EF 75-300mm How to Focus at 300mm

[Styner]

Hi I have A canon rebel T3 with 75 to 300mm f/4 5.6 lens. I currently have it to 300mm . How do I get it to Focus? Because when I look in the eye piece it’s blurry 

[deebatman316]

Will the focus at other focal lengths. What happens with the lens set to manual focus. The focus ring should turn freely in manual focus. If the focus ring is hard to turn there is something broken in the lens. All of Canon's 75-300mm lenses are NOT worth repairing. It would be best to replace the lens for the 70-300mm lens @kvbarkley suggested. 

[Styner]

I’m Able to turn it by hand to the desired 300mm . But  it won’t focus . 

[deebatman316]

Are you mixing up the Focus ring with the Zoom ring. Also are you trying to turn the focus ring while the lens AF/ MF switch set to AF. Make sure the lens is set to MF before turning the focus ring. Not all lenses support Manual Focus Override. This lens Does NOT support Manual Focus Override. 

[Styner]

Do you know what lens does?

[deebatman316]

For the same zoom range look into the EF 70-300mm f/4-5.6 IS II USM Lens this lens supports manual focus override. This lens is what is called "Focus by Wire" meaning the focus ring IS NOT physically connected to the focus elements of the lens. The focus ring is connected to a digital encoder. When you half press the shutter button or use the ("AF-ON" or "*" if programmed) when turning the focus ring. The lens tells the camera which way your turning the focus ring to the camera. Then the camera sends commands to the lens AF motor to carry out manual focusing. Manual Focus will NOT if work the camera is off or the lens is unmounted. Manual Focus on this lens relies on the AF motor. Canon has 2 different types of Manual Focus Override for the EF Mount.

1. Electronic "Focus By Wire" the lens name will say "STM" or "Nano USM"
2. Mechanical Clutch under Focus Ring lens name will say USM (note some USM lenses don't support this feature. Lenses that do will have a focus distance scale window on them. True USM lenses use Ring Type USM AF Motors. Canon used to make "Micro Motor USM" these lenses DO NOT support Manual Focus Override. These lenses spin the focus ring while AF is being performed and lack a focus distance scale window.)

[Styner]

I have to set the dial to manual , and the lens to MF- @300mm it still won’t focus 

[deebatman316]

AF and MF on the lens is completely different than M mode on the camera. Set the lens to AF and the lens should AF if its working correctly. If it doesn't AF outside on a sunny day. Then there might be a problem with the lens. AF can be used in any mode on the mode dial. The mode dial doesn't control AF or MF on the lens.

[Styner]

 

 

[amfoto1]

---

@Styner wrote:

I have a canon EF 75-300mm f/4 5.5 lll telephoto zoom lens

---

The EF 75-300mm III is the least expensive telephoto zoom that Canon makes.

• It does not have image stabilization
• It uses slower, noisier micro motor auto focus
• Micro motor focusing should never be manually overridden without first turning off the AF system with the AF/MF switch. Failing to do that can damage the AF system.
• It is marginal optically, a couple examples I've seen have been particularly "soft" at the 300mm end of the zoom range (which might be what you are seeing, instead of a failure to focus?).

I agree with the other suggestions that you may want to consider an upgrade... Either of the EF 70-300mm IS USM lenses (original or II) would be an improvement in virtually every way. An EF-S 55-250mm IS STM is an alternative... another solid upgrade.

Canon lenses that aren't marked "STM" or "USM" use micro motor for focus drive. These are generally the most affordable and basic lenses they offer.

"STM" is "stepper motor" focus drive. It's much quieter, smoother and faster than micro motor. It is a "fly by wire" system, which means there is no mechanical connection to damage if you override the AF manually. However, the lens must be "powered up" to focus manually. If the camera is turned off or in sleep mode and you rotate the focus ring, nothing will happen.

"USM" stands for "ultrasonic motor" and is even faster than STM. It is quieter and smoother than micro motor, but not as quiet and smooth operating as micro motor. If shooting video, STM might be preferable over USM. But for fast action photography, USM is the best choice.

There is now also a "Nano USM" in some lenses. The EF-S 18-135mm IS USM and EF 70-300mm IS USM "II" are two examples. This is the best of both worlds.... it's fast like USM, but also quiet and smooth like STM. Works well for both video and photography.

I know of only one lens that's been made with all three types of focus drive mechanisms. The EF-S 18-135mm. The first version of it used a micro motor. Later it was improved optically and got STM focus drive. I haven't seen any claims about how much this improved AF responsiveness, but you can rest assured it was significant. Finally the EF-S 18-135mm IS USM with the new Nano iteration was introduced, which Canon claims is 2X to 4X faster focusing than the STM lens. This last version is also the only lens that can optionally be fitted with a separately sold PZ-E1 "Power Zoom" module, which might be wanted for video work.

Note: There have been a number of EF 75-300mm versions, including some with both IS and USM. However, they have been the most affordable tele zooms and all seem to suffer from mediocre optical quality. There also have been a number of different versions of EF 70-300mm. In addition to the original EF 70-300mm IS USM and the "II", there also have been premium "L" series and "DO" versions. Any of the four are a solid upgrade over any of the EF 75-300mm  lenses. FYI, the EF 70-300mm IS USM "L" is larger, heavier, more sturdy and painted off-white, better sealed for weather resistance, able to be fitted with a tripod mounting ring (optional, sold separately). The "DO" in EF 70-300mm IS USM "DO" stands for "diffractive optics", which use a special optical design that lets a lens be a lot more compact and in some cases lighter weight. Before it was discontinued, this was the most expensive 70-300mm lens Canon offered. While it's noticeably more compact than the other 70-300s, it actually isn't any lighter weight than the two "non L" versions. 

All these EF 70-300mm have sold extensively and are widely available on the used market. Only the EF 70-300mm IS USM "II" is still being offered new. The other three have been discontinued.

I just did a quick check of a couple of the better used equipment dealers and found the original EF 70-300mm IS USM selling for about the same or less than a new EF 75-300mm III costs. Shop around: B&H Photo, Adorama, KEH.com, MPB.com, Roberts Camera *usedphotopro.com) and a few others are reliable sources of used gear. B&H, Adorama and Roberts are also authorized Canon dealers offering new lenses, if you prefer.

You might find Bryan Carnathan's website helpful for information about Canon lenses and cameras.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2), EOS M5, some other cameras, various lenses & accessories
FLICKR

[Styner]

Thank you