Funny you should mention that! I have an 11-16mm lens with a minimum focusing distance of about 12", and wanted to be able to focus even closer. I tried using my shortest extension tube, 12mm, and wound up with a focusing distance range entirely inside the lens. Now I'm curious if a 6mm tube would actually make it usable, although I'm not sure it would be worth the effort to seek one out.

 

[Derrel]

Short lenses demand short extension tubes; years ago Nikon introduced the K-ring set, with the shortest tube being a 1mm, as I recall. A Full set consists of K1,K2,K3,K4,K5 rings.

 

[Derrel]

field curvature can be a real problem; at 30 feet, it is seldom an issue at smaller apertures, but at 30mm, a bit of curvature can be a deal-breaker.

 

[Derrel]

"Funny you should mention that! I have an 11-16mm lens with a minimum focusing distance of about 12", and wanted to be able to focus even closer. I tried using my shortest extension tube, 12mm, and wound up with a focusing distance range entirely inside the lens. Now I'm curious if a 6mm tube would actually make it usable, although I'm not sure it would be worth the effort to seek one out."

Nikon's VERY short K-ring set was designed for use with such short lenses.

 

[Soocom1]

OK. So I am now playing with this also.

The extension issue through my playing around yielded an interesting result that though I already knew, had trouble associating until I tried it.
Mounting a 200mm to tubes. this allowed me to focus on some really small detail from a goodly distance.
The biggest problem as stated above is that the DoF is extremely limited.

So if I am reading this correctly, if I use a lens with a fairly large front element, Ill be getting alot more light, but the aperture will cut down and balance it out. is that correct?

I am asking because I am thinking of trying one of my large med. format lenses hooked to macro tubes.

yes? No?

 

[JBPhotog]

OK. So I am now playing with this also.

The extension issue through my playing around yielded an interesting result that though I already knew, had trouble associating until I tried it.
Mounting a 200mm to tubes. this allowed me to focus on some really small detail from a goodly distance.
The biggest problem as stated above is that the DoF is extremely limited.

So if I am reading this correctly, if I use a lens with a fairly large front element, Ill be getting alot more light, but the aperture will cut down and balance it out. is that correct?

I am asking because I am thinking of trying one of my large med. format lenses hooked to macro tubes.

yes? No?

The F-stop on your lens is a fraction of the aperture diameter so the front element is factored into that equation. All this means you won't get any more light than the actual minimum aperture of the lens. By adding an extension tube you are increasing the distance of the lens elements from the sensor plane, by increasing the magnification a loss of light also occurs.

For many lenses, by focusing to the minimum distance also results in a slight loss of light.

 

[JBPhotog]

I used to own a Nikon K1 ring and when mounted to my 24mm F2.8 incredible close-ups were possible with a really wide field of view. Sadly as I transitions into digital they hit the market. I do still own my PK-13 ring bought @ 40 years ago and works on my 85mm PC lens.

 

[Soocom1]

OK. So I am now playing with this also.

The extension issue through my playing around yielded an interesting result that though I already knew, had trouble associating until I tried it.
Mounting a 200mm to tubes. this allowed me to focus on some really small detail from a goodly distance.
The biggest problem as stated above is that the DoF is extremely limited.

So if I am reading this correctly, if I use a lens with a fairly large front element, Ill be getting alot more light, but the aperture will cut down and balance it out. is that correct?

I am asking because I am thinking of trying one of my large med. format lenses hooked to macro tubes.

yes? No?

The F-stop on your lens is a fraction of the aperture diameter so the front element is factored into that equation. All this means you won't get any more light than the actual minimum aperture of the lens. By adding an extension tube you are increasing the distance of the lens elements from the sensor plane, by increasing the magnification a loss of light also occurs.

For many lenses, by focusing to the minimum distance also results in a slight loss of light.

True that.

But the apature f-number is relative.
So an f-22 for a canon 18-135 may be an actual 3.5+/- mm in diamiter, while a f-22 for 300mm Mamiya 645 lens may actually be say 7mm in size. This may only seem like a small increase but would overall be more actual light hitting the sensor v. that of the canon lens.

ergo: a slightly wider DoF with the larger lens with the same f-22.

 

[adamhiram]

if I use a lens with a fairly large front element

On a less technical note, you are a lot more likely to block the light illuminating the subject when shooting really close! This is why I had much better results with the 18-55 kit lens that came with my first SLR than with a larger constant 2.8 lens - the bigger lens was sharper, but the larger front element blocked the light and limited how close I could get. I found I had the best results with a 50mm lens, or with a telephoto if I just wanted to get closer - just need to be careful of the weight of the lens on the tubes.

