Will diopter correction lens alter focus?

[jim_gardner4]

<p>I have just ordered a Hasselblad PME51 45 degree metered prism for use on a 503CW. The prism has a diopter correction lens fitted but I am told the correction amount is so small, anyone who doesnt need it can still focus normally with it.</p>

<p>So my question is, can this correction lens alter the lens focus? i.e if a very strong correction lens was fitted, would someone who doesnt need it be focusing the camera in a different place because their eyes are having to alter focus on the screen?</p>

<p>I hope that makes sense. Thanks in advance.</p>

<p> </p>

[mukul_dube]

<p>The two lenses -- one for vision correction, the other for making images -- are not related. The camera lens puts its image on a focussing screen, the diopter enables the user to see that screen clearly. I should think you will be able to remove the correction lens. Such things are optional accessories: although I do not know about Hasselblads.</p>

[john_stockdale2]

<p>I don't know about Hasselblad, but the similar 45 degree prism for the Rolleiflex SL66 (an SLR) has as standard a strong positive lens at the eyepiece (something like +11 diopter). A person who needs correction to focus correctly because of eyesight deficiency (short or long sight) had to buy a different version of that strong lens, maybe +10 or +9 for moderate short sight for example. For that camera they are not available.</p>

<p>If the Hasselblad arrangement is similar, the situation could be a problem for you. Sellers can be overly optimistic and have lower standards. For me, I need -1 to view my SL66 and it's unavailable. The result is that I can't focus critically without my eyeglasses. (Every other camera I have is fitted with a minus diopter as I prefer to not wear my eyeglasses when photographing.) Many would consider -1 to be a very minor correction but it makes a difference. The result is that it's not posssible to adjust focus critically because you can't see the ground glass perfectly in focus. I can get pretty close but focusing is not crisp.</p>

<p>I bought a Rolleiflex TLR and the magnifier in the flip out WLF had an extreme correction for someone very far sighted. I had to battle with the vendor (a business) to get a standard one supplied.</p>

<p>Let us know how it goes. I would be reluctant to buy something without the standard eyepiece in case I wanted to sell it later. I suppose the good thing is that for the Hasselblad the right standard eyepiece is probably not hard to source.</p>

[q.g._de_bakker]

It's like Mukul said: the correction lens will not have an effect on the camera lens' focus, only on how well you can see the focussing screen.<br>Even if you don't see the screen as well as you could, as long as you can judge wether the image on it gets better or worse, 'focus-wise', there is no real problem. An inconvenience perhaps.<br>So don't panic!<br><br>Late models of the older (i.e. pre PME45 and PME90, which have adjustable diopters) Hasselblad PME series came off-factory with a slight positive (+) correction. That helps see the viewfinder display in the 200-series cameras more clearly. It will also affect how you see the screen (both are not quite at the same virtual viewing distance), but only a bit, still well within the range healthy (i.e. young...) eyes can cope with simply by focusing.<br><br>If the eyepiece turns out to be too much for your eyes to look trhough without too much strain, you can get an optician to order and make a replacement lens that will suit you for little money.<br>If it does not say on the thing what power the corrected eyepiece is (which it probably will) you can find out what power it needs to be by trying different power lenses added (provisionally, i.e. held in place) to the eyepiece until you find one that make sthe screen look sharpest, then measure the power of the lens in the eyepiece (which will take an optician 3 seconds to do), and then add or subtract the right additional lens' power form the measured power.<br>Sounds more complicated than it is. And costs will be in the neighbourhood of US$ 30.<br><br>If that should not work for you, you could always try to find an 'original' Hasselblad neutral eypiece for the finder.

[jim_gardner4]

<p>Thanks all for the replys. I will try it when it turns up and possibly try and find a "neutral" lens for it. This is proving difficult in the UK so may also try optitians as QG suggests.</p>

[Ed_Ingold]

<p>Hasselblad screens are transparent enough that you can see through the screen when focusing. Make sure your eye is focused on the screen itself, using grid marks or the Fresnel lens "rings" as a guide. Some people like the split-prism "rangefinder" screens.</p>

[q.g._de_bakker]

Just to put clarify a thing:<br>Hasselblad screens are not really transparant enough to see through when focussing.<br>The 'plain-old' screens have a matted surface, which, by scattering the incident light, forms a rather well defined image plane. The later Acute Matte and Acute Matte D screens, however, are not scatter-type screens (only a bit, the D more so than the non-D), but contain myriads of tiny optical elements, that direct light towards the eye instead of scattering it in all directions (making them appear brighter), but (simplified a bit) which also produce an image that has some depth, and your eye can focus to anywhere inside that depth of focus making focus possible less distinct. (The old style's scatter screen's image plane has some depth too, but that's negligible, both in comparison and for all practical purposes in itself too.)<br>Being brighter helps focusing in low light a lot. But the aids on the screen (reference cross or grid lines, perhaps a split image rangefinder) become more important to aid the eye in finding the right plane to focus on.<br>The optical nature of the Acute Mattes also renders the out of focus bits a bit different from how they are captured on film.

[mikaelohlen]

Hello, I just bought a PME90 for my 205FCC. I think I have the need of buying a correction lens for it. Hasselblad 42450 plus. Trying to find one on Ebay. Does anyone know if that is a lens in itself or if it's just a distance ring between the PME90 and its regular eye piece?