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What DSLR focus better for a prescription eyeglasses wearer ?
Hi all,.

I'm wearing a prescription eyeglasses (-), and it might not accurate anymore. I have a plan to move to a DSLR soon. Do you think I can use manual focus on DSLR optimally ? Or I'd better stick to AF. Any thoughts would be appreciate...

Comments (13)

Many optical viewfinders on DSLRs have a diopter adjustment so you can view the scene and data clearly with or without glasses.Regards,Hank..

Comment #1

Yes, the diopter adjustment dials work pretty well. But I almost never try to manually focus my DSLRs. Why? Because it's not easy to do quickly and accurately..

DSLRs compare poorly with most film cameras in this respect. I had a Pentax SLR with a microprism focussing aid, my Nikons had a split-image spot on the groundglass, the Bronica had a large groundglass with a magnifier, etc. DSLR's that I've used provide no focussing aids and are generally plagued with small, and relatively dim, viewfinder images. Manual focussing is do-able (not easy) in good light, but very difficult in less well lit venues. Slow kit lenses exacerbate the situation (ie: even darker viewfinder image)...

Comment #2

Dealova wrote:.

I'm wearing a prescription eyeglasses (-), and it might not accurate anymore..

The accuracy of your prescription doesn't matter to focus. If your prescription is off, it just means that when you get the image into focus it might still not look sharp to you. But out of focus it'll be even *more* blurryyou just adjust until it's the least blurry..

As others have noted, most modern SLRs and DSLRs have an adjustable "diopter" setting that can compensate for your prescription being slightly off..

One thing to pay attention to is the viewfinder's "eyepoint" (sometimes called "eye relief") specification. This tells how far the eye can be from the viewfinder and still see everything. The higher the better, for the eyeglass wearer. Some sample entry-level DSLR figures:" Canon XTi/400D: 21mm" Sony A100: 20mm" Nikon D40x: 18mm" Olympus E-510: 14mm" Pentax K100D: not specified, reported to be very short.

Do you think I can use manual focus on DSLR optimally ? .

Autofocus SLRs, including the DSLRs, generally are designed with the expectation that you'll use autofocus. The focus screens are not designed for easy manual focus, and the lenses are often not designed for easy manual focus..

If you want to do manual focus on a regular basis, you'll need to replace your focus screen with one that is suitable for manual focus and you'll need to pick lenses that are easy to focus manually...

Comment #3

Many years ago I had a Pentax Spotamatic with manual focus, and I remember clearly how well it focused. I now shoot a Canon XT, and the manual focus is nowhere near as good. Don't get me wrong, it works; however, it is not as easy to determine what perfect focus is. I wear corrective glasses, but I also did when I used the Spotamatic. Nowadays, I use AF except in special situations..

Having said that, I really like my current camera..

Best of luck..

Jerryhttp://jchoate.zenfolio.com/..

Comment #4

Autofocus SLRs, including the DSLRs, generally are designed with theexpectation that you'll use autofocus. The focus screens are notdesigned for easy manual focus, and the lenses are often not designedfor easy manual focus..

What passes for manual focus these days is prefocusing on auto, then switching to manual so the focus doesn't change..

I agree that eye relief is very important. Diopters don't matter much as long as your eyeglasses/contacts are correct...

Comment #5

Hi,.

I have a Canon Rebel XT and have had problems focusing manually as well. It ALWAYS seems off in the viewfinder and the results are never sharp in the actual photographs..

I went back to the store where I bought my camera + lens and the salesperson said that the manual focus option on digital cameras is NOT recommended. Why? Something about digital cameras not being able to precisely match the way you have adjusted the dioptric adjustment knob to match your vision. The salesman mentioned that with the digital cameras, the best results are with automatic focus. It's true that I have gotten better results with automatic focus, but it makes no sense at all....

Does anyone know more about this?Is this really a problem with all digital cameras?.

Why do pros still use manual focus then? Is there a way around this manual focus problem?.

Your input is most appreciated...

Comment #6

Talula wrote:.

I went back to the store where I bought my camera + lens and thesalesperson said that the manual focus option on digital cameras isNOT recommended. Why? Something about digital cameras not being ableto precisely match the way you have adjusted the dioptric adjustmentknob to match your vision..

This is not correct. The dioptric adjustment only determines how sharp the focus screen looks to you. It does not determine how sharp the image that the lens projects on the focus screen is. If the dioptric adjustment is off, then you won't see anything sharp through the viewfinder, but when the part of the image that you're focusing on looks the least blurry, it's in focus..

Is this really a problem with all digital cameras?.

It's not really "digital cameras", it's "autofocus cameras". AF cameras and lenses are designed for easy AF, and they don't really worry much about manual focus..

One example: in the more than 20 years that Canon has made EOS DSLRsboth film and digitalonly one model came with a focus screen with manual focusing aids. That was the Canon EF-M, which was the only EOS camera that didn't have autofocus..

Autofocus lenses generally put the manual focus ring somewhere that the photographer won't be touching it, so that it's free to move when the camera operates the autofocus. That usually means way out at the end of the barrel. Some lens AF motor designs such as Canon's Ring USM don't turn the focusing ring during AF; these lenses can have the manual focus ring at the photographer's fingertips..

Is there a way around this manual focus problem?.

I bought a split-image focus screen for my DSLR. My lens has Ring USM, which means that it has a focusing ring at my fingertips, a distance scale if I want to use that, and Full-Time Manual focusing capabilities. I use manual focus for over half of my work, and it works fine for me...

