Is this true about the Tamron 90mm, f2.8 macro lens?

Started Mar 5, 2014 | Discussions thread
JeffAHayes Senior Member • Posts: 1,968
Re: Is this true about the Tamron 90mm, f2.8 macro lens?

jackdan wrote:

From an Amazon review for the Canon version.

"This lens is only 2.8 at 10 feet to infinity. The maximum aperture drops as you focus closer, and at minimum focusing distance, where many will want to work to get the true 1:1, it is all the way down to 5.6."

I have the Pentax 35mm, f2.8 and am trying to learn the pros and cons of each at taking photos at the minimum focus distance, which I assume is where the max magnification occurs, but am also interested in what the Tamron lens can do for me in general that the 35mm can't, beside shooting insects, and human portraits. One thing in particular I wonder about is how the longer minimum focus distance affects the difficulty to achieve focus at MFD and if it affects the DOF at f2.8 and MFD.

I certainly wouldn't worry about it, either way, as NOT being able to get ENOUGH DOF is generally the major issue I think MOST OF US have with macro lenses. Shorter lenses, such as a 35mm, will definitely give you more DOF per F-stop. The longer the lens is, the LESS DOF you'll get per F-stop. So even if that 90mm F2.8 is really only F5.6 on closeup shots, so long as it still gives you the BRIGHTNESS of an F2.8 lens, you'll not likely notice much difference in DOF. I've shot my Pentax 100mm F2.8 at F19 when shooting closeups of flowers or insects and STILL gotten a DOF of only a few millimeters... And the Sigma 180mm F3.5 I have... FUHGETABBOUTIT!!! Even at F32 it's not going to give enough DOF on a closeup of some tiny bug or something to really give complete front-to-back focus unless you luck out and have JUST THE RIGHT framing, and if you're shooting LIVE, MOVING insects and flowers, well, you just always have to take what you can get (I sometimes shoot with the pop-up flash to freeze motion so I can use the highest F-Stop possible -- I've used a ring-flash, too, but even though it SAID it would do dedicated TTL it DIDN'T -- at least not with my K-5, so I quit using it).

Ya live and learn... that's part of the challenge -- and the fun, too, I think. 


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