 

[smoke665]

@adamhiram So even stopped down, I couldn't seem to get the tack sharp focus that I was wanting on on the 135mm. I tried different rings, stacking them, etc. the result was pretty much the same, it was okay sharp, but not what I would have expected. My DA35mm ltd. macro, with a MFD of 12" can nail an edge so sharp it almost cuts you. The other thing I'm finding is with the manual extension it limits me to live view only for focusing, which is dependent on contrast detection as opposed to the view finders phase detection. Like you I'm thinking I need to experiment with some other lenses in the bag.

 

[JBPhotog]

OK. So I am now playing with this also.

The extension issue through my playing around yielded an interesting result that though I already knew, had trouble associating until I tried it.
Mounting a 200mm to tubes. this allowed me to focus on some really small detail from a goodly distance.
The biggest problem as stated above is that the DoF is extremely limited.

So if I am reading this correctly, if I use a lens with a fairly large front element, Ill be getting alot more light, but the aperture will cut down and balance it out. is that correct?

I am asking because I am thinking of trying one of my large med. format lenses hooked to macro tubes.

yes? No?

The F-stop on your lens is a fraction of the aperture diameter so the front element is factored into that equation. All this means you won't get any more light than the actual minimum aperture of the lens. By adding an extension tube you are increasing the distance of the lens elements from the sensor plane, by increasing the magnification a loss of light also occurs.

For many lenses, by focusing to the minimum distance also results in a slight loss of light.

True that.

But the apature f-number is relative.
So an f-22 for a canon 18-135 may be an actual 3.5+/- mm in diamiter, while a f-22 for 300mm Mamiya 645 lens may actually be say 7mm in size. This may only seem like a small increase but would overall be more actual light hitting the sensor v. that of the canon lens.

ergo: a slightly wider DoF with the larger lens with the same f-22.

Hmm if I understand you correctly, you might want to check your source on this as it contradicts every aspect of lens design. If your scenario were true, then all light meters that have ever been produced would have had an additional input for format and focal length, which of course they don't. The exposure triangle has always been accurate meaning at a given ASA/ISO the luminance level produces a correct exposure with the other two components, shutter speed and aperture. No focal length or format input is required. IE, at 100 ISO F16 and 1/100 sec produces a proper exposure on a sunny day between the hours of 10:00 and 14:00 focused at infinity on any format, 16mm to 8x10.

Also, given the same focal length, say a 105mm F2.5 and a 105mm f1.4, they produce the exact same DoF at the same aperture(say f8) despite the 105mm f2.5 having a 52mm front thread vs the 105mm f1.4 an 82mm front thread.

 

[Soocom1]

Also, given the same focal length, say a 105mm F2.5 and a 105mm f1.4, they produce the exact same DoF at the same aperture(say f8) despite the 105mm f2.5 having a 52mm front thread vs the 105mm f1.4 an 82mm front thread.

Ever shot a MF lens on a FF or crop slr?

 

[adamhiram]

So even stopped down, I couldn't seem to get the tack sharp focus that I was wanting on on the 135mm

I am curious if the issue is technique or just limitations of the equipment. My understanding is that using extension tubes sacrifices a little in both light transmitted and overall sharpness, but it shouldn't be too dramatic. Here is a test shot I took of a penny using a 50mm f/1.8 lens with 68mm of stacked extension tubes (36+20+12), for a focusing distance of just under 1", and stopped down to f/16. I don't own focusing rails, so I just stacked some 1/16" scraps of masonite until I got close, then used the lens's focus ring for fine adjustment. Are your results significantly softer than this?


20190617-DSC_2907a by adamhiram, on Flickr

 

[JBPhotog]

Also, given the same focal length, say a 105mm F2.5 and a 105mm f1.4, they produce the exact same DoF at the same aperture(say f8) despite the 105mm f2.5 having a 52mm front thread vs the 105mm f1.4 an 82mm front thread.

Ever shot a MF lens on a FF or crop slr?

No but I have shot 16mm to 8x10 as well as 35mm and 6x6 cm at the same time, same film speed, same aperture and same shutter speed with identical exposures. Math doesn't change based of format.

Notice how this calculator doesn't ask how big the front element is of a 105mm. Because F5.6 is the ratio of the focal length divided by the diameter of the aperture.

With respect to the OP, a conversation about mixing different format lenses should be in a new thread.