Comment #7

Is there a way around this manual focus problem?.

I bought a split-image focus screen for my DSLR. My lens has RingUSM, which means that it has a focusing ring at my fingertips, adistance scale if I want to use that, and Full-Time Manual focusingcapabilities. I use manual focus for over half of my work, and itworks fine for me..

How much was the split-image focus screen, and how does it work?..

Comment #8

Blinkjona wrote:.

How much was the split-image focus screen.

There are two main supplier for manual focus screens for DSLRs:Haoda: http://www.haodascreen.com/Katz Eye: http://www.keoptics.com/.

Haoda generally sells standard split-image focus screens, while Katz Eye's screens generally offer upgraded features like working at higher f-numbers without blackout (important if you use teleconverters) or grid line options& at a higher cost, of course..

There are also a number of suppliers on eBay, generally less expensive. Haoda and Katz Eye both have excellent reputations for customer service; but then, I haven't heard any complaints about the eBay vendors either...

Comment #9

Doug Pardee wrote:.

Talula wrote:.

Is this really a problem with all digital cameras?.

It's not really "digital cameras", it's "autofocus cameras". AFcameras and lenses are designed for easy AF, and they don't reallyworry much about manual focus..

It is "digital cameras" - at least partly. Because most of them have sensors which are significantly smaller than 35 mm film, the image has to be enlarged to 'fill' the viewfinder and that makes it darker and thus harder to see when trying to focus. In an effort to alleviate this, the typical modern focusing screen has a surface which is designed to look pleasingly 'bright' but at the expense of clarity. This is good when using autofocus, but bad for MF..

Another factor is that many of the lower-cost digital SLRs use mirrors inside the viewfinder, instead of the traditional and superior pentaprism. This too makes the image darker, but this is neither the fault of digital nor of autofocus - it is simply cheaper..

I was considering investing in a different focusing screen for my 400D to help with manual focus, but I've decided to wait until I upgrade to the 40D. The bigger, brighter viewfinder and the properly interchangeable screens will make it a more viable proposition I think...

Comment #10

Doug Pardee wrote:.

Autofocus SLRs, including the DSLRs, generally are designed with theexpectation that you'll use autofocus. The focus screens are notdesigned for easy manual focus, and the lenses are often not designedfor easy manual focus..

If you want to do manual focus on a regular basis, you'll need toreplace your focus screen with one that is suitable for manual focusand you'll need to pick lenses that are easy to focus manually..

I wear strong glasses, such that I need to wear them to use a camera. I can't see anything through the viewfinder no matter how much I adjust the diopter. And I also have cataracts..

I've found that it is possible to do manual focus on a DSLR, but you need to choose your equipment carefully. First, different DSLRs have viewfinders with different sizes and different brightnesses. Some DSLR viewfinders are small and dim. Others are large and bright..

It used to be that the only way to get a viewfinder that was big and bright was to get an expensive full frame camera. But lately some newer (affordable) APC sensor DSLRs have viewfinders that are larger and brighter. Check out the comments in the DPReview reviews for the Canon 40D, for instance. And in the pre-review for the Canon 450D..

I have an older Canon 20D. Its viewfinder isn't as large and bright as the 40D's but it is larger and brighter than the viewfinder in the cheaper Canon Digital Rebels..

The second important thing is the lens. There are two characteristics of the lens that affect how easy it is to do manual focus: how fast it is (fast lenses let more light into the viewfinder) and how much travel there is in he manual focus adjustment dial..

Determining a lens's fastness is easyit is part of it's name. The smaller the f stop, the faster. But determining the amount of focus adjustment is more difficult. As a rule, cheap lenses have a small amount of travel and are correspondingly more difficult to focus manually..

I used to think that I couldn't focus manually, mainly because of my eyesight situation. But when I got a Canon 17-55 f/2.8 IS lens, I discovered that I could reliably manually focus with this lens on my 20D. The main thing was that the focus adjustment dial had enough travel that I could easily see when focus went in and out of focus as I adjusted it..

By point of comparison, the focusing dial on the (much) cheaper "kit" 18-55 lens is the lens barrel itselfthere is no travel at all and manual focusing is next to impossible because a very small adjustment in manual focus makes a large difference in the focus..

I don't know for sure because I don't have a hands on experience with a lot of lenses, but I think that focus dial adjustment travel goes hand and hand with expensethey don't put any effort into gearing longer travel in cheap lenses. They figure that the users will only use AF. And gearing costs money..

I've never replaced my focus screen. I use the stock screen that came with my 20D. I have no doubt that Doug is correct: that an aftermarket screen will improve manual focus ability. But manual focus is possible with the stock screen. From a person with poor eyesight that wears "Coke bottle" eyeglasses..

Wayne..

Comment #11

Wayne Larmon wrote:.

I don't know for sure because I don't have a hands on experience witha lot of lenses, but I think that focus dial adjustment travel goeshand and hand with expensethey don't put any effort into gearinglonger travel in cheap lenses. They figure that the users will onlyuse AF. And gearing costs money..

Generally speaking, lenses with ring USM are good for both autofocus and manual. In practice this means all the L lenses and some of the better ordinary lenses such as your 17-55/2.8 IS..

The cheaper lenses get some of their focusing speed by using a very short travel so the motor doesn't have to move as fast - so you are right, there is a cost factor in this...

Comment #12

Live View feature will let you focus manually by examining the image on the camera's LCD screen, much larger than the viewfinder image and zoomable. Not suitable for a quick shooting style, though...

Comment #13

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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