Jump to content

Recommended Posts

I have been shooting macro with my 100mm and find the depth of field quite narrow - so trying to capture a nudibranch for example I can usually only get a small portion in the sharp focus range ( yes I have experimented with different apertures). So my question is given the same scenaro would a 60mm macro lens give me a greater DOF?

Share this post


Link to post
Share on other sites

Nikon glass, 60 vs 105, both at F22 - Seems like the 105 definitely has a shallower DOF... these were taken on a DX (crop) sensor body.
60mm

12530959283_0256899bd0.jpg

 

105mm
12530983283_b0442987d0.jpg

 

HTH

Share this post


Link to post
Share on other sites

In general it is true that for the SAME MAGNIFICATION then DOF is independent of focal length. But, for example longer focal lengths might lead to more magnification in the background leading to an apparent DOF increase. I think the examples above are a bit confusing in that the 60 was shot much less closely than the 100 so the effect is a bit exaggerated.

Bill

Share this post


Link to post
Share on other sites

Humm, Thought I had a answer with CamelToad's response then bvanant got me confused - question might be confusing. I know I'd be physically closer to the subject - so with that in mind will I have a deeper depth of field with the 60mm? I personally prefer the first Nudibranch image above with more of the subject in focus. It appears there would be more latitude with the 60mm to be able to get the entire subject in focus but open up the f stop and you can get the same dof as the 100mm if that is what effect you want. Would this be logical thinking?

Share this post


Link to post
Share on other sites

At the same magnification AND the same aperture the DOF is the same, as is the resolving power (the smallest features that can still be detected). At the same distance and aperture the 60mm will give greater DOF but less magnification and less resolving power. Of course you could achieve the same with the 100mm by moving backwards a bit if water clarity allows.

 

Because resolving power and DOF both depend on interference of light waves you can't improve one without hurting the other. You just have to decide what you want from your image and optimize for that. Shooting from a direction where your object is as 2D as possible helps to but for composition head shots are normally prettier.

 

Bart

Share this post


Link to post
Share on other sites

So Bart, would I have to assume in your scenario that the 105mm would allow me the same depth of field as the 60mm should I choose to move further away from the subject thus forcing me to seriously crop my image to achieve the same affect as the 60mm (final image magnification for presentation)? Just trying to decide if I need to include the 60mm in my arsenal of lenses.

Share this post


Link to post
Share on other sites

Yes, they were shot from different distance as mentioned above. We know this to be true due to the different focal lengths of the lenses used to get the desired magnification/composition/etc for the shot.

 

That said, the shot from the 105 is not cropped at all, while the shot from the 60 was cropped -- it was shot in landscape, and I cropped the image to portrait, leaving the nudibranch the same size as shot in the original raw file. I basically just cut off the sides.

 

I used the 60 a good bit in Lembeh, and I was glad I had it, but I definitely used the 105 a good bit more. If I could only keep one, I would keep the 105.

Edited by CamelToad

Share this post


Link to post
Share on other sites

For me, my go to lens on DSLR was always the 60 mm with a 1.4 teleconverter. That being said in u4/3 I now use either the Oly 60 or the Panasonic 45 for macro stuff.

 

Bill

  • Like 1

Share this post


Link to post
Share on other sites

As Bill says DOF at same magnification does not change the only difference is the field of view

60mm and 105mm bear different working distance to achieve the same magnification and the amount of background behind will change

 

Usually a narrower lens give less background behind and more subject isolation however by being further away you may have less clarity due to particles in the water

 

In terms of sharpness every glass has different performance regardless of focal length, that is also a factor as without sharpness things are garbled

Share this post


Link to post
Share on other sites

So Bart, would I have to assume in your scenario that the 105mm would allow me the same depth of field as the 60mm should I choose to move further away from the subject thus forcing me to seriously crop my image to achieve the same affect as the 60mm (final image magnification for presentation)? Just trying to decide if I need to include the 60mm in my arsenal of lenses.

 

You would not need to crop at all. Once you move back with your 105mm to get the same magnification as the 60mm the images will be the same size. Interceptor121 has a lot of good other comments on field of view and background. Like CamelToad if I had to choose between my canon 100mm and 60mm I would keep the 100mm. And like Bill I am now using m43 with the 60mm which happens to sit right in between the 60mm and 100mm when used on APS-C.

 

I think for most people the two dominant reasons to prefer the 60mm over 100mm is that the former is more versatile because it gives more leeway to get images of larger critters as well as the small stuff without having to back off too much. The other is for people who dive in peasoup and want to get as close as possible. The 100mm advantages are when you want a bit more working distance for lighting or to not scare your subject. I almost exclusively shoot fish for which the latter is important. If my passion was nudibranch I would probably keep the 60mm. A secondary advantage is for those using wet diopters. They give more bang for the buck on longer lenses.

 

Bart

  • Like 1

Share this post


Link to post
Share on other sites

I think though that with u 4/3 the crop factor is more like 2 making the 60 Olympus seem like a 120 on 35 mm film (with slightly different aspect ratio, hence the 4/3 in the name.

Bill

Share this post


Link to post
Share on other sites

In my blog I made a comparision of 30mm, 50mm and 100mm macro lenses taking the same subject at approx. the same magnification:

http://fiberstrobe.blogspot.de/2014/09/put-sel30m35-lens-into-perspective.html

 

You will see that the DOF is the same in all 3 cases (at given F number) but the perspective is completely different. Check especially the relationship with the background (not just the background blur and the field of view, but how the close subject behind the main one looks).

They were taken not underwater but I hope it's helpful.

  • Like 1

Share this post


Link to post
Share on other sites

From what I understand the increase in focal length - to 100mm, from 60mm - results in the distance between foreground and background appearing to be compressed, or flattened on top of one another, like you see when moving backward while zooming in with a telephoto zoom. So much less of the environment can be seen around the subject, and what appears immediately behind the subject is often actually quite far off, and therefore out of focus regardless of using very small apertures?

Share this post


Link to post
Share on other sites

Sponsors

Advertisements



×
×
  • Create New...